Important Psychologists

Important Psychologists

Famous Psychologists Throughout History

If most of us were asked to name a famous psychologist, many of us might name a televised practitioner of today, Like Dr. Phil and yes, Dr. Phil does have a doctorate in psychology.

Many psychologists throughout history deserve recognition. People like Dr. Phil have done a lot to help to bring the importance of psychology to the public sphere, but the science goes back a long time. There have been many people that have worked to establish the field as we know it today.

Important "Pre-Psychologists"

Before we start to name well-known psychologists throughout history, it's important to talk a little bit about psychology's "prehistory."

The early seeds of Western psychology took root in Greece in the fifth and fourth centuries BCE. During this time, philosophers began to pose that humans determined their actions, rather than having their actions determined by the gods. If you believed in predestination, as most people did at that time, there wasn't a whole lot of use in asking why people did what they did. During this time people adhered to the belief that gods influenced our actions, but that we ultimately chose our paths. These beliefs allowed thinkers of antiquity to ask questions about why we make decisions and what kinds of decisions we should make.

Philosophers or early ethicists largely asked questions about why we do what we do. Aristotle is usually recognized as the first one to dive into questions outside of the existing natural sciences like physics and basic biology, though his teacher Plato and Socrates before him were already asking questions like these.

In the Seventeenth century, the French philosopher René Descartes created the idea of "dualism," which held that the mind and body were composed of different substances and worked together to formulate the perception of experience. This fit with the idea that people who had what would now be called mental conditions or disabilities suffered from some physiological imbalance.

Regardless of what one believed caused these problems, most people dealt with them in one of two ways. The wealthy could attempt to cure their loved ones but more often saw that they were simply kept out of trouble. Many who struggled with mental health issues usually ended up in prison.

In the following century, another Frenchman named Philippe Pinel worked to secure comfortable housing and care for these individuals rather than leaving them in prison. During his later lifetime, Pinel would finally see the beginnings of modern psychology as a branch of the natural sciences.

Marmaduke Sampson And The Natural Scientists

In the nineteenth century, a focus on what was called the "natural sciences" sought to break up complex or abstract ideas and tie them to more manageable or malleable physical artifacts. This idea impacted many sciences and created the forerunner of modern psychology called "phrenology." Phrenologists like Marmaduke Sampson held that they could make predictions about a person's mental health and attitudes by studying the shape of their head. While this seems ridiculous now, it was close to the more modern idea of studying regions of the brain.

Willhelm Wundt

Willhelm Wundt was a German physiologist living shortly after Sampson. Wundt was also interested in applying the methods of the day to the problem of emotional and mental wellness. Instead of the natural sciences approach, he used the scientific method.

His more cautious and deliberate approach to studying mental health and wellness led him to make less inflammatory claims than other scientists of the day. Wundt established the schools of structuralism and introspection, both of which are still commonly in use today.

William James, The Father Of Psychology

Shortly after Wundt's time, William James developed a new approach. James was an American who taught the first psychology classes and is sometimes called "the father of psychology." His classes taught that the human mind was an evolutionary device that allowed us to exist and thrive as a species and that its three main functions were thinking, feeling, and remembering.

The German Gestalt Psychologists

Two years after the death of James in 1910, the school of Gestalt Psychology was taking off in Germany. Meant to help people rather than simply study them, the Gestalt school was founded by Max Wertheimer, Kurt Koffka and Wolfgang Köhler.

The idea is based on the premise that our perception of an event is more complicated than the event itself and encourages individuals to focus on their feelings about a topic and why they might be feeling that way while grounding themselves in the facts of what they perceived. It would become an important forerunner of later psychoanalytic techniques.

Gestalt psychology and its related therapeutic approaches were expanded on by later psychologists and continue to be studied and applied today.

Freud, Rorschach, And Jung: The Early Psychoanalysts

The psychoanalytic technique would be pioneered in the coming decades by Sigmund Freud and his student Carl Jung.

Freud famously suggested that our actions and attitudes are the result of our subconscious - thoughts and feelings that we are unable or unwilling to confront directly. The subconscious, according to Freud, was largely formed during experiences and relationships in childhood. It could be best understood through dreams or "free association" - the practice of hearing a word and saying the first word that came to mind and then attempting to discern how your mind connected or related the two words.

The idea of free association was further pioneered by Freud's contemporary, Hermann Rorschach of Switzerland. Rorschach's famous inkblot tests worked like Freud's word association but instead of starting with a word they would start with an inkblot. The subject would then say what they thought the inkblot looked like.

Jung studied under Freud and agreed that there was more going on in the subconscious mind than in the conscious mind. His methods of interacting with and understanding the subconscious mind differed from Freud's.

Jung continued and greatly expanded on Freud's work with dreams. Jung further suggested the idea that dreams could be interpreted with a standard dictionary of symbols because some symbols have identical or similar meaning across cultures and experiences. Jung would even go so far as to propose that all humans share a "collective unconscious" that is the root of shared symbols as well as shared ideas across cultures. The idea is often explained with the analogy of mushrooms. Some species of mushrooms grow individual caps that share a common root system deep underground.

While Jung's idea of a collective unconscious is a bit too "far out" for many people, his ideas on dream and symbol interpretation remain influential today.

John Watson And The Behaviorists

While people like Freud, Rorschach, Jung, and Maslow were making huge strides in psychology by recording and attempting to understand unseen processes of the mind, another school of psychology called "Behaviorism" tried to deal exclusively with what could be physically observed in some way. Behaviorists often discounted subjective ideas like perception dream interpretation.

Watson was largely inspired by the Russian scientist, Ivan Pavlov, whose famous experiments helped us to understand conditioning. Some of Watson's most significant contributions involved learning about the physical changes of the brain during development.

The most recent influential behaviorist is the famous psychologist B.F. Skinner. Skinner studied reinforcement in learning, believing that it was most efficient when lessons were rewarded.

Jean Piaget

While the drier approach of the behaviorists was getting at the idea of how we learn and how learning influences behavior, another branch of psychology called Cognitive Psychology was devoting itself to that study.

One of the founders, Jean Piaget, was roughly contemporary with Skinner. Piaget studied under Jung for a short time and made a study of errors in which he would try to determine the reasoning that went into common mistakes. He also studied the stages in which people comprehend large ideas by starting with smaller concepts and compounding them.

How To Learn More

People like Piaget and Skinner bring us into the late twentieth century, within the living memory of most of our readers. There are still great strides being made in psychology today. This is an incomplete list, even though it begins with thinkers who predate the formalization of psychology as we know it today. This is due to the ongoing contributions of researchers in the present day and the contributions of those outside the field, like those that Ivan Pavlov, a physiologist made.

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Wilhelm Wundt (1832–1920) was a German scientist who was the first person to be referred to as a psychologist. His famous book entitled Principles of Physiological Psychology was published in 1873. Wundt viewed psychology as a scientific study of conscious experience, and he believed that the goal of psychology was to identify components of consciousness and how those components combined to result in our conscious experience. Wundt used introspection (he called it “internal perception”), a process by which someone examines their own conscious experience as objectively as possible, making the human mind like any other aspect of nature that a scientist observed. Wundt’s version of introspection used only very specific experimental conditions in which an external stimulus was designed to produce a scientifically observable (repeatable) experience of the mind (Danziger, 1980). The first stringent requirement was the use of “trained” or practiced observers, who could immediately observe and report a reaction. The second requirement was the use of repeatable stimuli that always produced the same experience in the subject and allowed the subject to expect and thus be fully attentive to the inner reaction. These experimental requirements were put in place to eliminate “interpretation” in the reporting of internal experiences and to counter the argument that there is no way to know that an individual is observing their mind or consciousness accurately, since it cannot be seen by any other person. This attempt to understand the structure or characteristics of the mind was known as structuralism . Wundt established his psychology laboratory at the University at Leipzig in 1879. In this laboratory, Wundt and his students conducted experiments on, for example, reaction times. A subject, sometimes in a room isolated from the scientist, would receive a stimulus such as a light, image, or sound. The subject’s reaction to the stimulus would be to push a button, and an apparatus would record the time to reaction. Wundt could measure reaction time to one-thousandth of a second (Nicolas & Ferrand, 1999).

(a) Wilhelm Wundt is credited as one of the founders of psychology. He created the first laboratory for psychological research. (b) This photo shows him seated and surrounded by fellow researchers and equipment in his laboratory in Germany.

However, despite his efforts to train individuals in the process of introspection, this process remained highly subjective, and there was very little agreement between individuals. As a result, structuralism fell out of favor with the passing of Wundt’s student, Edward Titchener, in 1927 (Gordon, 1995).

Background: Philosophy and Physiology

While psychology did not emerge as a separate discipline until the late 1800s, its earliest history can be traced back to the time of the early Greeks. During the 17th-century, the French philosopher Rene Descartes introduced the idea of dualism, which asserted that the mind and body were two entities that interact to form the human experience.  

Many other issues still debated by psychologists today, such as the relative contributions of nature vs. nurture, are rooted in these early philosophical traditions.

So what makes psychology different from philosophy? While early philosophers relied on methods such as observation and logic, today’s psychologists utilize scientific methodologies to study and draw conclusions about human thought and behavior.

Physiology also contributed to psychology’s eventual emergence as a scientific discipline. Early physiological research on the brain and behavior had a dramatic impact on psychology, ultimately contributing to applying scientific methodologies to the study of human thought and behavior.

Important Dates in the History of Psychology

There are many important events that have had a powerful influence on the history of psychology. The following are just a few important dates in psychology that mark significant events and milestones.

On February 24, 1913, John B. Watson delivered his lecture, Psychology as the Behaviorist Views It, at a meeting of the American Psychological Association (APA).

On February 26, 1907, psychologist John Bowlby was born. His research on attachment theory contributed greatly to developmental psychology.

On February 27, 1859, Bertha Pappenheim was born. Famously known as Anna O., she became one of Sigmund Freud’s most famous case studies.

On March 3, 1908, John B. Watson became a faculty member at John Hopkins University, with a starting salary of $3,000 a year.

On March 4, 1916, Hans Eysenck was born. Eysenck went on to become one of the most frequently cited psychologists as well as a controversial and much-criticized figure because of his view that racial differences in intelligence were due to heritability.

On March 5, 1934, psychologist Daniel Kahneman was born. Kahneman and his colleague Amos Tversky were later awarded a Nobel Prize in Economics for their work in prospect theory.

On March 8, 1883, G. Stanley Hall created the first American psychology lab at John Hopkins University.

On March 8, 1971, the U.S. Supreme Court ruled that the unnecessary use of intelligence testing in employment screening was unconstitutional.

On March 9, 1758, Franz Joseph Gall was born. Gall developed phrenology, which suggested that personality traits were related to the shape of the head. While phrenology is dismissed as a pseudoscience today, it actually had an important impact on modern neuroscience by inspiring research on brain localization.

On March 10, 1937, B.F. Skinner became a member of Psi Chi, the national honor society in psychology.

On March 12, 1986, the journal Psychology and Aging was first published. The journal, published by the American Psychological Association, offers articles and research on adult development and aging.

On March 13, 1964, Kitty Genovese was murdered outside her apartment in New York City. Despite the presence of nearly 30 witnesses, no one tried to assist her. Her death led to numerous studies on the bystander effect. Later research has shown that many of the original “witnesses” did not know that she was being murdered and did not have a clear view of what was taking place.

On March 15, 1938, Sigmund Freud’s home in Vienna was taken over by Nazis. Freud was interrogated by the Gestapo and many of his books from his home and the Vienna library were later burned. Freud later escaped to London, but all four of his elderly sisters were killed in Nazi concentration camps.

On April 6, 1956, Psychological Science published George A. Miller’s well-known article on human memory, “The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Information Processing.”

On April 11, 1906, Sigmund Freud began his correspondence with Carl Jung. While Freud viewed Jung as a protégé for several years, theoretical differences eventually contributed to an end to their friendship and correspondence.

On April 14, 1886, Edward C. Tolman was born. A student of Hugo Munsterberg, Tolman is known today as a cognitive behaviorist. He is best-known for his theory of “purposive behaviorism,” which combined elements of cognitive psychology with behavioral theories of learning.

On April 14 1952, Romania issued a stamp honoring physiologist Ivan Pavlov.

On April 15, 1880, Max Wertheimer was born. Wertheimer was one of the founders of Gesalt psychology and introduced the Gestalt laws of perceptual organization.

On March 11, 1988, the American Psychological Association sold the magazine Psychology Today for $6.5 million, after losing nearly $16 million in five years of ownership.

On May 13, 1893, psychologist Henry A. Murray was born. Murray is known for his theory of psychogenic needs.

On May 14, 1951, the results of Solomon Asch’s famous conformity studies were published in Harold Guetzkow’s Groups, Leadership, and Men.

On May 15, 1848, Carl Wernicke was born. He is known for his research on the effects of brain disease on speech and language and his discovery that damage to an area of the temporal lobe (now known as Wernicke’s area) is associated with what is now called Wernicke’s aphasia.

On May 16, 1938, Abraham A. Brill published The Basic Writings of Sigmund Freud.

On April 22, 1899, William James published his book Talks to Teachers. The book was composed of 10 lectures that were originally presented at Harvard University in 1891 and 1892. Psychologist and philosopher William James is often referred to as the father of American psychology.

On June 26, 1878, G. Stanley Hall earned his PhD in Psychology from Harvard University, becoming the first person to earn a doctorate in psychology from a U.S. university.

On July 12, 1882, famous psychotherapy patient Anna O. was transferred from the care of her therapist, Josef Breuer, to a sanatorium in Switzerland.

On November 22, 1919, John B. Watson’s book Psychology, From the Standpoint of a Behaviorist was published. Watson’s argument that psychology should focus on the study of behavior was a significant change from earlier introspective methods and contributed greatly to the rise of behaviorism.

On December 27, 1571, Johannes Kepler was born. Kepler first proposed that the retina was the location of visual reception.

On December 27, 1791, the state of Maryland first allocated funds for the care of individuals with mental illnesses.

On December 27, 1892, the American Psychological Association held its first annual meeting at the University of Pennsylvania.

Psychology Degree

One of the most complex and interesting fields of study is psychology. The human mind is an interesting place, that we’re only just beginning to understand. Over the last 100 years, though, we have made great strides as a society in understanding what goes on inside the mind.

There are plenty of famous clinical psychologists who have helped us open up the mind and begin to solve some of its mysteries. If you are looking to get a psychology degree, chances are that you will study the work of many psychologists, including these 10 famous clinical psychologists:

  1. Sigmund Freud: Everyone knows who Sigmund Freud is. This Austrian philosopher and psychologist is known as the founder of modern psychoanalysis. Freud’s theories have provided a basis for modern clinical psychology, and even provided a basis for a great deal of controversy. With one of his colleagues, Joseph Breuer, he was among the first to conceive of the study of the mind and psyche. He developed several therapy techniques that are still in use today, and Freud’s concepts have made him a household name.
  2. Carl Jung: Swiss psychiatrist Carl Jung is known as the founder of analytical psychology. He had a deep interest in religion, and its effect on the psyche. Jung also pioneered the idea of dream analysis, and used dreams as part of his clinical therapy approach. He considered himself a natural scientist, and observed the development of people. One of Jung’s most interesting concepts considers the way that people become individuals — and the way that they become “whole” people. Jung is one of the most well-known clinical psychologists.
  3. B.F. Skinner: You’ve probably heard of the Skinner box — device meant to help with operant conditioning. B.F. Skinner is known as the founder of modern behaviorism in psychology. He studied how to get people to behave in certain ways, performing famous experiments. Skinner was the founder of experimental research psychology, a branch that looked how to change people’s behavior through different types of therapy. Interestingly, Skinner was also a poet and inventor.
  4. Carl Rogers: One of the founders of humanistic psychology, Carl Rogers was known for his person-centered approach to therapy. His techniques have been used in psychotherapy and counseling as a way to focus more on the needs of the patient/client. Rogers worked with different groups in Northern Ireland and South Africa. His work garnered him a Nobel Peace Prize nomination. The techniques used by Rogers are considered influential still, and he is considered one of the most famous clinicians of the 20th century.
  5. Alfred Kinsey: If you think about the psychology of sex, you have to know about Alfred Kinsey. He became famous for really delving into sexual psychology and sexual development. His work was very influential, although considered controversial at its height in the 1940s and 1950s. Kinsey founded an institute for sex research, and it now bears its name. Many other sexologists and therapists have followed in his footsteps. There are plenty who still consider the Kinsey Reports to be profound works of psychological brilliance.
  6. Erik Erikson: One of the founders of of developmental psychology, Erik Erikson is known as a pioneer in human development. You have probably heard the term “identity crisis.” Erikson was the psychologist who invented the phrase. Interestingly, he never actually received a bachelor’s degree, even though his on of the most famous clinical psychologists of all time. He taught at Yale and Harvard, and was known for his work in social psychological development. Erikson’s son, Kai, is a famous sociologist.
  7. Jean Piaget: In terms of the “theory of knowing,” Jean Piaget is considered the pioneer. Piaget was known for his work with children, and tracking their psychological development. He worked out different theories of education, insisting that proper education for children was vital to keep societies from collapsing. His therapies and theories, as well as the epistemological studies he did with children, have made Piaget one of the most famous psychologists of all time.
  8. Albert Ellis: This clinical psychologist is known as the founder of cognitive behavioral theories. Albert Ellis developed Rational Emotive Behavior Therapy (REBT) in 1955, and this technique is still used today. His theories are widely believed to have revolutionized psychotherapy, helping the shift to behavior-based treatment. Prior to his death in 2007, Ellis was named the “greatest living psychologist” by Psychology Today. He also did work in the fields of sexology and religion.
  9. Albert Bandura: One of the pioneers in social learning was Albert Bandura. He is still alive today, and is considered the greatest living psychologist by some. Bandura’s experiments with Bobo Dolls, and learning aggressive behaviors. His development of social cognitive theory, as well as personality theories, are considered quite forward-thinking and an integral part of the shift from behaviorism to cognitive psychology. Many of Bandura’s findings are still used today by psychologists helping patients with social modeling, and with other therapies. Kay Redfield Jamison: The youngest person on this list (and the only woman) Kay Jamison is known for her work with bipolar disorder. Jamison is a clinical psychologist who centers her working on helping those with mental problems — especially bipolar disorder — effectively. Jamison has bipolar herself, and has a unique insight into the minds of her patients. She has lectured all over the world, and has authored hundreds of academic articles.

Other Famous Clinical Psychologists

There are, of course, plenty of other famous psychologists who have contributed to the field, and the study, of the human mind and behavior. Here are five more well-known psychologists:

Jean Piaget (1896-1980)

Piaget developed the first theory of child cognitive development. At the time it was groundbreaking. Before his work, children were believed to share the cognitive processes of adults. His theory directly led to the emergence of cognitive and developmental psychology. He believed cognitive development was an active process, not something that children passively acquired. Piaget coined the popular psychological phrases schema, accommodation, and assimilation. In addition, he was a fierce child advocate and fought for the education of children as vital to a society’s success.


The word psychology derives from the Greek word psyche, for spirit or soul. The latter part of the word "psychology" derives from -λογία -logia, which refers to "study" or "research". [7] The Latin word psychologia was first used by the Croatian humanist and Latinist Marko Marulić in his book, Psichiologia de ratione animae humanae in the late 15th century or early 16th century. [8] The earliest known reference to the word psychology in English was by Steven Blankaart in 1694 in The Physical Dictionary. The dictionary refers to "Anatomy, which treats the Body, and Psychology, which treats of the Soul." [9]

In 1890, William James defined psychology as "the science of mental life, both of its phenomena and their conditions." [10] This definition enjoyed widespread currency for decades. However, this meaning was contested, notably by radical behaviorists such as John B. Watson, who in his 1913 manifesto defined the discipline of psychology as the acquisition of information useful to the control of behavior. Since James defined "psychology," the term more strongly implicates scientific experimentation. [11] [12] Folk psychology refers to the understanding of ordinary people, as contrasted with that of psychology professionals. [13]

The ancient civilizations of Egypt, Greece, China, India, and Persia all engaged in the philosophical study of psychology. In Ancient Egypt the Ebers Papyrus mentioned depression and thought disorders. [14] Historians note that Greek philosophers, including Thales, Plato, and Aristotle (especially in his De Anima treatise), [15] addressed the workings of the mind. [16] As early as the 4th century BC, Greek physician Hippocrates theorized that mental disorders had physical rather than supernatural causes. [17]

In China, psychological understanding grew from the philosophical works of Laozi and Confucius, and later from the doctrines of Buddhism. This body of knowledge involves insights drawn from introspection and observation, as well as techniques for focused thinking and acting. It frames the universe in term of a division of physical reality and mental reality as well as the interaction between the physical and the mental. Chinese philosophy also emphasized purifying the mind in order to increase virtue and power. An ancient text known as The Yellow Emperor's Classic of Internal Medicine identifies the brain as the nexus of wisdom and sensation, includes theories of personality based on yin–yang balance, and analyzes mental disorder in terms of physiological and social disequilibria. Chinese scholarship that focused on the brain advanced during the Qing Dynasty with the work of Western-educated Fang Yizhi (1611–1671), Liu Zhi (1660–1730), and Wang Qingren (1768–1831). Wang Qingren emphasized the importance of the brain as the center of the nervous system, linked mental disorder with brain diseases, investigated the causes of dreams and insomnia, and advanced a theory of hemispheric lateralization in brain function. [18]

Influenced by Hinduism, Indian philosophy explored distinctions in types of awareness. A central idea of the Upanishads and other Vedic texts that formed the foundations of Hinduism was the distinction between a person's transient mundane self and their eternal, unchanging soul. Divergent Hindu doctrines and Buddhism have challenged this hierarchy of selves, but have all emphasized the importance of reaching higher awareness. Yoga encompasses a range of techniques used in pursuit of this goal. Theosophy, a religion established by Russian-American philosopher Helena Blavatsky, drew inspiration from these doctrines during her time in British India. [19] [20]

Psychology was of interest to Enlightenment thinkers in Europe. In Germany, Gottfried Wilhelm Leibniz (1646–1716) applied his principles of calculus to the mind, arguing that mental activity took place on an indivisible continuum. He suggested that the difference between conscious and unconscious awareness is only a matter of degree. Christian Wolff identified psychology as its own science, writing Psychologia Empirica in 1732 and Psychologia Rationalis in 1734. Immanuel Kant advanced the idea of anthropology as a discipline, with psychology an important subdivision. Kant, however, explicitly rejected the idea of an experimental psychology, writing that "the empirical doctrine of the soul can also never approach chemistry even as a systematic art of analysis or experimental doctrine, for in it the manifold of inner observation can be separated only by mere division in thought, and cannot then be held separate and recombined at will (but still less does another thinking subject suffer himself to be experimented upon to suit our purpose), and even observation by itself already changes and displaces the state of the observed object." In 1783, Ferdinand Ueberwasser (1752-1812) designated himself Professor of Empirical Psychology and Logic and gave lectures on scientific psychology, though these developments were soon overshadowed by the Napoleonic Wars. [21] At the end of the Napoleonic era, Prussian authorities discontinued the Old University of Münster. [22] Having consulted philosophers Hegel and Herbart, however, in 1825 the Prussian state established psychology as a mandatory discipline in its rapidly expanding and highly influential educational system. However, this discipline did not yet embrace experimentation. [23] In England, early psychology involved phrenology and the response to social problems including alcoholism, violence, and the country's crowded "lunatic" asylums. [24]

Beginning of experimental psychology

Gustav Fechner began conducting psychophysics research in Leipzig in the 1830s. He articulated the principle that human perception of a stimulus varies logarithmically according to its intensity. [25] The principle became known as the Weber–Fechner law. Fechner's 1860 Elements of Psychophysics challenged Kant's negative view with regard to conducting quantitative research on the mind. [26] [23] Fechner's achievement was to show that "mental processes could not only be given numerical magnitudes, but also that these could be measured by experimental methods." [23] In Heidelberg, Hermann von Helmholtz conducted parallel research on sensory perception, and trained physiologist Wilhelm Wundt. Wundt, in turn, came to Leipzig University, where he established the psychological laboratory that brought experimental psychology to the world. Wundt focused on breaking down mental processes into the most basic components, motivated in part by an analogy to recent advances in chemistry, and its successful investigation of the elements and structure of materials. [27] Paul Flechsig and Emil Kraepelin soon created another influential laboratory at Leipzig, a psychology-related lab, that focused more on experimental psychiatry. [23]

The German psychologist Hermann Ebbinghaus, a researcher at the University of Berlin, was another 19th-century contributor to the field. He pioneered the experimental study of memory and developed quantitative models of learning and forgetting. [28] In the early twentieth century, Wolfgang Kohler, Max Wertheimer, and Kurt Koffka co-founded the school of Gestalt psychology (not to be confused with the Gestalt therapy of Fritz Perls). The approach of Gestalt psychology is based upon the idea that individuals experience things as unified wholes. Rather than reducing thoughts and behavior into smaller component elements, as in structuralism, the Gestaltists maintained that whole of experience is important, and differs from the sum of its parts.

Psychologists in Germany, Denmark, Austria, England, and the United States soon followed Wundt in setting up laboratories. [29] G. Stanley Hall, an American who studied with Wundt, founded a psychology lab that became internationally influential. The lab was located at Johns Hopkins University. Hall, in turn, trained Yujiro Motora, who brought experimental psychology, emphasizing psychophysics, to the Imperial University of Tokyo. [30] Wundt's assistant, Hugo Münsterberg, taught psychology at Harvard to students such as Narendra Nath Sen Gupta—who, in 1905, founded a psychology department and laboratory at the University of Calcutta. [19] Wundt's students Walter Dill Scott, Lightner Witmer, and James McKeen Cattell worked on developing tests of mental ability. Cattell, who also studied with eugenicist Francis Galton, went on to found the Psychological Corporation. Witmer focused on the mental testing of children Scott, on employee selection. [31]

Another student of Wundt, the Englishman Edward Titchener, created the psychology program at Cornell University and advanced "structuralist" psychology. The idea behind structuralism was to analyze and classify different aspects of the mind, primarily through the method of introspection. [32] William James, John Dewey, and Harvey Carr advanced the idea of functionalism, an expansive approach to psychology that underlined the Darwinian idea of a behavior's usefulness to the individual. In 1890, James wrote an influential book, The Principles of Psychology, which expanded on the structuralism. He memorably described "stream of consciousness." James's ideas interested many American students in the emerging discipline. [32] [33] [34] Dewey integrated psychology with societal concerns, most notably by promoting progressive education, inculcating moral values in children, and assimilating immigrants. [35]

A different strain of experimentalism, with a greater connection to physiology, emerged in South America, under the leadership of Horacio G. Piñero at the University of Buenos Aires. [36] In Russia, too, researchers placed greater emphasis on the biological basis for psychology, beginning with Ivan Sechenov's 1873 essay, "Who Is to Develop Psychology and How?" Sechenov advanced the idea of brain reflexes and aggressively promoted a deterministic view of human behavior. [37] The Russian-Soviet physiologist Ivan Pavlov discovered in dogs a learning process that was later termed "classical conditioning" and applied the process to human beings. [38]

Consolidation and funding

One of the earliest psychology societies was La Société de Psychologie Physiologique in France, which lasted from 1885 to 1893. The first meeting of the International Congress of Psychology sponsored by the International Union of Psychological Science took place in Paris, in August 1889, amidst the World's Fair celebrating the centennial of the French Revolution. William James was one of three Americans among the four hundred attendees. The American Psychological Association (APA) was founded soon after, in 1892. The International Congress continued to be held at different locations in Europe and with wide international participation. The Sixth Congress, held in Geneva in 1909, included presentations in Russian, Chinese, and Japanese, as well as Esperanto. After a hiatus for World War I, the Seventh Congress met in Oxford, with substantially greater participation from the war-victorious Anglo-Americans. In 1929, the Congress took place at Yale University in New Haven, Connecticut, attended by hundreds of members of the APA. [29] Tokyo Imperial University led the way in bringing new psychology to the East. New ideas about psychology diffused from Japan into China. [18] [30]

American psychology gained status upon the U.S.'s entry into World War I. A standing committee headed by Robert Yerkes administered mental tests ("Army Alpha" and "Army Beta") to almost 1.8 million soldiers. [39] Subsequently, the Rockefeller family, via the Social Science Research Council, began to provide funding for behavioral research. [40] [41] Rockefeller charities funded the National Committee on Mental Hygiene, which disseminated the concept of mental illness and lobbied for applying ideas from psychology to child rearing. [39] [42] Through the Bureau of Social Hygiene and later funding of Alfred Kinsey, Rockefeller foundations helped establish research on sexuality in the U.S. [43] Under the influence of the Carnegie-funded Eugenics Record Office, the Draper-funded Pioneer Fund, and other institutions, the eugenics movement also influenced American psychology. In the 1910s and 1920s, eugenics became a standard topic in psychology classes. [44] In contrast to the US, in the UK psychology was met with antagonism by the scientific and medical establishments, and up until 1939, there were only six psychology chairs in universities in England. [45]

During World War II and the Cold War, the U.S. military and intelligence agencies established themselves as leading funders of psychology by way of the armed forces and in the new Office of Strategic Services intelligence agency. University of Michigan psychologist Dorwin Cartwright reported that university researchers began large-scale propaganda research in 1939–1941. He observed that "the last few months of the war saw a social psychologist become chiefly responsible for determining the week-by-week-propaganda policy for the United States Government." Cartwright also wrote that psychologists had significant roles in managing the domestic economy. [46] The Army rolled out its new General Classification Test to assess the ability of millions of soldiers. The Army also engaged in large-scale psychological research of troop morale and mental health. [47] In the 1950s, the Rockefeller Foundation and Ford Foundation collaborated with the Central Intelligence Agency (CIA) to fund research on psychological warfare. [48] In 1965, public controversy called attention to the Army's Project Camelot—the "Manhattan Project" of social science—an effort which enlisted psychologists and anthropologists to analyze the plans and policies of foreign countries for strategic purposes. [49] [50]

In Germany after World War I, psychology held institutional power through the military and subsequently expanded along with the rest of the military under the Third Reich. [23] Under the direction of Hermann Göring's cousin Matthias Göring, the Berlin Psychoanalytic Institute was renamed the Göring Institute. Freudian psychoanalysts were expelled and persecuted under the anti-Jewish policies of the Nazi Party, and all psychologists had to distance themselves from Freud and Adler, founders of psychoanalysis who were also Jewish. [51] The Göring Institute was well-financed throughout the war with a mandate to create a "New German Psychotherapy." This psychotherapy aimed to align suitable Germans with the overall goals of the Reich. As described by one physician, "Despite the importance of analysis, spiritual guidance and the active cooperation of the patient represent the best way to overcome individual mental problems and to subordinate them to the requirements of the Volk and the Gemeinschaft." Psychologists were to provide Seelenführung [lit., soul guidance], the leadership of the mind, to integrate people into the new vision of a German community. [52] Harald Schultz-Hencke melded psychology with the Nazi theory of biology and racial origins, criticizing psychoanalysis as a study of the weak and deformed. [53] Johannes Heinrich Schultz, a German psychologist recognized for developing the technique of autogenic training, prominently advocated sterilization and euthanasia of men considered genetically undesirable, and devised techniques for facilitating this process. [54]

After the war, new institutions were created although some psychologists, because of their Nazi affiliation, were discredited. Alexander Mitscherlich founded a prominent applied psychoanalysis journal called Psyche. With funding from the Rockefeller Foundation, Mitscherlich established the first clinical psychosomatic medicine division at Heidelberg University. In 1970, psychology was integrated into the required studies of medical students. [55]

After the Russian Revolution, the Bolsheviks promoted psychology as a way to engineer the "New Man" of socialism. Consequently, university psychology departments trained large numbers of students in psychology. At the completion of training, positions were made available for those students at schools, workplaces, cultural institutions, and in the military. The Russian state emphasized pedology and the study of child development. Lev Vygotsky became prominent in the field of child development. [37] The Bolsheviks also promoted free love and embraced the doctrine of psychoanalysis as an antidote to sexual repression. [56] Although pedology and intelligence testing fell out of favor in 1936, psychology maintained its privileged position as an instrument of the Soviet Union. [37] Stalinist purges took a heavy toll and instilled a climate of fear in the profession, as elsewhere in Soviet society. [57] Following World War II, Jewish psychologists past and present, including Lev Vygotsky, A.R. Luria, and Aron Zalkind, were denounced Ivan Pavlov (posthumously) and Stalin himself were celebrated as heroes of Soviet psychology. [58] Soviet academics experienced a degree of liberalization during the Khrushchev Thaw. The topics of cybernetics, linguistics, and genetics became acceptable again. The new field of engineering psychology emerged. The field involved the study of the mental aspects of complex jobs (such as pilot and cosmonaut). Interdisciplinary studies became popular and scholars such as Georgy Shchedrovitsky developed systems theory approaches to human behavior. [59]

Twentieth-century Chinese psychology originally modeled itself on U.S. psychology, with translations from American authors like William James, the establishment of university psychology departments and journals, and the establishment of groups including the Chinese Association of Psychological Testing (1930) and the Chinese Psychological Society (1937). Chinese psychologists were encouraged to focus on education and language learning. Chinese psychologists were drawn to the idea that education would enable modernization. John Dewey, who lectured to Chinese audiences between 1919 and 1921, had a significant influence on psychology in China. Chancellor T'sai Yuan-p'ei introduced him at Peking University as a greater thinker than Confucius. Kuo Zing-yang who received a PhD at the University of California, Berkeley, became President of Zhejiang University and popularized behaviorism. [60] After the Chinese Communist Party gained control of the country, the Stalinist Soviet Union became the major influence, with Marxism–Leninism the leading social doctrine and Pavlovian conditioning the approved means of behavior change. Chinese psychologists elaborated on Lenin's model of a "reflective" consciousness, envisioning an "active consciousness" (pinyin: tzu-chueh neng-tung-li ) able to transcend material conditions through hard work and ideological struggle. They developed a concept of "recognition" (pinyin: jen-shih ) which referred to the interface between individual perceptions and the socially accepted worldview failure to correspond with party doctrine was "incorrect recognition." [61] Psychology education was centralized under the Chinese Academy of Sciences, supervised by the State Council. In 1951, the Academy created a Psychology Research Office, which in 1956 became the Institute of Psychology. Because most leading psychologists were educated in the United States, the first concern of the Academy was the re-education of these psychologists in the Soviet doctrines. Child psychology and pedagogy for the purpose of a nationally cohesive education remained a central goal of the discipline. [62]


In 1920, Édouard Claparède and Pierre Bovet created a new applied psychology organization called the International Congress of Psychotechnics Applied to Vocational Guidance, later called the International Congress of Psychotechnics and then the International Association of Applied Psychology. [29] The IAAP is considered the oldest international psychology association. [63] Today, at least 65 international groups deal with specialized aspects of psychology. [63] In response to male predominance in the field, female psychologists in the U.S. formed the National Council of Women Psychologists in 1941. This organization became the International Council of Women Psychologists after World War II and the International Council of Psychologists in 1959. Several associations including the Association of Black Psychologists and the Asian American Psychological Association have arisen to promote the inclusion of non-European racial groups in the profession. [63]

The International Union of Psychological Science (IUPsyS) is the world federation of national psychological societies. The IUPsyS was founded in 1951 under the auspices of the United Nations Educational, Cultural and Scientific Organization (UNESCO). [29] [64] Psychology departments have since proliferated around the world, based primarily on the Euro-American model. [19] [64] Since 1966, the Union has published the International Journal of Psychology. [29] IAAP and IUPsyS agreed in 1976 each to hold a congress every four years, on a staggered basis. [63]

IUPsyS recognizes 66 national psychology associations and at least 15 others exist. [63] The American Psychological Association is the oldest and largest. [63] Its membership has increased from 5,000 in 1945 to 100,000 in the present day. [32] The APA includes 54 divisions, which since 1960 have steadily proliferated to include more specialties. Some of these divisions, such as the Society for the Psychological Study of Social Issues and the American Psychology–Law Society, began as autonomous groups. [63]

The Interamerican Psychological Society, founded in 1951, aspires to promote psychology across the Western Hemisphere. It holds the Interamerican Congress of Psychology and ha had 1,000 members in year 2000. The European Federation of Professional Psychology Associations, founded in 1981, represents 30 national associations with a total of 100,000 individual members. At least 30 other international organizations represent psychologists in different regions. [63]

In some places, governments legally regulate who can provide psychological services or represent themselves as a "psychologist." [65] The APA defines a psychologist as someone with a doctoral degree in psychology. [66]


Early practitioners of experimental psychology distinguished themselves from parapsychology, which in the late nineteenth century enjoyed popularity (including the interest of scholars such as William James). Some people considered parapsychology to be part of "psychology." Parapsychology, hypnotism, and psychism were major topics at the early International Congresses. But students of these fields were eventually ostractized, and more or less banished from the Congress in 1900–1905. [29] Parapsychology persisted for a time at Imperial University in Japan, with publications such as Clairvoyance and Thoughtography by Tomokichi Fukurai, but here too it was mostly shunned by 1913. [30]

As a discipline, psychology has long sought to fend off accusations that it is a "soft" science. Philosopher of science Thomas Kuhn's 1962 critique implied psychology overall was in a pre-paradigm state, lacking agreement on the type of overarching theory found in mature sciences such as chemistry and physics. [67] Because some areas of psychology rely on research methods such as surveys and questionnaires, critics asserted that psychology is not an objective science. Skeptics have suggested that personality, thinking, and emotion cannot be directly measured and are often inferred from subjective self-reports, which may be problematic. Experimental psychologists have devised a variety of ways to indirectly measure these elusive phenomenological entities. [68] [69] [70]

Divisions still exist within the field, with some psychologists more oriented towards the unique experiences of individual humans, which cannot be understood only as data points within a larger population. Critics inside and outside the field have argued that mainstream psychology has become increasingly dominated by a "cult of empiricism," which limits the scope of research because investigators restrict themselves to methods derived from the physical sciences. [71] Feminist critiques have argued that claims to scientific objectivity obscure the values and agenda of (historically) mostly male researchers. [39] Jean Grimshaw, for example, argues that mainstream psychological research has advanced a patriarchal agenda through its efforts to control behavior. [72]


Psychologists generally consider biology the substrate of thought and feeling, and therefore an important area of study. Behaviorial neuroscience, also known as biological psychology, involves the application of biological principles to the study of physiological and genetic mechanisms underlying behavior in humans and other animals. The allied field of comparative psychology is the scientific study of the behavior and mental processes of non-human animals. [73] A leading question in behavioral neuroscience has been whether and how mental functions are localized in the brain. From Phineas Gage to H.M. and Clive Wearing, individual people with mental deficits traceable to physical brain damage have inspired new discoveries in this area. [74] Modern behavioral neuroscience could be said to originate in the 1870s, when in France Paul Broca traced production of speech to the left frontal gyrus, thereby also demonstrating hemispheric lateralization of brain function. Soon after, Carl Wernicke identified a related area necessary for the understanding of speech. [75]

The contemporary field of behavioral neuroscience focuses on the physical basis of behavior. Behaviorial neuroscientists use animal models, often relying on rats, to study the neural, genetic, and cellular mechanisms that underlie behaviors involved in learning, memory, and fear responses. [76] Cognitive neuroscientists, by using neural imaging tools, investigate the neural correlates of psychological processes in humans. Neuropsychologists conduct psychological assessments to determine how an individual's behavior and cognition are related to the brain. The biopsychosocial model is a cross-disciplinary, holistic model that concerns the ways in which interrelationships of biological, psychological, and socio-environmental factors affect health and behavior. [77]

Evolutionary psychology approaches thought and behavior from a modern evolutionary perspective. This perspective suggests that psychological adaptations evolved to solve recurrent problems in human ancestral environments. Evolutionary psychologists attempt to find out how human psychological traits are evolved adaptations, the results of natural selection or sexual selection over the course of human evolution. [78]

The history of the biological foundations of psychology includes evidence of racism. The idea of white supremacy and indeed the modern concept of race itself arose during the process of world conquest by Europeans. [79] Carl von Linnaeus's four-fold classification of humans classifies Europeans as intelligent and severe, Americans as contented and free, Asians as ritualistic, and Africans as lazy and capricious. Race was also used to justify the construction of socially specific mental disorders such as drapetomania and dysaesthesia aethiopica—the behavior of uncooperative African slaves. [80] After the creation of experimental psychology, "ethnical psychology" emerged as a subdiscipline, based on the assumption that studying primitive races would provide an important link between animal behavior and the psychology of more evolved humans. [81]


A tenet of behavioral research is that a large part of both human and lower-animal behavior is learned. A principle associated with behavioral research is that the mechanisms involved in learning apply to humans and non-human animals. Behavioral researchers have developed a treatment known as behavior modification, which is used to help individuals replace undesirable behaviors with desirable ones.

Early behavioral researchers studied stimulus–response pairings, now known as classical conditioning. They demonstrated that when a biologically potent stimulus (e.g., food that elicits salivation) is paired with a previously neutral stimulus (e.g., a bell) over several learning trials, the neutral stimulus by itself can come to elicit the response the biologically potent stimulus elicits. Ivan Pavlov—known best for inducing dogs to salivate in the presence of a stimulus previously linked with food—became a leading figure in the Soviet Union and inspired followers to use his methods on humans. [37] In the United States, Edward Lee Thorndike initiated "connectionist" studies by trapping animals in "puzzle boxes" and rewarding them for escaping. Thorndike wrote in 1911: "There can be no moral warrant for studying man's nature unless the study will enable us to control his acts." [82] From 1910–1913 the American Psychological Association went through a sea change of opinion, away from mentalism and towards "behavioralism." In 1913 John B. Watson coined the term behaviorism for this school of thought. [83] Watson's famous Little Albert experiment in 1920 was at first thought to demonstrate that repeated use of upsetting loud noises could instill phobias (aversions to other stimuli) in an infant human, [12] [84] although such a conclusion was likely an exaggeration. [85] Karl Lashley, a close collaborator with Watson, examined biological manifestations of learning in the brain. [74]

Clark L. Hull, Edwin Guthrie, and others did much to help behaviorism become a widely used paradigm. [32] A new method of "instrumental" or "operant" conditioning added the concepts of reinforcement and punishment to the model of behavior change. Radical behaviorists avoided discussing the inner workings of the mind, especially the unconscious mind, which they considered impossible to assess scientifically. [86] Operant conditioning was first described by Miller and Kanorski and popularized in the U.S. by B.F. Skinner, who emerged as a leading intellectual of the behaviorist movement. [87] [88]

Noam Chomsky published an influential critique of radical behaviorism on the grounds that behaviorist principles could not adequately explain the complex mental process of language acquisition and language use. [89] [90] The review, which was scathing, did much to reduce the status of behaviorism within psychology. [91] Martin Seligman and his colleagues discovered that they could condition "learned helplessness" in dogs, a state that was not predicted by the behaviorist approach to psychology. [92] [93] Edward C. Tolman advanced a hybrid "cognitive behavioral" model, most notably with his 1948 publication discussing the cognitive maps used by rats to guess at the location of food at the end of a maze. [94] Skinner's behaviorism did not die, in part because it generated successful practical applications. [90]

The Association for Behavior Analysis International was founded in 1974 and by 2003 had members from 42 countries. The field has gained a foothold in Latin America and Japan. [95] Applied behavior analysis is the term used for the application of the principles of operant conditioning to change socially significant behavior (it supersedes the term behavior modification). [96]


Green Red Blue
Purple Blue Purple

Blue Purple Red
Green Purple Green

The Stroop effect is the fact that naming the color of the first set of words is easier and quicker than the second.

Cognitive psychology involves the study of mental processes, including perception, attention, language comprehension and production, memory, and problem solving. [97] Researchers in the field of cognitive psychology are sometimes called cognitivists. They rely on an information processing model of mental functioning. Cognitivist research is informed by functionalism and experimental psychology.

Starting in the 1950s, the experimental techniques developed by Wundt, James, Ebbinghaus, and others re-emerged as experimental psychology became increasingly cognitivist and, eventually, constituted a part of the wider, interdisciplinary cognitive science. [98] [99] Some called this development the cognitive revolution because it rejected the anti-mentalist dogma of behaviorism as well as the strictures of psychoanalysis. [99]

Albert Bandura helped along the transition in psychology from behaviorism to cognitive psychology. Bandura and other social learning theorists advanced the idea of vicarious learning. In other words, they advanced the view that a child can learn by observing his or her social environment and not necessarily from having been reinforced for enacting a behavior, although they did not rule out the influence of reinforcement on learning a behavior. [100]

Technological advances also renewed interest in mental states and mental representations. English neuroscientist Charles Sherrington and Canadian psychologist Donald O. Hebb used experimental methods to link psychological phenomena to the structure and function of the brain. The rise of computer science, cybernetics, and artificial intelligence underlined the value of comparing information processing in humans and machines.

A popular and representative topic in this area is cognitive bias, or irrational thought. Psychologists (and economists) have classified and described a sizeable catalogue of biases which recur frequently in human thought. The availability heuristic, for example, is the tendency to overestimate the importance of something which happens to come readily to mind. [101]

Elements of behaviorism and cognitive psychology were synthesized to form cognitive behavioral therapy, a form of psychotherapy modified from techniques developed by American psychologist Albert Ellis and American psychiatrist Aaron T. Beck.

On a broader level, cognitive science is an interdisciplinary enterprise involving cognitive psychologists, cognitive neuroscientists, linguists, and researchers in artificial intelligence, human–computer interaction, and computational neuroscience. The discipline of cognitive science covers cognitive psychology as well as philosophy of mind, computer science, and neuroscience. [102] Computer simulations are sometimes used to model phenomena of interest.


Social psychology is concerned with how behaviors, thoughts, feelings, and the social environment influence human interactions. [103] Social psychologists study such topics as the influence of others on an individual's behavior (e.g. conformity, persuasion) and the formation of beliefs, attitudes, and stereotypes about other people. Social cognition fuses elements of social and cognitive psychology for the purpose of understanding how people process, remember, or distort social information. The study of group dynamics involves research on the nature of leadership, organizational communication, and related phenomena. In recent years, many social psychologists have become increasingly interested in implicit measures, mediational models, and the interaction of person and social factors in accounting for behavior. Some concepts that sociologists have applied to the study of psychiatric disorders, concepts such as the social role, sick role, social class, life events, culture, migration, and total institution, have influenced social psychologists. [104]


Psychoanalysis refers to the theories and therapeutic techniques applied to the unconscious mind and its impact on everyday life. These theories and techniques inform treatments for mental disorders. [105] [106] [107] Psychoanalysis originated in the 1890s, most prominently with the work of Sigmund Freud. Freud's psychoanalytic theory was largely based on interpretive methods, introspection, and clinical observation. It became very well known, largely because it tackled subjects such as sexuality, repression, and the unconscious. [108] Freud pioneered the methods of free association and dream interpretation. [109] [110]

Psychoanalytic theory is not monolithic. Other well known psychoanalytic thinkers who, to a greater or lesser degree, diverged with Freud include Alfred Adler, Carl Jung, Erik Erikson, Melanie Klein, D.W. Winnicott, Karen Horney, Erich Fromm, John Bowlby, Freud's daughter Anna Freud, and Harry Stack Sullivan. These individuals ensured that psychoanalysis would evolve into diverse schools of thought. Among these schools are ego psychology, object relations, and interpersonal, Lacanian, and relational psychoanalysis.

Psychologists such as Hans Eysenck and philosophers including Karl Popper sharply criticized psychoanalysis. Popper argued that psychoanalysis had been misrepresented as a scientific discipline, [111] whereas Eysenck advanced the view that psychoanalytic tenets had been contradicted by experimental data. By the end of 20th century, psychology departments in American universities mostly marginalized Freudian theory, dismissing it as a "desiccated and dead" historical artifact. [112] Researchers such as António Damásio, Oliver Sacks, and Joseph LeDoux, and individuals in the emerging field of neuro-psychoanalysis, however, have defended some of Freud's ideas on scientific grounds. [113]

Existential-humanistic theories

Humanistic psychology, which has been influenced by existentialism and phenomenology, [115] stresses free will and self-actualization. [116] It emerged in the 1950s as a movement within academic psychology, in reaction to both behaviorism and psychoanalysis. [117] The humanistic approach seeks to view the whole person, not just fragmented parts of the personality or isolated cognitions. [118] Humanistic psychology also focuses on personal growth, self-identity, death, aloneness, and freedom. It emphasizes subjective meaning, the rejection of determinism, and concern for positive growth rather than pathology. Some founders of the humanistic school of thought were American psychologists Abraham Maslow, who formulated a hierarchy of human needs, and Carl Rogers, who created and developed client-centered therapy.

Later, positive psychology opened up humanistic themes to scientific study. Positive psychology is the study of factors which contribute to human happiness and well-being, focusing more on people who are currently healthy. In 2010, Clinical Psychological Review published a special issue devoted to positive psychological interventions, such as gratitude journaling and the physical expression of gratitude. It is, however, far from clear that positive psychology is effective in making people happier. [119] [120] Positive psychological interventions have been limited in scope, but their effects are thought to be somewhat better than placebo effects. The evidence, however, is far from clear that interventions based on positive psychology increase human happiness or resilience. [119] [120]

The American Association for Humanistic Psychology, formed in 1963, declared:

Humanistic psychology is primarily an orientation toward the whole of psychology rather than a distinct area or school. It stands for respect for the worth of persons, respect for differences of approach, open-mindedness as to acceptable methods, and interest in exploration of new aspects of human behavior. As a "third force" in contemporary psychology, it is concerned with topics having little place in existing theories and systems: e.g., love, creativity, self, growth, organism, basic need-gratification, self-actualization, higher values, being, becoming, spontaneity, play, humor, affection, naturalness, warmth, ego-transcendence, objectivity, autonomy, responsibility, meaning, fair-play, transcendental experience, peak experience, courage, and related concepts. [121]

Existential psychology emphasizes the need to understand a client's total orientation towards the world. Existential psychology is opposed to reductionism, behaviorism, and other methods that objectify the individual. [116] In the 1950s and 1960s, influenced by philosophers Søren Kierkegaard and Martin Heidegger, psychoanalytically trained American psychologist Rollo May helped to develop existential psychology. Existential psychotherapy, which follows from existential psychology, is a therapeutic approach that is based on the idea that a person's inner conflict arises from that individual's confrontation with the givens of existence. Swiss psychoanalyst Ludwig Binswanger and American psychologist George Kelly may also be said to belong to the existential school. [122] Existential psychologists tend to differ from more "humanistic" psychologists in the former's relatively neutral view of human nature and relatively positive assessment of anxiety. [123] Existential psychologists emphasized the humanistic themes of death, free will, and meaning, suggesting that meaning can be shaped by myths and narratives meaning can be deepened by the acceptance of free will, which is requisite to living an authentic life, albeit often with anxiety with regard to death. [124]

Austrian existential psychiatrist and Holocaust survivor Viktor Frankl drew evidence of meaning's therapeutic power from reflections upon his own internment. [125] He created a variation of existential psychotherapy called logotherapy, a type of existentialist analysis that focuses on a will to meaning (in one's life), as opposed to Adler's Nietzschean doctrine of will to power or Freud's will to pleasure. [126]


Personality psychology is concerned with enduring patterns of behavior, thought, and emotion. Theories of personality vary across different psychological schools of thought. Each theory carries different assumptions about such features as the role of the unconscious and the importance of childhood experience. According to Freud, personality is based on the dynamic interactions of the id, ego, and super-ego. [127] By contrast, trait theorists have developed taxonomies of personality constructs in describing personality in terms of key traits. Trait theorists have often employed statistical data-reduction methods, such as factor analysis. Although the number of proposed traits has varied widely, Hans Eysenck's early biologically-based model suggests at least three major trait constructs are necessary to describe human personality, extraversion–introversion, neuroticism-stability, and psychoticism-normality. Raymond Cattell empirically derived a theory of 16 personality factors at the primary-factor level and up to eight broader second-stratum factors. [128] [129] [130] [131] Since the 1980s, the Big Five (openness to experience, conscientiousness, extraversion, agreeableness, and neuroticism) emerged as an important trait theory of personality. [132] Dimensional models of personality are receiving increasing support, and a version of dimensional assessment has been included in the DSM-V. However, despite a plethora of research into the various versions of the "Big Five" personality dimensions, it appears necessary to move on from static conceptualizations of personality structure to a more dynamic orientation, acknowledging that personality constructs are subject to learning and change over the lifespan. [133] [134]

An early example of personality assessment was the Woodworth Personal Data Sheet, constructed during World War I. The popular, although psychometrically inadequate, Myers–Briggs Type Indicator [135] was developed to assess individuals' "personality types" according to the personality theories of Carl Jung. The Minnesota Multiphasic Personality Inventory (MMPI), despite its name, is more a dimensional measure of psychopathology than a personality measure. [136] California Psychological Inventory contains 20 personality scales (e.g., independence, tolerance). [137] The International Personality Item Pool, which is in the public domain, has become a source of scales that can be used personality assessment. [138]

Unconscious mind

Study of the unconscious mind, a part of the psyche outside the individual's awareness but that is believed to influence conscious thought and behavior, was a hallmark of early psychology. In one of the first psychology experiments conducted in the United States, C.S. Peirce and Joseph Jastrow found in 1884 that research subjects could choose the minutely heavier of two weights even if consciously uncertain of the difference. [139] Freud popularized the concept of the unconscious mind, particularly when he referred to an uncensored intrusion of unconscious thought into one's speech (a Freudian slip) or to his efforts to interpret dreams. [140] His 1901 book The Psychopathology of Everyday Life catalogues hundreds of everyday events that Freud explains in terms of unconscious influence. Pierre Janet advanced the idea of a subconscious mind, which could contain autonomous mental elements unavailable to the direct scrutiny of the subject. [141]

The concept of unconscious processes has remained important in psychology. Cognitive psychologists have used a "filter" model of attention, according to which much information processing takes place below the threshold of consciousness, and only certain stimuli, limited by their nature and number, make their way through the filter. Much research has shown that subconscious priming of certain ideas can covertly influence thoughts and behavior. [141] Because of the unreliability of self-reporting, a major hurdle in this type of research involves demonstrating that a subject's conscious mind has not perceived a target stimulus. For this reason, some psychologists prefer to distinguish between implicit and explicit memory. In another approach, one can also describe a subliminal stimulus as meeting an objective but not a subjective threshold. [142]

The automaticity model of John Bargh and others involves the ideas of automaticity and unconscious processing in our understanding of social behavior, [143] [144] although there has been dispute with regard to replication. [145] [146] Some experimental data suggest that the brain begins to consider taking actions before the mind becomes aware of them. [147] The influence of unconscious forces on people's choices bears on the philosophical question of free will. John Bargh, Daniel Wegner, and Ellen Langer describe free will as an illusion. [143] [144] [148]


Some psychologists study motivation or the subject of why people or lower animals initiate a behavior at a particular time. It also involves the study of why humans and lower animals continue or terminate a behavior. Psychologists such as William James initially used the term motivation to refer to intention, in a sense similar to the concept of will in European philosophy. With the steady rise of Darwinian and Freudian thinking, instinct also came to be seen as a primary source of motivation. [149] According to drive theory, the forces of instinct combine into a single source of energy which exerts a constant influence. Psychoanalysis, like biology, regarded these forces as demands originating in the nervous system. Psychoanalysts believed that these forces, especially the sexual instincts, could become entangled and transmuted within the psyche. Classical psychoanalysis conceives of a struggle between the pleasure principle and the reality principle, roughly corresponding to id and ego. Later, in Beyond the Pleasure Principle, Freud introduced the concept of the death drive, a compulsion towards aggression, destruction, and psychic repetition of traumatic events. [150] Meanwhile, behaviorist researchers used simple dichotomous models (pleasure/pain, reward/punishment) and well-established principles such as the idea that a thirsty creature will take pleasure in drinking. [149] [151] Clark Hull formalized the latter idea with his drive reduction model. [152]

Hunger, thirst, fear, sexual desire, and thermoregulation constitute fundamental motivations in animals. [151] Humans seem to exhibit a more complex set of motivations—though theoretically these could be explained as resulting from desires for belonging, positive self-image, self-consistency, truth, love, and control. [153] [154]

Motivation can be modulated or manipulated in many different ways. Researchers have found that eating, for example, depends not only on the organism's fundamental need for homeostasis—an important factor causing the experience of hunger—but also on circadian rhythms, food availability, food palatability, and cost. [151] Abstract motivations are also malleable, as evidenced by such phenomena as goal contagion: the adoption of goals, sometimes unconsciously, based on inferences about the goals of others. [155] Vohs and Baumeister suggest that contrary to the need-desire-fulfilment cycle of animal instincts, human motivations sometimes obey a "getting begets wanting" rule: the more you get a reward such as self-esteem, love, drugs, or money, the more you want it. They suggest that this principle can even apply to food, drink, sex, and sleep. [156]


Developmental psychology refers to the scientific study of how and why humans change over the course of their lives. [157] Given the discipline's origins in the work of Jean Piaget, developmental psychologists originally focused primarily on the development of cognition from infancy to adolescence. Later, developmental psychology extended itself to the study cognition over the life span. In addition to studying cognition, developmental psychologists have also come to focus on affective, moral, social, and neural development.

Developmental psychologists who study children use a number of research methods. For example, they make observations of children in natural settings such as preschools [158] and engage them in experimental tasks. [159] Such tasks often resemble specially designed games and activities that are both enjoyable for the child and scientifically useful. Developmental researchers have even devised clever methods to study the mental processes of infants. [160] In addition to studying children, developmental psychologists also study aging and processes throughout the life span, including old age. [161] These psychologists draw on the full range of psychological theories to inform their research. [157]

Genes and environment

All researched psychological traits are influenced by both genes and environment, to varying degrees. [162] [163] These two sources of influence are often confounded in observational research of individuals and families. An example of this confounding can be shown in the transmission of depression from a depressed mother to her offspring. A theory based on environmental transmission would hold that an offspring, by virtue of his or her having a problematic rearing environment managed by a depressed mother, is at risk for developing depression. On the other hand, a hereditarian theory would hold that depression risk in an offspring is influenced to some extent by genes passed to the child from the mother. Genes and environment in these simple transmission models are completely confounded. A depressed mother may both carry genes that contribute to depression in her offspring and also create a rearing environment that increases the risk of depression in her child.

Behavioral genetics researchers have employed methodologies that help to disentangle this confound and understand the nature and origins of individual differences in behavior. [78] Traditionally the research has involved twin studies and adoption studies, two designs where genetic and environmental influences can be partially un-confounded. More recently, gene-focused research has contributed to understanding genetic contributions to the development of psychological traits.

The availability of microarray molecular genetic or genome sequencing technologies allows researchers to measure participant DNA variation directly, and test whether individual genetic variants within genes are associated with psychological traits and psychopathology through methods including genome-wide association studies. One goal of such research is similar to that in positional cloning and its success in Huntington's: once a causal gene is discovered biological research can be conducted to understand how that gene influences the phenotype. One major result of genetic association studies is the general finding that psychological traits and psychopathology, as well as complex medical diseases, are highly polygenic, [164] [165] [166] [167] [168] where a large number (on the order of hundreds to thousands) of genetic variants, each of small effect, contribute to individual differences in the behavioral trait or propensity to the disorder. Active research continues to work toward understanding the genetic and environmental bases of behavior and their interaction.

Psychology encompasses many subfields and includes different approaches to the study of mental processes and behavior.

Psychological testing

Psychological testing has ancient origins, dating as far back as 2200 BC, in the examinations for the Chinese civil service. Written exams began during the Han dynasty (202 BC – AD 200). By 1370, the Chinese system required a stratified series of tests, involving essay writing and knowledge of diverse topics. The system was ended in 1906. [169] In Europe, mental assessment took a different approach, with theories of physiognomy—judgment of character based on the face—described by Aristotle in 4th century BC Greece. Physiognomy remained current through the Enlightenment, and added the doctrine of phrenology: a study of mind and intelligence based on simple assessment of neuroanatomy. [170]

When experimental psychology came to Britain, Francis Galton was a leading practitioner. By virtue of his procedures for measuring reaction time and sensation, he is considered an inventor of modern mental testing (also known as psychometrics). [171] James McKeen Cattell, a student of Wundt and Galton, brought the idea of psychological testing to the United States, and in fact coined the term "mental test". [172] In 1901, Cattell's student Clark Wissler published discouraging results, suggesting that mental testing of Columbia and Barnard students failed to predict academic performance. [172] In response to 1904 orders from the Minister of Public Instruction, French psychologists Alfred Binet and Théodore Simon developed and elaborated a new test of intelligence in 1905–1911. They used a range of questions diverse in their nature and difficulty. Binet and Simon introduced the concept of mental age and referred to the lowest scorers on their test as idiots. Henry H. Goddard put the Binet-Simon scale to work and introduced classifications of mental level such as imbecile and feebleminded. In 1916 (after Binet's death), Stanford professor Lewis M. Terman modified the Binet-Simon scale (renamed the Stanford–Binet scale) and introduced the intelligence quotient as a score report. [173] Based on his test findings, and reflecting the racism common to that era, Terman concluded that mental retardation "represents the level of intelligence which is very, very common among Spanish-Indians and Mexican families of the Southwest and also among negroes. Their dullness seems to be racial." [174]

Following the Army Alpha and Army Beta tests for soldiers in World War I, mental testing became popular in the US, where it was soon applied to schoolchildren. The federally created National Intelligence Test was administered to 7 million children in the 1920s. In 1926, the College Entrance Examination Board created the Scholastic Aptitude Test to standardize college admissions. [175] The results of intelligence tests were used to argue for segregated schools and economic functions, including the preferential training of Black Americans for manual labor. These practices were criticized by Black intellectuals such a Horace Mann Bond and Allison Davis. [174] Eugenicists used mental testing to justify and organize compulsory sterilization of individuals classified as mentally retarded. [44] In the United States, tens of thousands of men and women were sterilized. Setting a precedent that has never been overturned, the U.S. Supreme Court affirmed the constitutionality of this practice in the 1927 case Buck v. Bell. [176]

Today mental testing is a routine phenomenon for people of all ages in Western societies. [177] Modern testing aspires to criteria including standardization of procedure, consistency of results, output of an interpretable score, statistical norms describing population outcomes, and, ideally, effective prediction of behavior and life outcomes outside of testing situations. [178] Developments in psychometrics include work on test and scale reliability and validity. [179] Developments in item-response theory, [180] structural equation modeling, [181] and bifactor analysis [182] have helped in strengthening test and scale construction.

Mental health care

The provision of psychological health services is generally called clinical psychology in the U.S. Sometimes, however, members of the school psychology and counseling psychology professions engage in practices that resemble that of clinical psychologists. Clinical psychologists typically include people who have graduated from doctoral programs in clinical psychology. In Canada, some of the members of the abovementioned groups usually fall within the larger category of professional psychology. In Canada and the U.S., practitioners get bachelor's degrees and doctorates doctoral students in clinical psychology usually spend one year in a predoctoral internship and one year in postdoctoral internship. In Mexico and most other Latin American and European countries, psychologists do not get bachelor's and doctoral degrees instead, they take a three-year professional course following high school. [66] Clinical psychology is at present the largest specialization within psychology. [183] It includes the study and application of psychology for the purpose of understanding, preventing, and relieving psychological distress, dysfunction, and/or mental illness. Clinical psychologists also try to promote subjective well-being and personal growth. Central to the practice of clinical psychology are psychological assessment and psychotherapy although clinical psychologists may also engage in research, teaching, consultation, forensic testimony, and program development and administration. [184]

Credit for the first psychology clinic in the United States typically goes to Lightner Witmer, who established his practice in Philadelphia in 1896. Another modern psychotherapist was Morton Prince, an early advocate for the establishment of psychology as a clinical and academic discipline. [183] In the first part of the twentieth century, most mental health care in the United States was performed by psychiatrists, who are medical doctors. Psychology entered the field with its refinements of mental testing, which promised to improve the diagnosis of mental problems. For their part, some psychiatrists became interested in using psychoanalysis and other forms of psychodynamic psychotherapy to understand and treat the mentally ill. [39] [185]

Psychotherapy as conducted by psychiatrists blurred the distinction between psychiatry and psychology, and this trend continued with the rise of community mental health facilities. Some in the clinical psychology community adopted behavioral therapy, a thoroughly non-psychodynamic model that used behaviorist learning theory to change the actions of patients. A key aspect of behavior therapy is empirical evaluation of the treatment's effectiveness. In the 1970s, cognitive-behavior therapy emerged with the work of Albert Ellis and Aaron Beck. Although there are similarities between behavior therapy and cognitive-behavior therapy, cognitive-behavior therapy required the application of cognitive constructs. Since the 1970s, the popularity of cognitive-behavior therapy among clinical psychologists increased. A key practice in behavioral and cognitive-behavioral therapy is exposing patients to things they fear, based on the premise that their responses (fear, panic, anxiety) can be deconditioned. [186]

Mental health care today involves psychologists and social workers in increasing numbers. In 1977, National Institute of Mental Health director Bertram Brown described this shift as a source of "intense competition and role confusion." [39] Graduate programs issuing doctorates in clinical psychology emerged in the 1950s and underwent rapid increase through the 1980s. The PhD degree is intended to train practitioners who could also conduct scientific research. The PsyD degree is more exclusively designed to train practitioners. [66]

Some clinical psychologists focus on the clinical management of patients with brain injury. This subspecialty is known as clinical neuropsychology. In many countries, clinical psychology is a regulated mental health profession. The emerging field of disaster psychology (see crisis intervention) involves professionals who respond to large-scale traumatic events. [187]

The work performed by clinical psychologists tends to be influenced by various therapeutic approaches, all of which involve a formal relationship between professional and client (usually an individual, couple, family, or small group). Typically, these approaches encourage new ways of thinking, feeling, or behaving. Four major theoretical perspectives are psychodynamic, cognitive behavioral, existential–humanistic, and systems or family therapy. There has been a growing movement to integrate the various therapeutic approaches, especially with an increased understanding of issues regarding culture, gender, spirituality, and sexual orientation. With the advent of more robust research findings regarding psychotherapy, there is evidence that most of the major therapies have equal effectiveness, with the key common element being a strong therapeutic alliance. [188] [189] Because of this, more training programs and psychologists are now adopting an eclectic therapeutic orientation. [190] [191] [192] [193] [194]

Diagnosis in clinical psychology usually follows the Diagnostic and Statistical Manual of Mental Disorders (DSM). [195] The study of mental illnesses is called abnormal psychology.


Educational psychology is the study of how humans learn in educational settings, the effectiveness of educational interventions, the psychology of teaching, and the social psychology of schools as organizations. The work of developmental psychologists such as Lev Vygotsky, Jean Piaget, and Jerome Bruner has been influential in creating teaching methods and educational practices. Educational psychology is often included in teacher education programs in places such as North America, Australia, and New Zealand.

School psychology combines principles from educational psychology and clinical psychology to understand and treat students with learning disabilities to foster the intellectual growth of gifted students to facilitate prosocial behaviors in adolescents and otherwise to promote safe, supportive, and effective learning environments. School psychologists are trained in educational and behavioral assessment, intervention, prevention, and consultation, and many have extensive training in research. [196]

Industrial and organizational (I/O) psychology involves research and practices that apply psychological theories and principles to organizations and individuals' work-lives. [197] In the field's beginnings, industrialists brought the nascent field of psychology to bear on the study of scientific management techniques for improving workplace efficiency. The field was at first called economic psychology or business psychology later, industrial psychology, employment psychology, or psychotechnology. [198] An influential early study examined workers at Western Electric's Hawthorne plant in Cicero, Illinois from 1924–1932. Western Electric experimented on factory workers to assess their responses to changes in illumination, breaks, food, and wages. The researchers came to focus on workers' responses to observation itself, and the term Hawthorne effect is now used to describe the fact that people work harder when they think they're being watched. [199] Although the Hawthorne research can be found in psychology textbooks, the research and its findings, however, were weak at best. [200] [201]

The name industrial and organizational psychology emerged in the 1960s. In 1973, it became enshrined in the name of the Society for Industrial and Organizational Psychology, Division 14 of the American Psychological Association. [198] One goal of the discipline is to optimize human potential in the workplace. Personnel psychology is a subfield of I/O psychology. Personnel psychologists apply the methods and principles of psychology in selecting and evaluating workers. Another subfield, organizational psychology, examines the effects of work environments and management styles on worker motivation, job satisfaction, and productivity. [202] Most I/O psychologists work outside of academia, for private and public organizations and as consultants. [198] A psychology consultant working in business today might expect to provide executives with information and ideas about their industry, their target markets, and the organization of their company. [203] [204]

Organizational behavior (OB) is an allied field involved in the study of human behavior within organizations. [205] One way to differentiate I/O psychology from OB is to note that I/O psychologists train in university psychology departments and OB specialists, in business schools.

Military and intelligence

One role for psychologists in the military has been to evaluate and counsel soldiers and other personnel. In the U.S., this function began during World War I, when Robert Yerkes established the School of Military Psychology at Fort Oglethorpe in Georgia. The school provided psychological training for military staff. [39] [206] Today, U.S Army psychologists perform psychological screening, clinical psychotherapy, suicide prevention, and treatment for post-traumatic stress, as well as provide prevention-related services, for example, smoking cessation. [207]

Psychologists may also work on a diverse set of campaigns known broadly as psychological warfare. Psychological warfare chiefly involves the use of propaganda to influence enemy soldiers and civilians. This so-called black propaganda is designed to seem as if it originates from a source other than the Army. [208] The CIA's MKULTRA program involved more individualized efforts at mind control, involving techniques such as hypnosis, torture, and covert involuntary administration of LSD. [209] The U.S. military used the name Psychological Operations (PSYOP) until 2010, when these activities were reclassified as Military Information Support Operations (MISO), part of Information Operations (IO). [210] Psychologists have sometimes been involved in assisting the interrogation and torture of suspects, staining the records of the psychologists involved. [211]

Health, well-being, and social change

Medical facilities increasingly employ psychologists to perform various roles. A prominent aspect of health psychology is the psychoeducation of patients: instructing them in how to follow a medical regimen. Health psychologists can also educate doctors and conduct research on patient compliance. [212] [213] Psychologists in the field of public health use a wide variety of interventions to influence human behavior. These range from public relations campaigns and outreach to governmental laws and policies. Psychologists study the composite influence of all these different tools in an effort to influence whole populations of people. [214]

An outstanding example of the contribution of psychologists to social change involves the research of Kenneth and Mamie Clark. These two African American psychologists studied segregation's the adverse psychological impact on children. Their research findings played a role in the desegregation case Brown v. Board of Education (1954). [215]

Occupational health psychology (OHP) is a branch of psychology that is very much interdisciplinary. It is concerned with the health and safety of workers. [47] [216] OHP addresses topic areas such as the impact of occupational stressors on physical and mental health, workplace mistreatment, work-family balance, the impact of involuntary unemployment on physical and mental health, safety/accidents, and interventions designed to improve/protect worker health. [47] [217] OHP grew out of health psychology and I/O psychology. [218] OHP has also been informed by disciplines outside psychology, including occupational medicine, industrial engineering, and economics. [219] [220]

Quantitative psychological research lends itself to the statistical testing of hypotheses. Although the field makes abundant use of randomized and controlled experiments in laboratory settings, such research can only assess a limited range of short-term phenomena. Some psychologists rely on less rigorously controlled, but more ecologically valid, field experiments as well. Other research psychologists rely on statistical methods to glean knowledge from population data. [221] The statistical methods research psychologists employ include the Pearson product–moment correlation coefficient, the analysis of variance, multiple linear regression, logistic regression, structural equation modeling, and hierarchical linear modeling. The measurement and operationalization of important constructs is an essential part of these research designs.

Although this type of psychological research is much less abundant than quantitative research, some psychologists conduct qualitative research. This type of research can involve interviews, questionnaires, and first-hand observation. [222] While hypothesis testing is rare, virtually impossible, in qualitative research, qualitative studies can be helpful in theory and hypothesis generation, interpreting seemingly contradictory quantitative findings, and understanding why some interventions fail and others succeed. [223]

Controlled experiments

A true experiment with random assignment of research participants (sometimes called subjects) to rival conditions allows researchers to make strong inferences about causal relationships. When there are large numbers of research participants, the random assignment (also called random allocation) of those participants to rival conditions ensures that the individuals in those conditions will, on average, be similar on most characteristics, including characteristics that went unmeasured. In an experiment, the researcher alters one or more variables of influence, called independent variables, and measures resulting changes in the factors of interest, called dependent variables. Prototypical experimental research is conducted in a laboratory with a carefully controlled environment.

A quasi-experiment refers to a situation in which there are rival conditions under study but random assignment to the different conditions is not possible. Investigators must work with preexisting groups of people. Researchers can use common sense to consider how much the nonrandom assignment threatens the study's validity. [226] For example, in research on the best way to affect reading achievement in the first three grades of school, school administrators may not permit educational psychologists to randomly assign children to phonics and whole language classrooms, in which case the psychologists must work with preexisting classroom assignments. Psychologists will compare the achievement of children attending phonics and whole language classes and, perhaps, statistically adjust for any initial differences in reading level.

Experimental researchers typically use a statistical hypothesis testing model which involves making predictions before conducting the experiment, then assessing how well the data collected are consistent with the predictions. These predictions are likely to originate from one or more abstract scientific hypotheses about how the phenomenon under study actually works. [227]

Other types of studies

Surveys are used in psychology for the purpose of measuring attitudes and traits, monitoring changes in mood, and checking the validity of experimental manipulations (checking research participants' perception of the condition they were assigned to). Psychologists have commonly used paper-and-pencil surveys. However, surveys are also conducted over the phone or through e-mail. Web-based surveys are increasingly used to conveniently reach many subjects.

Observational studies are commonly conducted in psychology. In cross-sectional observational studies, psychologists collect data at a single point in time. The goal of many cross-sectional studies is the assess the extent factors are correlated with each other. By contrast, in longitudinal studies psychologists collect data on the same sample at two or more points in time. Sometimes the purpose of longitudinal research is to study trends across time such as the stability of traits or age-related changes in behavior. Because some studies involve endpoints that psychologists cannot ethically study from an experimental standpoint, such as identifying the causes of depression, they conduct longitudinal studies a large group of depression-free people, periodically assessing what is happening in the individuals' lives. In this way psychologists have an opportunity to test causal hypotheses regarding conditions that commonly arise in people's lives that put them at risk for depression. Problems that affect longitudinal studies include selective attrition, the type of problem in which bias is introduced when a certain type of research participant disproportionately leaves a study.

Exploratory data analysis refers to a variety of practices that researchers use to reduce a great many variables to a small number overarching factors. In Peirce's three modes of inference, exploratory data analysis corresponds to abduction. [228] Meta-analysis is the technique research psychologists use to integrate results from many studies of the same variables and arriving at a grand average of the findings. [229]

Technological assays

A classic and popular tool used to relate mental and neural activity is the electroencephalogram (EEG), a technique using amplified electrodes on a person's scalp to measure voltage changes in different parts of the brain. Hans Berger, the first researcher to use EEG on an unopened skull, quickly found that brains exhibit signature "brain waves": electric oscillations which correspond to different states of consciousness. Researchers subsequently refined statistical methods for synthesizing the electrode data, and identified unique brain wave patterns such as the delta wave observed during non-REM sleep. [230]

Newer functional neuroimaging techniques include functional magnetic resonance imaging and positron emission tomography, both of which track the flow of blood through the brain. These technologies provide more localized information about activity in the brain and create representations of the brain with widespread appeal. They also provide insight which avoids the classic problems of subjective self-reporting. It remains challenging to draw hard conclusions about where in the brain specific thoughts originate—or even how usefully such localization corresponds with reality. However, neuroimaging has delivered unmistakable results showing the existence of correlations between mind and brain. Some of these draw on a systemic neural network model rather than a localized function model. [231] [232] [233]

Psychiatric interventions such as transcranial magnetic stimulation and drugs also provide information about brain–mind interactions. Psychopharmacology is the study of drug-induced mental effects.

Computer simulation

Computational modeling is a tool used in mathematical psychology and cognitive psychology to simulate behavior. [234] This method has several advantages. Since modern computers process information quickly, simulations can be run in a short time, allowing for high statistical power. Modeling also allows psychologists to visualize hypotheses about the functional organization of mental events that couldn't be directly observed in a human. Computational neuroscience uses mathematical models to simulate the brain. Another method is symbolic modeling, which represents many mental objects using variables and rules. Other types of modeling include dynamic systems and stochastic modeling.

Animal studies

Animal experiments aid in investigating many aspects of human psychology, including perception, emotion, learning, memory, and thought, to name a few. In the 1890s, Russian physiologist Ivan Pavlov famously used dogs to demonstrate classical conditioning. Non-human primates, cats, dogs, pigeons, and rats and other rodents are often used in psychological experiments. Ideally, controlled experiments introduce only one independent variable at a time, in order to ascertain its unique effects upon dependent variables. These conditions are approximated best in laboratory settings. In contrast, human environments and genetic backgrounds vary so widely, and depend upon so many factors, that it is difficult to control important variables for human subjects. There are pitfalls, however, in generalizing findings from animal studies to humans through animal models. [235]

Comparative psychology refers to the scientific study of the behavior and mental processes of non-human animals, especially as these relate to the phylogenetic history, adaptive significance, and development of behavior. Research in this area explores the behavior of many species, from insects to primates. It is closely related to other disciplines that study animal behavior such as ethology. [236] Research in comparative psychology sometimes appears to shed light on human behavior, but some attempts to connect the two have been quite controversial, for example the Sociobiology of E.O. Wilson. [237] Animal models are often used to study neural processes related to human behavior, e.g. in cognitive neuroscience.

Qualitative research

Qualitative research is often designed to answer questions about the thoughts, feelings, and behaviors of individuals. Qualitative research involving first-hand observation can help describe events as they occur, with the goal of capturing the richness of everyday behavior and with the hope of discovering and understanding phenomena that might have been missed if only more cursory examinations have been made.

Qualitative psychological research methods include interviews, first-hand observation, and participant observation. Creswell (2003) identifies five main possibilities for qualitative research, including narrative, phenomenology, ethnography, case study, and grounded theory. Qualitative researchers [238] sometimes aim to enrich interpretations or critiques of symbols, subjective experiences, or social structures. Sometimes hermeneutic and critical aims can give rise to quantitative research, as in Erich Fromm's application of psychological and sociological theories, in his book Escape from Freedom, to understanding why many ordinary Germans supported Hitler. [239]

Just as Jane Goodall studied chimpanzee social and family life by careful observation of chimpanzee behavior in the field, psychologists conduct naturalistic observation of ongoing human social, professional, and family life. Sometimes the participants are aware they are being observed, and other times the participants do not know they are being observed. Strict ethical guidelines must be followed when covert observation is being carried out.

Program Evaluation

Program Evaluation is a systematic method for collecting, analyzing, and using information to answer questions about projects, policies and programs, particularly about their effectiveness. [241] [242] In both the public and private sectors, stakeholders often want to know whether the programs they are funding, implementing, voting for, receiving, or objecting to are producing their intended effect. While program evaluation first focuses on effectiveness, important considerations often include how much the program costs per participant, how the program could be improved, whether the program is worthwhile, whether there are better alternatives, if there are unintended outcomes, and whether the program goals are appropriate and useful. [243]


The field of metascience has revealed problems in psychological research. Some psychological research has suffered from bias, [244] problematic reproducibility, [245] and misuse of statistics. [246] These findings have led to calls for reform from within and from outside the scientific community. [247]

Confirmation bias

In 1959, statistician Theodore Sterling examined the results of psychological studies and discovered that 97% of them supported their initial hypotheses, implying a possible publication bias. [248] [249] [250] Similarly, Fanelli (2010) [251] found that 91.5% of psychiatry/psychology studies confirmed the effects they were looking for, and concluded that the odds of this happening (a positive result) was around five times higher than in fields such as space- or geosciences. Fanelli argues that this is because researchers in "softer" sciences have fewer constraints to their conscious and unconscious biases.


A replication crisis in psychology has emerged. Many notable findings in the field have not been replicated. Some researchers were even accused of publishing fraudulent results. [252] [253] [254] Systematic efforts, including efforts by the Reproducibility Project of the Center for Open Science, to assess the extent of the problem found that as many as two-thirds of highly publicized findings in psychology failed to be replicated. [255] Reproducibility has generally been stronger in cognitive psychology (in studies and journals) than social psychology [255] and subfields of differential psychology. [256] [257] Other subfields of psychology have also been implicated in the replication crisis, including clinical psychology, [258] [259] developmental psychology, [260] [261] [262] and a field closely related to psychology, educational research. [263] [264] [265] [266]

Focus on the replication crisis has led to other renewed efforts in the discipline to re-test important findings. [267] [268] In response to concerns about publication bias and data dredging (conducting a large number of statistical tests on a great many variables but restricting reporting to the results that were statistically significant), 295 psychology and medical journals have adopted result-blind peer review where studies are accepted not on the basis of their findings and after the studies are completed, but before the studies are conducted and upon the basis of the methodological rigor of their experimental designs and the theoretical justifications for their proposed statistical analysis before data collection or analysis is conducted. [269] [270] In addition, large-scale collaborations among researchers working in multiple labs in different countries have taken place. The collaborators regularly make their data openly available for different researchers to assess. [271] Allen et al. [272] estimated that 61 percent of result-blind studies have yielded null results, in contrast to an estimated 5 to 20 percent in traditional research.

Misuse of statistics

Some critics view statistical hypothesis testing as misplaced. Psychologist and statistician Jacob Cohen wrote in 1994 that psychologists routinely confuse statistical significance with practical importance, enthusiastically reporting great certainty in unimportant facts. [273] Some psychologists have responded with an increased use of effect size statistics, rather than sole reliance on p-values. [274]

WEIRD bias

In 2008, Arnett pointed out that most articles in American Psychological Association journals were about U.S. populations when U.S. citizens are only 5% of the world's population. He complained that psychologists had no basis for assuming psychological processes to be universal and generalizing research findings to the rest of the global population. [275] In 2010, Henrich, Heine, and Norenzayan reported a bias in conducting psychology studies with participants from "WEIRD" ("Western, Educated, Industrialized, Rich, and Democratic") societies. [276] [277] Henrich et al. found that "96% of psychological samples come from countries with only 12% of the world’s population" (p. 63). The article gave examples of results that differ significantly between people from WEIRD and tribal cultures, including the Müller-Lyer illusion. Arnett (2008), Altmaier, and Hall (2008) and Morgan-Consoli et al. (2018) view the Western bias in research and theory as a serious problem considering psychologists are increasingly applying psychological principles developed in WEIRD regions in their research, clinical work, and consultation with populations around the world. [275] [278] [279] In 2018, Rad, Martingano, and Ginges showed that nearly a decade after Henrich et al.'s paper, over 80% of the samples used in studies published in the journal Psychological Science employed WEIRD samples. Moreover, their analysis showed that several studies did not fully disclose the origin of their samples the authors offered a set of recommendations to editors and reviewers to reduce WEIRD bias. [280]

Unscientific mental health training

Some observers perceive a gap between scientific theory and its application—in particular, the application of unsupported or unsound clinical practices. [281] Critics say there has been an increase in the number of mental health training programs that do not instill scientific competence. [282] Practices such as "facilitated communication for infantile autism" memory-recovery techniques including body work and other therapies, such as rebirthing and reparenting, may be dubious or even dangerous, despite their popularity. [283] These practices, however, are outside the mainstream practices taught in clinical psychology doctoral programs.

Ethical standards in the discipline have changed over time. Some famous past studies are today considered unethical and in violation of established codes (the Canadian Code of Conduct for Research Involving Humans, and the Belmont Report). The American Psychological Association has advanced a set of ethical principles and a code of conduct for the profession. [284]

The most important contemporary standards include informed and voluntary consent. After World War II, the Nuremberg Code was established because of Nazi abuses of experimental subjects. Later, most countries (and scientific journals) adopted the Declaration of Helsinki. In the U.S., the National Institutes of Health established the Institutional Review Board in 1966, and in 1974 adopted the National Research Act (HR 7724). All of these measures encouraged researchers to obtain informed consent from human participants in experimental studies. A number of influential but ethically dubious studies led to the establishment of this rule such studies included the MIT-Harvard Fernald School radioisotope studies, the Thalidomide tragedy, the Willowbrook hepatitis study, and Stanley Milgram's studies of obedience to authority.


Universities have ethics committees dedicated to protecting the rights (e.g., voluntary nature of the research, privacy) and well-being (e.g., minimizing distress) of research participants. University ethics committees evaluate proposed research to ensure that researchers protect the rights and well-being of participants an investigator's research project cannot be conducted unless approved by such an ethics committee. [285]

The ethics code of the American Psychological Association originated in 1951 as "Ethical Standards of Psychologists". This code has guided the formation of licensing laws in most American states. It has changed multiple times over the decades since its adoption. In 1989, the APA revised its policies on advertising and referral fees to negotiate the end of an investigation by the Federal Trade Commission. The 1992 incarnation was the first to distinguish between "aspirational" ethical standards and "enforceable" ones. Members of the public have a five-year window to file ethics complaints about APA members with the APA ethics committee members of the APA have a three-year window. [286]

Some of the ethical issues considered most important are the requirement to practice only within the area of competence, to maintain confidentiality with the patients, and to avoid sexual relations with them. Another important principle is informed consent, the idea that a patient or research subject must understand and freely choose a procedure they are undergoing. [286] Some of the most common complaints against clinical psychologists include sexual misconduct. [286]

Other animals

Research on other animals is also governed by university ethics committees. Research on nonhuman animals cannot proceed without permission of the ethics committee of the researcher's home institution. Current ethical guidelines state that using non-human animals for scientific purposes is only acceptable when the harm (physical or psychological) done to animals is outweighed by the benefits of the research. [287] Keeping this in mind, psychologists can use certain research techniques on animals that could not be used on humans.

5 Famous Psychologists in History

Like any profession, psychology has evolved since its inception. It has been shaped by some of the greatest thinkers and scientists of the human mind. Their work has influenced society’s ability to understand why people are the way they are, why they do the things that they do and how their behaviors can be changed. Five famous psychologists in history stand out above the rest for their contributions to this field.

1. Sigmund Freud – Freud is perhaps the most well-known psychologist in history. He explored the personality and human psyche as it relates to the id, the ego and the superego. A phrase named after him is the Freudian slip. It refers to the subconscious substitution of one word for another that people sometimes make while they are talking to others.

2. B.F. Skinner – The study of behavior modification and reinforcement significantly influenced how people are treated in society today. He received several awards over his lifetime. These honors included the National Medal of Science in 1968, the Human of the Year Award in 1972 and a Citation for Outstanding Lifetime Contribution to Psychology in 1990.

3. Albert Bandura – Bandura’s groundbreaking theories on personalities and therapy put him on the short list of famous psychologists in history. His approach is more oriented to action than that of others who came before him in this field. A native of Canada, the specialist in social cognitive theory has worked in the field of psychology in the U.S. for many years and is still active today. His work in a person’s ability to exercise control over their actions has been at the root of several 12-step programs.

4. Carl Jung – Jung was influenced by Freud in his work, although he disagreed with some of those theories. Jung’s contributions to psychology involved new ideas about the human psyche and the collective unconscious.

5. Mary Ainsworth – Ainsworth provided great insight into child behavior as it relates to development. She delved into the field of attachment theory and broke ground with her Strange Situation Assessment study on toddlers and their relationships with their parents.

Some of the greatest minds in psychology are quite famous. Their theories have led to breakthroughs in helping everyday people to cope with their lives and the world around them, but a psychologist doesn’t have to be famous to make a difference. If you’re in New York and you need clarity from a professional, Comprehensive Consultation Psychological Service can help. A psychologist in NYC can analyze the issues at hand regarding personal situations or business-related scenarios. Contact our office to find out how.

List of Influential Psychologists and Therapists

Psychologists and psychotherapists impact our lives, shape the way we think, and act as experienced guides as we journey into uncharted territories. They provide invaluable insights into the world of healing, innovative developments for growth, and paths toward empowerment. We have chosen to highlight some of the most influential psychologists, psychiatrists, therapists, and thinkers in history, giving a brief biography of their beginnings and their contributions to their profession.

Psychology began formally in 1879 with Wilhelm Wundt and the foundation of a laboratory for experimental study in Leipzig, Germany. But for centuries before, the ancient Greeks, Egyptians, Indians, and Muslims practiced various forms of psychotherapy, attempting even then to explore the many facets of the mind. G. Stanley Hall was one of the first philosophers to introduce America to applied psychology, and it quickly spread to fields of law, industry, and business. At the same time, in Vienna, Sigmund Freud was beginning to gain recognition for his theories, which grew into modern day psychoanalysis.

Throughout the next century, multiple disciplines of psychology emerged, including behaviorism, neurobiology, linguistics, philosophy, and meditation. The most prominent and widely accepted form of psychology that was born during that time was cognitive science, resulting in numerous therapeutic techniques that are still employed today.

The majority of the psychologists represented on the following pages are men, as they were afforded more opportunities for education than women during the infancy of this field. In the last hundred years, however, women have been responsible for pioneering many of the advancements in psychology and their contributions are an integral part of the ever growing field of mental health. From Jung to Maslow, Adler to Ainsworth, many of the practitioners on these pages have long since left this world, but their work lives on. Others are still creating change today, offering their expertise and theories through education, clinical practice, and training.


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