The Nineteenth Century
Psychology was established as an empirical, accepted science in the nineteenth century. While the measures would change, the model of research and evaluation would begin to take shape over the next 100 years.
G. Stanley Hall becomes the first American to receive a Ph.D. in psychology in 1878.
Wilhelm Wundt establishes the first experimental psychology lab dedicated to the study of the mind in Leipzig, Germany in 1879.
G. Stanley Hall establishes the first experimental psychology lab in the United States at Johns Hopkins University in 1883.
Herman Ebbinghaus publishes his seminal "Über das Gedächtnis" ("On Memory") in 1885, in which he describes his own learning and memory experiments.
In Vienna, Austria, Sigmund Freud begins offering therapy to patients in 1886.
James McKeen Cattell is appointed as the first professor of psychology at the University of Pennsylvania in 1888. He would later publish "Mental Tests and Measurements," which marked the beginning of psychological testing.
William James publishes "Principles of Psychology" in 1890. Sir Francis Galton develops correlation techniques in intelligence studies to better understand the relationship between variables.
G. Stanley Hall establishes the American Psychological Association (APA) in 1892, with 26 members in the first meeting.
Lightner Witmer opens the first psychology clinic in America in 1896.
Edward Thorndike develops the Law of Effect in 1898.
Twentieth Century
1900 to 1950
Two major figures dominated the first half of the twentieth century: Sigmund Freud and Carl Jung. These two theorists laid the groundwork for analysis during this period in modern psychology's history, including Freud's examination of psychopathology and Jung's analytic psychology.
Sigmund Freud's seminal book "Interpretation of Dreams" is published in 1900.
The British Psychological Society is founded in 1901.
Mary Whiton Calkins becomes the American Psychological Association's first female president in 1905. The intelligence test is introduced by Alfred Binet.
Ivan Pavlov publishes his findings on classical conditioning in 1906. "The Psychology of Dementia Praecox" by Carl Jung is published.
Thorndike publishes "Animal Intelligence" in 1911, which leads to the development of the operant conditioning theory.
Max Wertheimer publishes "Experimental Studies of the Perception of Movement" in 1912, paving the way for the development of Gestalt psychology.
Carl Jung begins to depart from Freudian views and develop his own theories, dubbed analytical psychology, in 1913. J.B. Watson introduces the concept of behaviourism.
Freud's work on repression is published in 1915.
Watson and Rosalie Rayner publish their research on classical conditioning of fear, focusing on the subject of their experiment, Little Albert, in 1920.
With the publication of "The Moral Judgment of the Child" in 1932, Jean Piaget establishes himself as the leading cognitive theorist.
Carl Rogers develops client-centered therapy, which promotes respect and positive regard for patients, in 1942.
1950 to 2000
The latter half of the twentieth century was devoted to standardising diagnostic criteria for mental illness. The publication of the American Psychological Association's Diagnostic and Statistical Manual of Mental Disorders was a watershed moment in this process (DSM). This fundamental tool is still used in modern psychology to guide diagnosis and treatment.
The first edition of the "Diagnostic and Statistical Manual of Mental Disorders" is published in 1952.
Maslow publishes "Motivation and Personality" in 1954, describing his theory of a hierarchy of needs. Maslow is regarded as one of the fathers of humanistic psychology.
Harry Harlow publishes "The Nature of Love" in 1958, which discusses the significance of attachment and love in rhesus monkeys.
Albert Bandura conducts his now-famous Bobo doll experiment in 1961, in which he describes child behaviour as a construct of observation, imitation, and modelling.
Bandura introduces the concept of observational learning to explain aggression in 1963.
The DSM-II is published in 1968.
Stanley Milgram publishes "Obedience to Authority" in 1974, detailing the results of his famous obedience experiments.
The DSM-III is published in 1980.
Noam Chomsky's "On the Nature, Use, and Acquisition of Language" is published in 1990.
Steven Pinker publishes an article in 1991 that introduces his theories about how children acquire language, which he later expands on in his book "The Language Instinct."
The DSM-IV is published in 1994.
The twenty-first century
With the advent of genetic science, psychologists began debating how physiology and genetics contribute to a person's psychological well-being in the twenty-first century.
Steven Pinker publishes "The Blank Slate" in 2002, arguing against the concept of a blank slate (the theory that the mind is a blank slate at birth).
Daniel Kahneman has been awarded the Nobel Memorial Prize in Economics for his work on how people make decisions in the face of uncertainty.
2003: Human gene mapping is completed, with the goal of isolating the individual chromosomes responsible for physiological and neurological conditions.
Simon LeVay publishes "Gay, Straight, and the Reason Why" in 2010, arguing that sexual orientation emerges from prenatal brain differentiation.
The DSM-5 is published in 2013. The APA, among other things, replaces "gender identity disorder" with "gender dysphoria" to describe a person's discomfort with their assigned gender.
2014: John O'Keefe, May-Britt Moser, and Edvard Moser share the Nobel Prize for discovering cells in the brain that form a positioning system.