Follow the ideas, studies, and people that shaped psychology. Explore a period or follow a topic from your course.
Compare milestones
Choose two to four milestones with the Compare boxes below. Dates are publication years, studies, or institutional events, so gaps between them are approximate.
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It is an early surviving argument that mental life has a bodily basis that can be studied without appeal to the divine.
In your course
The biological bases of behavior and the mind-body question.
Important context
The work belongs to the Hippocratic Corpus, a collection by several authors, so the author and date are uncertain. "c. 400 BCE" is a convention. The essay is medical philosophy, not experimental evidence.
It treats sensation, memory, and reasoning as natural subjects of inquiry, a template that later scholars argued with for centuries.
In your course
Origins of questions about perception, learning, and the relation of mind to body.
Important context
The date is approximate and the text circulated in copies and translations. It is philosophy and natural observation, not experiment, and modern readers disagree about how to interpret key terms.
It framed the empiricist side of debates about how much of the mind is learned.
In your course
The nature and nurture question and associationist ideas about learning.
Important context
A philosophical argument, not an experiment. The year depends on whether the first printing or its title page is cited. Some sources give 1689; the title page of the edition on Project Gutenberg reads 1690.
It showed that experience could be tied to measurable stimuli, which made sensation a topic for laboratory work.
In your course
Thresholds, sensation, and the start of quantitative methods in psychology.
Important context
The entry marks the measurement program. Fechner also held broader philosophical views about mind and body that are a separate matter from his methods.
Questions about the mind become questions researchers can test with controlled methods.
In your course
Experiments, introspection, and the origins of scientific psychology.
Important context
The Noba history calls 1879 a popular date for the science's beginning rather than a precise founding, and it credits Wundt by convention. Other early laboratories and research programs existed.
He showed that memory could be studied with controlled procedures and repeated measurement.
In your course
Learning curves, retention over time, and the logic of memory experiments.
Important context
This is the 1885 German publication; the English translation by Ruger and Bussenius appeared in 1913. Lists of syllables were an artificial task, so the results do not cover everyday memory.
Professional societies give a field shared standards, meetings, and journals.
In your course
How psychology became a profession, and later how it wrote ethics codes.
Important context
A U.S. milestone, not a global one. Fernberger names seven men at the July 8 meeting and 31 elected members; later accounts give other figures for who attended.
Women were barred from degrees at many universities, and her career shows how access shaped who did research.
In your course
Comparative psychology, and who was able to take part in early psychology.
Important context
The "first" claim is the APA's wording. In the same year Harvard refused to grant Mary Whiton Calkins a degree although she had completed her doctoral work.
It offered a measurable account of learning from consequences that led to the law of effect.
In your course
Trial-and-error learning and the road to operant conditioning.
Important context
The 1898 monograph is the original. The chapter linked here is from the 1911 expanded book, so the text and the date differ. Animal results do not automatically transfer to people.
It started standardized ability testing and the debates about what such tests can and cannot show.
In your course
Intelligence testing, norms, validity, and the misuse of scores.
Important context
The scale is usually credited to Binet and Théodore Simon; the translation linked here lists Binet as author. Binet limited the method to a child's present level, not a fixed measure of innate ability.
Psychoanalytic ideas about unconscious motives entered American psychology and popular culture.
In your course
Psychodynamic theories, and how clinical theories differ from experimental evidence.
Important context
Noba dates the visit to 1909 but does not discuss the theory. Psychoanalysis rested on case material, and its claims need separate evidence before being treated as findings.
It argued that perception organizes sensations into wholes instead of adding up separate elements.
In your course
Perceptual organization and the Gestalt principles.
Important context
The paper is "Experimentelle Studien über das Sehen von Bewegung" (1912). Wertheimer's principles of organization appeared later, in 1923. The story of the train ride that inspired it is an anecdote.
It is the standard classroom example of classical conditioning of emotion, and of how not to run a study.
In your course
Classical conditioning, generalization, and research ethics.
Important context
One child, no deconditioning, and a design that would not be approved today. The authors report that Albert left the hospital before any removal of the fear could be tried.
Pavlov's method made learning from signals a topic for precise physiological measurement.
In your course
Classical conditioning: acquisition, extinction, and generalization.
Important context
The linked lectures are the 1927 translation by G. V. Anrep. Pavlov's earlier papers on conditioning appeared before this date, and the lecture text uses the term "signal reflexes" more than "conditioned."
It is a starting point for modern research ethics, written in response to atrocities committed under the name of research.
In your course
Informed consent and why ethics review exists.
Important context
The judges revised an earlier set of six points into ten. The USHMM notes the code's legal force was not well established, though it influenced later ethics statements.
It illustrates how consequences can shape behavior even when the link is accidental.
In your course
Operant conditioning and schedules of reinforcement.
Important context
Skinner's interpretation, and his comparison to human rituals, is an argument; later researchers have proposed other explanations. This is one short report with a handful of birds.
It helped bring information and capacity limits into the study of memory and attention.
In your course
Short-term memory, chunking, and the cognitive revolution.
Important context
The paper compares two kinds of limits and uses "seven" loosely. Later work on working memory reports different capacity estimates depending on the task.
It linked a brain region to the formation of new memories.
In your course
The biology of memory and what case studies can show.
Important context
A small group of surgical patients, with H.M. as the best-known case. Case reports show what loss follows damage, not how a healthy brain divides the work.
It challenged the view that attachment grows only from being fed.
In your course
Attachment, and the ethics of animal research.
Important context
Harlow wrote that contact comfort mattered far more than feeding. The studies relied on isolating infant monkeys, a practice that raises serious welfare concerns today.
It suggested that people can change attitudes to fit what they have done.
In your course
Attitudes, cognitive dissonance, and self-justification.
Important context
Eleven of 71 participants were excluded, leaving 20 per group, all male Stanford students. Some measures in the paper were only weakly consistent with the theory.
It gave experimental support to learning by observation.
In your course
Social learning, modeling, and debates about media and aggression.
Important context
The study used 72 children from one Stanford nursery school and measured imitation in a lab room. It does not show that real-world violence follows from watching it.
It showed how far ordinary people may go when an authority tells them to.
In your course
Obedience, situational influence, and the ethics of deception and stress.
Important context
The counts come from the paper's abstract; the original sample was 40 men, from secondary sources. The study is also a standard case in debates about deception and participant distress.
It sharpened public debate about psychiatric diagnosis and hospital care.
In your course
Diagnosis, labeling, and how to evaluate a dramatic claim.
Important context
Contested. Robert Spitzer criticized the study's method and conclusions, and Susannah Cahalan's 2019 book argues that Rosenhan misrepresented some data. Treat it as a case of historical influence, not settled evidence.
It targets publication bias and selective reporting at the point of peer review.
In your course
Preregistration, open science, and how journals shape evidence.
Important context
Chambers' 2013 editorial is the origin cited; the claim that Cortex was first rests on his and colleagues' accounts. The 2013 launch was in neuroscience and later spread to psychology journals.
It turned discussion about replication into data and encouraged open materials and larger samples.
In your course
Replication, effect sizes, and interpreting a single study.
Important context
In the abstract, 36% of replications were significant against 97% of originals. The studies came from three journals, and a published comment by Gilbert and colleagues disputes the paper's statistical interpretation.
This is a selected teaching chronology for an introductory psychology course, not a complete or globally representative history. It leans toward European and North American research, and it has few entries between 1980 and 2009. Each entry links to sources and explains its historical context. This initial selection is still being reviewed against the full texts.
Dates mean different things. A publication year is when a work appeared, a study date is when research was reported, and an institutional date marks a society, laboratory, or policy. An entry that influenced the field is not necessarily correct, and the notes say where later work has qualified a classic.
This is a history and learning resource. It offers no medical advice and no diagnostic tools. The site has no tracker; your text size choice is stored only in your browser.
c. 400 BCE
A Greek medical text places thought in the brain
Date type
Publication year
Topic
History & ideas
Summary
On the Sacred Disease argues that epilepsy has a natural cause and that the brain is the organ of thought, feeling, and sensation.
Why it matters
It is an early surviving argument that mental life has a bodily basis that can be studied without appeal to the divine.
Important context
The work belongs to the Hippocratic Corpus, a collection by several authors, so the author and date are uncertain. "c. 400 BCE" is a convention. The essay is medical philosophy, not experimental evidence.
A systematic treatise on living things and their capacities, including perception, imagination, and thought.
Why it matters
It treats sensation, memory, and reasoning as natural subjects of inquiry, a template that later scholars argued with for centuries.
Important context
The date is approximate and the text circulated in copies and translations. It is philosophy and natural observation, not experiment, and modern readers disagree about how to interpret key terms.
Elements of Psychophysics states, in precise laws, how physical stimulation relates to what people experience.
Why it matters
It showed that experience could be tied to measurable stimuli, which made sensation a topic for laboratory work.
Important context
The entry marks the measurement program. Fechner also held broader philosophical views about mind and body that are a separate matter from his methods.
A dedicated laboratory helps establish psychology as an experimental science.
Why it matters
Questions about the mind become questions researchers can test with controlled methods.
Important context
The Noba history calls 1879 a popular date for the science's beginning rather than a precise founding, and it credits Wundt by convention. Other early laboratories and research programs existed.
Systematic experiments turn memory into a measurable subject.
Why it matters
He showed that memory could be studied with controlled procedures and repeated measurement.
Important context
This is the 1885 German publication; the English translation by Ruger and Bussenius appeared in 1913. Lists of syllables were an artificial task, so the results do not cover everyday memory.
G. Stanley Hall invites colleagues to Clark University, and a small society for psychology begins.
Why it matters
Professional societies give a field shared standards, meetings, and journals.
Important context
A U.S. milestone, not a global one. Fernberger names seven men at the July 8 meeting and 31 elected members; later accounts give other figures for who attended.
She becomes the first woman to earn a doctorate in psychology in the United States, and later serves as APA president.
Why it matters
Women were barred from degrees at many universities, and her career shows how access shaped who did research.
Important context
The "first" claim is the APA's wording. In the same year Harvard refused to grant Mary Whiton Calkins a degree although she had completed her doctoral work.
Hungry cats learn to escape from boxes, and escape times fall over repeated trials.
Why it matters
It offered a measurable account of learning from consequences that led to the law of effect.
Important context
The 1898 monograph is the original. The chapter linked here is from the 1911 expanded book, so the text and the date differ. Animal results do not automatically transfer to people.
Binet describes a way to assess children's intellectual level
Date type
Publication year
Topic
Development
Summary
A practical set of tasks is designed to identify schoolchildren who need extra help.
Why it matters
It started standardized ability testing and the debates about what such tests can and cannot show.
Important context
The scale is usually credited to Binet and Théodore Simon; the translation linked here lists Binet as author. Binet limited the method to a child's present level, not a fixed measure of innate ability.
G. Stanley Hall hosts Sigmund Freud in the United States, his only visit, which brings psychoanalysis to American audiences.
Why it matters
Psychoanalytic ideas about unconscious motives entered American psychology and popular culture.
Important context
Noba dates the visit to 1909 but does not discuss the theory. Psychoanalysis rested on case material, and its claims need separate evidence before being treated as findings.
Two briefly flashed lights look like one moving light, and the result launches Gestalt psychology.
Why it matters
It argued that perception organizes sensations into wholes instead of adding up separate elements.
Important context
The paper is "Experimentelle Studien über das Sehen von Bewegung" (1912). Wertheimer's principles of organization appeared later, in 1923. The story of the train ride that inspired it is an anecdote.
Watson and Rayner report conditioned fear in a baby
Date type
Study or experiment
Topic
Learning
Summary
A single infant, called Albert B., is conditioned to fear a white rat by pairing it with a loud sound.
Why it matters
It is the standard classroom example of classical conditioning of emotion, and of how not to run a study.
Important context
One child, no deconditioning, and a design that would not be approved today. The authors report that Albert left the hospital before any removal of the fear could be tried.
Lectures on the dog's salivary reflex describe how neutral signals can come to trigger a bodily response.
Why it matters
Pavlov's method made learning from signals a topic for precise physiological measurement.
Important context
The linked lectures are the 1927 translation by G. V. Anrep. Pavlov's earlier papers on conditioning appeared before this date, and the lecture text uses the term "signal reflexes" more than "conditioned."
The Nuremberg Code sets limits on human experiments
Date type
Historical event
Topic
Methods & ethics
Summary
The Doctors' Trial judgment states that voluntary consent of the research subject is essential.
Why it matters
It is a starting point for modern research ethics, written in response to atrocities committed under the name of research.
Important context
The judges revised an earlier set of six points into ten. The USHMM notes the code's legal force was not well established, though it influenced later ethics statements.
Pigeons fed on a fixed clock develop repeated odd behaviors, which Skinner explains as accidental reinforcement.
Why it matters
It illustrates how consequences can shape behavior even when the link is accidental.
Important context
Skinner's interpretation, and his comparison to human rituals, is an argument; later researchers have proposed other explanations. This is one short report with a handful of birds.
Miller describes limits on how much we can hold in mind
Date type
Publication year
Topic
Memory
Summary
"The Magical Number Seven, Plus or Minus Two" argues that immediate memory is limited by the number of chunks.
Why it matters
It helped bring information and capacity limits into the study of memory and attention.
Important context
The paper compares two kinds of limits and uses "seven" loosely. Later work on working memory reports different capacity estimates depending on the task.
Scoville and Milner report memory loss after hippocampal surgery
Date type
Publication year
Topic
Memory
Summary
A paper describes severe loss of recent memory after surgery on the medial temporal lobes, including the patient later known as H.M.
Why it matters
It linked a brain region to the formation of new memories.
Important context
A small group of surgical patients, with H.M. as the best-known case. Case reports show what loss follows damage, not how a healthy brain divides the work.
Infant rhesus monkeys spend far more time on a cloth surrogate than a wire one, whichever one gives milk.
Why it matters
It challenged the view that attachment grows only from being fed.
Important context
Harlow wrote that contact comfort mattered far more than feeding. The studies relied on isolating infant monkeys, a practice that raises serious welfare concerns today.
Students paid $1 to say a dull task was fun rated it more favorably than students paid $20.
Why it matters
It suggested that people can change attitudes to fit what they have done.
Important context
Eleven of 71 participants were excluded, leaving 20 per group, all male Stanford students. Some measures in the paper were only weakly consistent with the theory.
Bandura shows children imitating aggressive models
Date type
Study or experiment
Topic
Social psychology
Summary
Preschoolers who watched an adult act aggressively copied much of that behavior later.
Why it matters
It gave experimental support to learning by observation.
Important context
The study used 72 children from one Stanford nursery school and measured imitation in a lab room. It does not show that real-world violence follows from watching it.
In the first paper, 26 participants went on to the highest shock level on the generator, although the learner received no real shocks.
Why it matters
It showed how far ordinary people may go when an authority tells them to.
Important context
The counts come from the paper's abstract; the original sample was 40 men, from secondary sources. The study is also a standard case in debates about deception and participant distress.
Rosenhan publishes "On Being Sane in Insane Places"
Date type
Study or experiment
Topic
Clinical psychology
Summary
Healthy volunteers who reported hearing voices were admitted to psychiatric hospitals and diagnosed.
Why it matters
It sharpened public debate about psychiatric diagnosis and hospital care.
Important context
Contested. Robert Spitzer criticized the study's method and conclusions, and Susannah Cahalan's 2019 book argues that Rosenhan misrepresented some data. Treat it as a case of historical influence, not settled evidence.
The journal agrees to review study plans before data are collected, so publication does not depend on the results.
Why it matters
It targets publication bias and selective reporting at the point of peer review.
Important context
Chambers' 2013 editorial is the origin cited; the claim that Cortex was first rests on his and colleagues' accounts. The 2013 launch was in neuroscience and later spread to psychology journals.
The Open Science Collaboration reports replication results
Date type
Study or experiment
Topic
Methods & ethics
Summary
Researchers repeat 100 studies and find that fewer than half give clear support, with smaller average effects.
Why it matters
It turned discussion about replication into data and encouraged open materials and larger samples.
Important context
In the abstract, 36% of replications were significant against 97% of originals. The studies came from three journals, and a published comment by Gilbert and colleagues disputes the paper's statistical interpretation.