History of Psychology

Plato divided the soul into reason, spirit, and appetite in conflict — an early model of an inner life with competing parts that still echoes in psychology.

Aristotle's treatise on the soul was the first systematic psychology, analysing perception, memory, imagination, and thought as functions of the living being.

Galen tied temperament to bodily fluids — sanguine, choleric, melancholic, phlegmatic — the first influential theory of personality and its physical roots.

Avicenna mapped the mind's 'internal senses' — memory, imagination, estimation — and described emotional and psychosomatic states with clinical care.

Descartes split the thinking mind from the mechanical body, posing the mind-body problem that has framed the science of the mind ever since.

Locke argued the mind begins as a blank slate written on by experience, and that ideas link by association — foundations of empiricist psychology.

Hume made the association of ideas and the primacy of emotion over reason a systematic account of human nature that anticipated much of later psychology.

Kant argued the mind actively shapes experience through built-in forms of space, time, and category — an idea that would return in cognitive psychology.

Fechner measured how sensation relates to physical stimulus, proving the mind could be studied quantitatively and giving psychology its first laws.

Broca traced loss of speech to a specific brain region, giving the first hard evidence that distinct mental functions live in distinct parts of the brain.

Wilhelm Wundt opened the first laboratory dedicated to experimental psychology in Leipzig, the moment usually taken as the birth of psychology as a science.

Galton pioneered the measurement of individual differences and statistical methods like correlation, founding the troubled tradition of mental testing.

By memorising nonsense syllables on himself, Ebbinghaus charted how memory decays over time, bringing rigorous experiment to the higher mental processes.

William James's sweeping textbook framed the 'stream of consciousness', habit, and emotion, and launched the functionalist study of what the mind is for.

Freud claimed that hidden unconscious drives, formed in childhood, govern much of behaviour, and built psychoanalysis to bring them into the light.

Freud's book cast dreams as the 'royal road to the unconscious', launching psychoanalysis and a century-long argument about the hidden mind.

Breaking with Freud, Adler founded individual psychology around the drive to overcome inferiority and the pull of social belonging over sexuality.

Jung's analytical psychology introduced the collective unconscious, archetypes, and personality types, reaching deep into culture, myth, and religion.

Pavlov showed that a neutral signal paired with food could itself trigger salivation, revealing learning as a lawful, measurable association.

Thorndike found that behaviours followed by satisfaction are repeated and those followed by discomfort fade — the reinforcement principle in embryo.

Against the atomism of both behaviourism and introspection, the Gestalt school showed the mind perceives organised wholes — 'the whole is other than the parts'.

Watson declared that psychology should abandon the mind entirely and study only observable behaviour, setting the agenda for decades of research.

Skinner showed how reward and punishment shape voluntary behaviour, built the experimental technology of reinforcement, and pushed behaviourism to its peak.

Maslow arranged human motives from basic survival up to self-actualisation, offering a hopeful picture of psychology as the study of human potential.

Rogers built client-centred therapy on empathy and unconditional positive regard, trusting people's own drive toward growth rather than the analyst's authority.

The Diagnostic and Statistical Manual gave clinicians a shared catalogue of mental disorders, standardising diagnosis — and sparking lasting debate over it.

Piaget showed that children think in qualitatively different stages, founding developmental psychology and the study of how understanding is built.

Drawing on the computer as a metaphor, researchers brought the mind back into science as an information processor, ending behaviourism's monopoly.

George Miller's paper showed that short-term memory holds only about seven items, a founding quantitative result of the new cognitive psychology.

Festinger showed that holding conflicting beliefs creates discomfort people resolve by changing their minds, a cornerstone of social psychology.

Chomsky argued that reinforcement cannot explain how children learn language, a decisive blow to behaviourism and a spur to the study of the mind's structure.

Milgram found ordinary people would deliver apparently dangerous shocks when an authority told them to, a disturbing lesson about situation over character.

Bandura's Bobo doll studies showed that people learn by watching others, adding observation and imitation to the reward-based picture of learning.

Bowlby argued that the infant's bond with a caregiver is a deep biological need shaping later relationships, founding attachment theory.

Aaron Beck showed that changing distorted thoughts can relieve depression, founding cognitive behavioural therapy — now the most evidenced talking cure.

Studying a sea slug's neurons, Kandel revealed how learning physically changes the connections between nerve cells, grounding memory in molecules.

Sperry's studies of patients with severed hemispheres showed the two halves of the brain can process the world differently, reshaping views of consciousness.

The 'decade of the brain' fused psychology with neuroscience, seeking the neural machinery behind attention, emotion, decision, and the self.

fMRI let researchers watch the living brain at work, letting cognitive neuroscience link specific thoughts and feelings to patterns of neural activity.

Decades of statistical work converged on five broad traits — openness, conscientiousness, extraversion, agreeableness, neuroticism — as a map of personality.

Seligman turned the field toward strengths, wellbeing, and flourishing, arguing psychology should study what makes life good, not only what makes it fail.

Kahneman's work on the fast, intuitive and slow, deliberate systems of thought and their biases won a Nobel and bridged psychology with economics.

Kahneman's bestseller brought decades of research on judgment and bias to a wide public, making the two systems of the mind common cultural currency.

When many famous findings failed to reproduce, psychology confronted flawed methods and began reforming toward preregistration, larger samples, and openness.