Psychology › Brain & biology › Neurotransmitters, the brain's chemical messengers
Dopamine, reward and prediction error
1958; reward signal 1997· Concept
Well replicatedStrong, repeated evidence.
A neurotransmitter for movement, motivation and learning; it signals when outcomes are better or worse than expected, not pleasure itself.
See it on the Psychology map →What it says
Swedish pharmacologist Arvid Carlsson showed in 1958 that dopamine is a neurotransmitter needed for movement; its loss causes Parkinson's disease. In the 1980s–90s Wolfram Schultz recorded monkey neurons: they fired at an unexpected juice reward, shifted to firing at a cue that predicted it, and dipped when a promised reward failed to come. In 1997 Schultz, Peter Dayan and Read Montague called this a 'reward prediction error', the same learning signal used in computer algorithms. Dopamine drives wanting and learning more than enjoying.
Why it matters
It explains why surprises motivate, why expected rewards lose their thrill, and how drugs, gambling and apps hook learning. Dopamine drugs treat Parkinson's; blocking dopamine treats psychosis.
Think of it like
Like a variance report on a rent roll: it flags the gap between budgeted and actual, not the rent itself.
The evidence
Status: well replicated. Carlsson's 2000 Nobel Prize, Schultz's monkey recordings and mouse experiments that switch dopamine cells on with light. Kent Berridge's rat studies separate dopamine-driven 'wanting' from 'liking'.
Open questions
Whether all dopamine signals are prediction errors: some track movement, novelty or threat. Popular 'dopamine detox' claims to reset brain chemistry have no scientific basis.
Connections (4)
▸Dopamine, reward and prediction error is one of the Neurotransmitters, the brain's chemical messengersWell replicated
The connection
Dopamine is one of the brain's 'modulating' neurotransmitters. Fewer than a million human neurons make it, clustered in the midbrain, yet their fibers reach wide areas and adjust how other circuits respond. It belongs to the same chemical family, the monoamines, as serotonin and norepinephrine, which is why many drugs affect several of them at once.
Who showed it and when
Arvid Carlsson's lab in Lund, Sweden, 1957–58, showed dopamine is a transmitter in its own right, not just a building block for norepinephrine as had been assumed.
The evidence
Carlsson reversed drug-induced Parkinson-like stiffness in rabbits with L-DOPA, which the brain turns into dopamine; it still treats Parkinson's, and he shared the 2000 Nobel Prize.
Open questions
Dopamine neurons can also release glutamate or GABA, blurring the neat 'one neuron, one chemical' picture; what this co-release does is still being studied.
▸Dopamine, reward and prediction error signals reward in Reinforcement and punishmentWell replicated
The connection
Dopamine supplies the teaching signal that reinforcement needs. A better-than-expected outcome makes dopamine neurons burst, strengthening whatever behavior came just before; a worse-than-expected one makes them dip. Once a reward is fully predicted, the burst moves to the earliest cue that predicts it. That is the cellular version of Thorndike's and Skinner's rules.
Who showed it and when
James Olds and Peter Milner found rats would press levers to stimulate reward areas at McGill in 1954; Wolfram Schultz recorded monkey dopamine neurons in Fribourg, Switzerland, in the 1980s–1990s.
The evidence
Recordings in monkeys and humans, plus experiments where switching on dopamine cells alone, with light, made mice learn and seek out a location, show the link is causal.
Open questions
Whether dopamine signals reward itself or importance more broadly: some dopamine cells respond to threats or surprises, and 'liking' a reward seems to rely on other chemicals.
▸Dopamine, reward and prediction error is hijacked in Addiction and substance use disordersWell replicated
The connection
Cocaine, amphetamine, opioids, alcohol and nicotine all raise dopamine in the brain's reward circuit, often far more than food or sex. That surge acts as a powerful teaching signal, stamping in cues and habits so craving grows, while repeated use dulls the response to everyday rewards.
Who showed it and when
Gaetano Di Chiara showed in 1988 that most abused drugs raise dopamine in rats; Nora Volkow's brain scans from the 1990s found fewer dopamine receptors in people with addiction.
The evidence
Animal studies, human brain imaging and reward-prediction research converge; blocking dopamine reduces drug-seeking in animals.
Open questions
'Hijacking' simplifies: dopamine drives wanting more than pleasure, and why only some users become addicted points to genes, stress and environment too.
▸Antipsychotic medications mostly block receptors for Dopamine, reward and prediction errorWell replicated
The connection
Most antipsychotics block dopamine D2 receptors, damping signals in brain pathways thought to be overactive in psychosis. The doses that work track how tightly each drug binds D2. Blocking dopamine in movement circuits also explains their Parkinson-like side effects. This evidence produced the 'dopamine hypothesis' of schizophrenia.
Who showed it and when
Arvid Carlsson linked antipsychotics to dopamine in 1963; in 1975–76 Philip Seeman in Toronto and Solomon Snyder at Johns Hopkins showed clinical doses match D2 binding strength.
The evidence
PET brain scans show the drugs work best when they occupy roughly 65 to 80 percent of D2 receptors; amphetamine, which releases dopamine, can trigger psychosis.
Open questions
Why dopamine blockers do little for low motivation, flat emotion and thinking problems is unclear. Cobenfy (2024) works through acetylcholine receptors instead, so dopamine is not the whole story.