Definition
Dopamine is a neurotransmitter most often described, loosely, as the brain's pleasure chemical. Behave corrects that picture sharply: dopamine is the chemistry of anticipation and motivation, not reward itself. It surges most strongly not when you receive something good, but when you expect it and begin the work of getting it.
It is released by neurons in deep midbrain structures that project to reward and decision-making circuits. Dopamine is what turns a signal of future reward into the drive to pursue it.
Why it matters
How it works
Dopamine neurons compute a reward-prediction error. An unexpected reward produces a burst; a reward exactly as predicted produces little; a predicted reward that fails to arrive produces a dip. This error signal is how the brain learns which cues are worth caring about.
As a cue reliably predicts a reward, the dopamine surge migrates from the reward to the cue itself — anticipation becomes the engine. Sapolsky highlights one twist: dopamine release peaks not at certain reward but at uncertain reward, when the probability is around fifty percent. The brain is wired to be most motivated by maybe.