Dopamine plays a lot of roles in the brain. If you kill off the cells that produce dopamine, the animal is not motivated to go out and do things. It’ll still enjoy something — like the sucrose solution you squeeze directly into its mouth — because the pleasure systems are fine. But they won’t pursue it. If you perform an action and you get more... See more

In this view, dopamine does not signify how pleasant an experience will be but how much value it has to the organism at that particular moment. Schultz notes that dopamine neurons do not distinguish among different types of reward. “They're only interested in the value,” he says. “They don't care whether it's food reward or liquid reward or money.... See more