It turns out that dopamine is a chemical on double duty in the brain. Along with its role in motor commands, it also serves as the main messenger in the reward systems, guiding a person toward food, drink, mates, and all things useful for survival. Because of its role in the reward system, imbalances in dopamine can trigger gambling, overeating, and drug addiction - behaviors that result from a reward system gone awry.

Incognito: The Secret Lives of the Brain (ed. Vintage, 2011) - ISBN: 9780307379788