Danica Patrick and the dopamine effect? "It's a good bet she inherited her need for speed," says neurologist Malcolm Stewart, medical director of the Human Performance Lab at Presbyterian Hospital of Dallas. "She probably comes from a family of high dopamine producers." Dopamine is a brain chemical that acts as a messenger involved in reward, motivation and mood. People with high dopamine production tend to be risk-takers such as race car drivers, bungee jumpers, test pilots, astronauts and explorers, Stewart says."They ride motorcycles fast, get tattoos."