" There may be a genetic basis to how much dopamine each of our brains produces. The gene that codes for the production of dopamine is called DRD4 (dopamine receptor D4) and is located on the short arm of the eleventh chromosome. When dopamine is released by certain neurons in the brain it is picked up by other neurons that are receptive to its chemical structure, thereby establishing dopamine pathways that stimulate organisms to become more active and reward certain behaviors that then get repeated. If you knock out dopamine from either a rat or a human, for example, they will become catatonic. If you overstimulate the production of dopamine, you get frenetic behavior in rats and schizophrenic behavior in humans. "

― Michael Shermer , The Believing Brain: From Ghosts and Gods to Politics and Conspiracies How We Construct Beliefs and Reinforce Them as Truths