Cocaine and amphetamines can greatly enhance sexual motivation because they stimulate the release of large amounts of dopamine. Simply doing a lot of mental work can loosen the reins. Executive thinking involves comparatively massive brain real estate—the human prefrontal cortex is about ten times larger than the hypothalamus—and consumes much more energy. Loewenstein has found that doing math problems before being offered cookies can lower a dieter’s resistance to the reward of a good Toll House: all that thinking has drained our executive brain’s batteries.
