There was a study done to see if the urban legend that men think about sex once every seven seconds is true. Psychologists asked 163 college women and 120 college men to carry around small tally counters, and asked them to record each time they thought about food, sleep, or sex. On average , the men had sexual thoughts slightly more than once each waking hour and women about half that. But the men had thoughts about food and sleep about as often as sexual thoughts.
The psychologists theorized that men could be more aware then women of their own physical state at any given time, or that men are more comfortable recording such thoughts than women. In the women who reported they care more about what others thought about them, were less likely to report food or sexual thoughts - perhaps because of the social stigma of food and sex with females. Women were equally as likely to report sleep-related thoughts, perhaps because there is no stigma with sleeping.