Our happy hour fact to amaze your drinking buddies with. In an experiment involving lab rats, sex was correlated with adult brain growth. Since previous studies have shown that stressful, unpleasant situations can hinder brain growth, researchers from Princeton University wanted to see if stressful but pleasurable situations -- like sex -- would achieve the opposite effect. So, they divided male lab rats into three groups: The rats in one group were given sex partners daily, the second group got set up with female companionship once every two weeks and the third group got nothing at all. The rats that...