Revenge feels sweet, and Swiss researchers said on Thursday they have the brain scans to prove it. In a study investigators said might help explain how social norms arose and regulate behavior, brain centers linked to enjoyment and satisfaction lit up in young men who punished others for cheating them. Dominique de Quervain of the University of Zurich and colleagues tested 15 male students, telling them they were doing an economic study. The men all sat in positron electron tomography, or PET scanners, that recorded brain activity. In the study, published in the journal Science, they paired the men in an exchange of cash. Player A could give all or some of his money to player B, who could then give some or none of it back. If the first player gave all his money, the amount was quadrupled and player B could share the reward with player A. This scenario would obviously benefit both the most, so player A had an incentive to share. If player B declined to share, player A could punish him by taking away imaginary points or taking away money. --More 2309 Local Time 2009 GMT
