Gospic devised a lab-based study (the ultimatum game), to investigate the role of the amygdala in reactive aggression. The proposer offers to split money in a certain way with a responder. If the responder accepts the offer the money is split as proposed. But if the responder rejects the offer, neither gets the money. Researchers scanned responders in the game using fMRI to highlight areas of the brain. They found that when responders rejected unfair offers (an aggressive response) scans revealed heightened activity in the amygdala.