If you're familiar with the ultimatum game, then perhaps you've encountered this scenario: a stranger sitting next to you gets $ 10, and he's given the chance to share the money with you. He decides how much he'll give to you and how much he gets for himself, but only on one condition: If you refuse his offer, neither of you gets any money at all.

Before you play this game, let the scientists at the University of Zurich give you an small insight. Ernst Fehr and Daria Knoch have published an experiment which concerns the dorsolateral prefrontal cortex (DLPFC) in the brain and its relation to how we decide in the "Ultimatum". Basically, the study has shown that when the DLPFC is switched off via transcranial magnetic stimulation, people who played the game change the way that they played it. A person may actually refuse the money if the stranger decides to offer him a low amount, just to punish him and fulfill his sense of justice. When the DLPFC became inactive, he tended to accept the money, however low the amount given to him. Thus, emotions became overwhelmed with the rational side that catered to self-interest.

The DLPFC, it turns out, is a crucial part in the brain that balances emotion and reason. And the fact that it doesn't develop fully until the teenage years is what possibly explains adolescent selfishness.

Now, of course, we're talking about a stranger here. You might decide differently if it's your closest pal, or if you're really out of cash. When this is the case, you have no choice but to willingly accept how much you're offered, because it won't violate your sense of justice at all. The study has only proven that in extreme cases involving terrorists, suicide bombers or gangsters, the brain's DLPFC provides a potent explanation for their vengeful acts, but to put it in perspective, one has to remember that we're all subject to this type of behavior, whether we realize it or not.