Getting into the spirit of giving during the holiday season may seem like a struggle, but it turns out generous people aren't fighting the urge to screw others over, as some have suggested. Instead, generosity - or the desire for fairness - seems automatic and arises from activation in a brain area that controls intuition and emotion.

Neuropsychologists define "prosocial" people as those who prefer to share and share alike, and "individualists" as those who are primarily concerned with maximising their own gain.

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Haruno, along with Christopher Frith of University College London used functional MRI to scan the brains of 25 prosocial people and 14 individualists (presorted using a standard behavioral test) while they rated their preference for a series of money distributions between themselves and a hypothetical other person. As expected, the prosocial group preferred even splits while the individualists favoured distributions where they got the most money.
Active amygdala

A less predictable finding was that the only brain region that differed in activity between the two groups was the amygdala. When presented with unfair money distributions the activity in the amygdala increased significantly in prosocial people but not in the individualists. "And the more they disliked the split, the more activity you saw in this region," says Frith.

"The amygdala tends to respond automatically, without thought, or even without awareness," says Frith. Combined with the fact that there was no difference in activity in the prefrontal cortex - responsible for suppressing urges - this suggested that the suppression theory might not be borne out.