Big-hearted? The Amygdala Can Tell

What can brain chemistry teach us about generosity? A new study by Masahiko Haruno of Japan's Tamagawa University and Christopher Frith of the UK's University College London shows that the brains of equality-oriented people react differently to unfairness than do personal-gain-focused individuals, according to the New Scientist.

The study compared two groups of subjects — one "prosocial," or oriented toward fairness, and the other "individualist," or oriented toward maximizing personal benefit — divided based on a personality test. The researchers used a functional MRI to scan subjects' brains while they ranked a series of hypothetical situations involving money distribution between themselves and another person.

Not only did the prosocial group prefer scenarios that involved fair distribution, as expected, but when confronted with situations that would benefit one person over another, the scan showed activity in the part of the brain called the amygdala. Individualists didn't exhibit the same type of activity.

This is a telling finding because the amygdala tends to react automatically to stimuli, which suggests that equality-minded people are not just suppressing selfish urges, as some claim, but are simply more oriented toward fairness. It's not yet clear how much of the effect is genetic and how much is determined by a person's upbringing or other experiences, but Haruno says the results could possibly lead to insight about encouraging more prosocial societies.

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