Patients with damage to a brain region called the dorsolateral prefrontal cortex are more likely to favor selfish decisions over fairer ones, reports a study published this week in Nature Neuroscience.

Ming Hsu and colleagues looked at patients who had sustained brain damage to either their dorsolateral prefrontal cortex or their orbitofrontal cortex (different areas of the brain region behind the forehead), as well as people without brain damage. The participants were asked to play economic games that pitted self-interest against fair play when deciding how to cooperatively split money.

The authors found that compared to the other two groups, the patients with damage to their dorsolateral prefrontal cortex were more likely to lie to their partner to prevent them from having better financial gain compared to themselves. By modeling these results, Hsu and colleagues also concluded that the dorsolateral prefrontal cortex normally helps to promote honesty over self-interest, and damage to this region impairs this ability.