Being honest, even when it may be advantageous to lie, takes more self-control. Those were the findings of a new study led by Ming Hsu of the University of California, Berkeley. They linked damage to the brain’s prefrontal cortex, a region that controls impulses, to an inability to control self-interests. Hsu says the study involved a money-splitting game between participants with damage to their prefrontal region and those with healthy brains.

"So, you tell them either option A is better than option B for you or option B is better than option A for you. So essentially this will be like saying, car A is really good for you, even though when I know car B is really the better one for you. What we found is that people who don’t have damage to this brain region are willing to sacrifice quite a bit of material interest in order to not have to be dishonest."

Hsu says this research supports the hypothesis that humans are inherently self-interested.

"People like economists and behavioral ecologists have long argued that self-interest is the basic impulses of human behavior."