It might seem obvious that, for most people, happiness is positively correlated with friendships. But a paper published last month in the British Journal of Psychology found one notable exception: Extremely intelligent people become less happy when they spend more time with their friends.

Researchers, led by psychology professor Norman Li from Singapore Management University, used evolutionary psychology to explain why some people are happier than others. They theorized that situations that led to positive consequences for our ancestors would also boost happiness today.

People who live in rural areas tend to be happier than those in urban areas, they argue, because our ancestors lived in groups of 150 people and struggled to maintain cooperation and reciprocity in larger groups. Living in larger groups could then create feelings of unease and discomfort.

Meanwhile, friendships could be key to happiness because our ancestors relied on such relationships to overcome hunting challenges and share childrearing duties.

But, the researchers posit, these rules would not hold for extremely intelligent people, who would have less difficulty living in high population areas and not associating with friends.

These theories held when the researchers analyzed data from the National Longitudinal Study of Adolescent Health survey of more than 15,000 people aged 18 to 28. In fact, they wrote, “intelligent individuals even appeared to become more satisfied with life when their frequency of socialization with friends was lower.”

Of course, we’re no longer living in the same circumstances as our ancestors, thanks to the wonders of technological advancement. And the researchers argue that more intelligent people simply have less trouble adapting to our new reality. Those with higher IQs have less of a need to rely on our ancestral hunting and childrearing networks, and can adjust to life in high-population environments.

But the researchers’ theory is not the only explanation for such findings. Carol Graham, a Brookings Institution researcher who studies the economics of happiness, told the Washington Post that she had a slightly different interpretation. More intelligent people “are less likely to spend so much time socializing because they are focused on some other longer term objective,” she said.

In other words, work is so important to them that they don’t have time to waste with friendships.