Social butterflies who shine at parties may get their edge from special genes that make them experts at recognizing faces. Scientists have found the strongest evidence to date that genes govern how well we keep track of who's who.

The findings suggest that face-recognition and other cognitive skills may be separate from each other, and independent of general intelligence. This could help explain what makes one person good at math but bad at music, or good at spatial navigation but bad at language

"People have wondered for a long time what makes one person cognitively different from another person," said cognitive psychologist Nancy Kanwisher of MIT, coauthor of the study published Jan. 7 in Current Biology. "Our study is one tiny piece of the answer to this question."

The ability to recognize faces is not just handy for cocktail parties, it's crucial for distinguishing friend from foe and facilitating social interactions. If face recognition increases our ability to fend off predators and find mates, there is an evolutionary drive to encode this ability in our genes.

To test this, Kanwisher's team looked at whether the ability to recognize faces runs in the family. They found that identical twins, who share 100 percent of their genes, were more similar in their face-recognition ability than fraternal twins, who share only 50 percent of their genes. This suggests the ability to recognize faces is heritable.

"This is the strongest evidence for a role of genes in face recognition abilities in humans," Kanwisher said.

Some scientists have proposed that IQ is a general factor: You are either smart at all mental abilities or weak across mental abilities. Others have suggested that each mental ability has its own separate hardware in the brain. The current results show that the latter is true, at least for face recognition.

"There’s an ongoing debate about whether the brain is divided into separate pieces that do completely independent things, or whether it's a general-purpose device," said psychologist Gary Marcus of New York University, who was not involved in the study. "This is some of the best evidence that genes could target a particular aspect of the mind."

It's unclear how the genes affect recognition, Kanwisher said. One option is that they determine how well you measure distances between the eyes and mouth. Another possibility is that the genes may make you more extroverted, and spending more time with people helps you get better at recognizing faces.

"We just can't tell which is true," Kanwisher said. "Our study shows that genes exert a specific influence on face-recognition ability, but it doesn't tell us which genes are involved, or how exactly they shape the relevant neural circuits."

Though the new findings suggest that additional cognitive skills could be rooted in an independent set of genes as well, it may not be true for abilities. Language, for instance, evolved much later than face perception.

"This may mean that language depends less on genes that evolved specifically for language, and that it's less separable from other aspects of the mind," Marcus said.

Kanwisher and the study's senior author, Jia Liu of Beijing Normal University, are planning future studies to examine the role of genes in language, spatial ability, math and a range of cognitive abilities.

Image: Flickr/sean_dreilinger

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