Results showed that people with the variant did worse on both tests than the other participants, and they remembered less the second time. "Behavior derives from dozens and dozens of neurophysiologic events, so it's somewhat surprising this exercise bore fruit," Cramer said.

The gene variant isn't always bad, though. Studies have found that people with it maintain their usual mental sharpness longer than those without it when neurodegenerative diseases such as Parkinson's, Huntington's and multiple sclerosis are present.

"It's as if nature is trying to determine the best approach," Cramer said. "If you want to learn a new skill or have had a stroke and need to regenerate brain cells, there's evidence that having the variant is not good. But if you've got a disease that affects cognitive function, there's evidence it can act in your favor. The variant brings a different balance between flexibility and stability."

A test to determine whether someone has the gene variant is not commercially available.

"I'd be curious to know the genetics of people who get into car crashes," Cramer said. "I wonder if the accident rate is higher for drivers with the variant."

Source: University of California - Irvine