BERKELEY, CA — Researchers at the University of California in Berkeley reignited the age-old "nature or nurture" debate today by announcing the results of a year-long study into Ben Affleck's facial expressions.

The researchers claim the study, which will be published in a peer-reviewed journal within the next six months, proves that both Affleck's facial expressions — "determined" and "confused" — are the result of genetics rather than rearing.

"Since [Affleck] first burst zit-like onto the scene with Good Will Hunting I've wondered what caused his astonishing lack of emotional range," said project lead Dr David Fisker. "Now, thanks to our hard work over the last year, I can rest easy. It's a good feeling."

Fisker explained that all available evidence indicates the 32-year-old actor has just two facial configurations, one expressing determination and the other expressing confusion.

"He can do a mix of both, too, and look determined yet confused or confused yet determined, but that doesn't really count," said Fisker.

After a frame-by-frame analysis of all of Affleck's movies to date the team presented their proposal to the Department of Health and Human Services, where it was determined sufficient evidence existed for the team to receive government funding.

With the financial backing in place the team began interviewing Affleck's friends and family to determine if his facial expressions off-screen were as staggeringly restricted as on.

Matt Damon, co-author with Affleck of Good Will Hunting and long-time "close acquaintance" of the emotionally limited actor, confirmed their hypothesis.

"It's true, yeah. He's like that all the time," said Damon. "It was great when we were writing [Good Will] Hunting though because if I needed, say, determined dialog I'd just give him a jar to open and I'd be inspired by his face."

The researchers then moved on to addressing their most important question: is Affleck's inability to adopt a facial arrangement other than determined or confused a result of his genes or his childhood?

"We really had no idea when we started," said Dr Peter Ferguson, the team's head anthropologist. "It could've gone either way. So naturally the first thing we did was visit with his parents in Cambridge [Massachusetts]."

The researchers soon discovered compelling evidence for the theory that Affleck's condition is genetic.

"It was obvious from the very moment we met [Affleck's parents]," said Ferguson. "We were startled to discover that Ben's father, Tim, only ever looks confused, and his mother, Chris, only ever looks determined."