You know what's-his-face from I.T., or whoozis from accounting? While some of us have genuine trouble remembering names, new research suggests the average person can place 5,000 faces.

The exact numbers have been a mystery until now, thanks to researchers from the U.K.'s University of York, who literally put people to the test, having test subjects write down as many people they could remember.

After about an hour of scouring their memory for family members, co-workers, neighbors, former classmates, and just about everybody else, the subjects were presented with photos of famous people to see if they could name them, according to the researchers.

The scientists say their subjects could name between 1,000 and 10,000 people, putting the average at the middle mark. Dr. Rob Jenkins from the university's Department of Psychology, said, "Our study focused on the number of faces people actually know," adding, "we haven't yet found a limit on how many faces the brain can handle."

He explained that facial memory is a key part of human development. "The ability to distinguish different individuals is clearly important -- it allows you to keep track of people's behavior over time, and to modify your own behavior accordingly."

The test subjects had an average age of 24, however, making the scientists wonder what would happen to this type of memory as we age.