Our happy hour fact to amaze your drinking buddies with.

The human brain is only capable of maintaining 150 stable relationships.

In 1992, British anthropologist Robin Dunbar came up with 150, which was dubbed "Dunbar's Number," after studying social groupings throughout history. Now, with sites like Facebook pushing the number of declared friendships claimed by enthusiastic social media consumers into the thousands, Dunbar wanted to retest his formulation.

Defining "friends" as those you contact at least once a year, the Oxford professor analyzed Facebook traffic. "The interesting thing is that you can have 1,500 friends but when you actually look at traffic on sites, you see people maintain the same inner circle of around 150 people that we observe in the real world," Dunbar says.

We're glad he cleared that up, because it made us dizzy to think that some of our friends were juggling 1,327 other friendships. Now if someone could explain the mystery of the "poke" function ...