According to a new study at the University of Kansas, it takes an average of 50 hours of hanging to become "casual" friends with someone instead of just acquaintances.
It takes 90 hours to become REAL friends. And if you want to be CLOSE friends, you'll need more than 200 hours together.
Obviously this doesn't apply to young kids. When you're five, you can make friends with someone in ten minutes.
The study also found that working together doesn't really count. You CAN become friends with a coworker after you've worked together for a while . . . but it takes longer than if you were just hanging out with them outside of work.
(Phys.org)