Friendship between women: A woman doesn’t go home one night. The next morning she tells her husband that she slept over at a friend’s house. The man calls his wife’s 10 best friends. None of them know anything about it.

Friendship between men: A man doesn’t go home one night. The next morning he tells his wife that he slept over at a friend’s house. The woman calls her husband’s 10 best friends, 8 of whom confirm that he had slept over, with 2 saying that he was still there.