Many straight men, as many a straight lady can tell you, have an annoying habit of mistaking basic manners — a smile, a laugh, even a simple polite reply — for flirtation. Recently, a team of Norwegian psychologists decided to investigate this romantic mystery, and they concluded that this sexual misperception — as they term the phenomenon — may be at least partially explained by evolution. For more on that, watch the latest episode of the Science of Us animated video series. You can also check out last week’s episode, all about the bright side of having a bad attitude, or explore older episodes from the series. And, as always, be sure to come back next week for another animated exploration of the oddities of human behavior.