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These days, people roll their eyes to signal their disapproval, perhaps in response to a melodramatic Facebook post or a presidential press conference. But, according to Slate's Forrest Wickman, we've only been using it that way since the mid-20th century. At the turn of the 17th century, lust, not annoyance, made you roll your eyes. In William Shakespeare's 1594 poem "The Rape of Lucrece," the Bard describes the rapist Sextus Tarquinius as gazing at his victim's bed while "rolling his greedy eyeballs in his head." John Milton's 1667 poem "Paradise Lost" talks about women who are "empty of all good" whose only purpose is to "troll the tongue and roll the eye." Even as late as 1950, country singer Hank Penny sung about a woman who would "roll those big brown eyes" to tempt an ex-lover.

People would also roll their eyes in fear or anger, the way a frightened horse might. In 1857, Charles Dickens wrote about a dying woman who "rolled her eyes fearfully." Likewise, you might remember Maurice Sendak's 1963 children's book "Where The Wild Things Are," in which the monsters "roll their terrible eyes."

The expression's modern meaning began to take hold around the 1900s. In 1927, the third ever "Hardy Boys" book depicted a teen doing what modern teens do best: "'We'd better eat.' Iola giggled. 'My poor brother is suffering.' 'I sure am!' Chet rolled his eyes." In 1964, a character rolls her eyes at her lover's excuses, saying "Oh, brother!" The expression didn't really take hold of the popular consciousness until the 1980s, when published mentions of it began to skyrocket.

But when it comes to why you or I roll our eyes at someone's groan-worthy pun or cutesy couple's selfie, there's been a lot of research. We generally roll our eyes out of disapproval or contempt, perhaps as a way of shielding our gaze from something unpleasant. The action is most common among teens, especially teen girls. This makes sense, according to the authors of a 2012 paper on social aggression in teen girls, since "among both children and adults, females tend to be more skilled both in the expression and decoding of nonverbal communication." Boys, on the other hand, are more likely to show aggression physically. (Don't despair, parents of teen girls. The New York Times says that when daughters roll their eyes at their parents, it's just a way of voicing objection without resorting to all-out defiance.)

But if we haven't always rolled our eyes for the same reason, are we just faking it? Not necessarily. Contrary to popular belief, the vast majority of facial expressions aren't shared universally. When researchers asked indigenous people in Papua New Guinea to identify the emotion in a series of photos of facial expressions, their responses were very different from those in Western cultures: a gasping face you might guess was frightened, they saw as threatening; and scowling, pouting, and nose-scrunching got a mix of responses. If the emotion behind facial expressions changes by culture, it can certainly change by era. Just one more thing to keep in mind when you finally get your hands on a time machine.