The key element to understanding embarrassment as a human emotion, according to experts, is the fact that we're a deeply social species that hangs around in groups, and that those groups have been necessary to our survival over the millennia. They call embarrassment a "prosocial" behavior, one that accompanies some kind of break of social mores (farting in public, calling somebody a stupid name, stealing their lunch) and signals that you're sorry and won't be doing it again.

If we were loners, we likely wouldn't have developed facial and bodily signals that we regretted and were anxious about something we'd just done, because we'd have nobody to signal to. And that signaling goes beyond just blushing and biting our lips. There's an intriguing tie, psychological experiments show, between people who are more liable to show embarrassment and those who are also more likely to display other "prosocial" behaviors, like kindness and generosity. A lack of embarrassment isn't actually a desirable aim in social situations: to act completely without shame means that you're either not aware of the social rules that bind that group together, or don't care about them. Not exactly friendly. Blushing, on the other hand, demonstrates that you're aware of the transgression and also that you're experiencing pain as a self-punishment for doing it. That sort of thing reinforces the original rules.

The technical term for a display of embarrassment in social contexts, according to experts, is an "appeasement behavior." Professor Dacher Keltner analyzed the behavior of many different species that live in groups, from elephant seals to primates, and found that openly showing a kind of embarrassment at having done something unwise or risky (going for somebody's food and being caught, for instance) is pretty common. It's a deescalation technique, designed to deflate possible tensions by openly being submissive and admitting that you were wrong. "At the heart of the embarrassment display, as in other species’ appeasement behaviors," he writes for the University of Berkeley, "is weakness, humility, and modesty." And that can help survival in a context where you're both always competing and need to depend on others to survive.

That tug-of-war between fighting and cooperating with other people in your closest social circle may also be at the root of socially anxious behaviors, which is what embarrassment is: an experience of humiliation and potential loss of face with others. We experience embarrassment, according to one hypothesis, because we have done something that threatens our social standing, and therefore creates problems for our future. In Shyness & Embarrassment: Perspectives From Social Psychology, experts explain that "display behavior" is something common among many animals that greases the wheel of our social success. (Birds do courtship dances; we make jokes.) If we put on a socially acceptable show, we'll get more friends, have more access to resources, and attract more mates. "It is the evaluation of our own display behavior and the expected social responses to it," they write, "that are at the heart of social anxiety." Embarrassment is a response to faux pas that might cost us dearly, and is our physically evolved response to try and lessen the damage.

One of the special aspects of embarrassment, as a social behavior, is that it's contagious. Cringe humor is based on this idea: that we feel embarrassment for those who are embarrassed. (Whether or not we enjoy that type of film largely depends on how comfortable we are with cringing ourselves; I'm more the hide-under-the-cushions type.) Part of this is explained by the fact that embarrassment is also occasionally embarrassing to witness: rather than being satisfied that a person is showing shame for doing something silly, we ourselves feel acutely prone to blush and feel uncomfortable. As Professor William Miller wrote in 1994,

"The manifest embarrassment of another also embarrasses others who witness it. Blushes produce blushes because embarrassment makes demands on our tact which we are not always up to. Do we pretend not to notice? Do we notice and say something to defuse the situation?"

He pointed out that the mutual embarrassment (which can also "feed on itself", as the first embarrassed person gets more uncomfortable noting that others are now embarrassed too) makes everybody "a community of equals again," "restoring smoothness to a disturbed social setting." Obviously this has exactly zero effect if the person is on the other side of a movie screen.

Open signals of embarrassment, which are pretty easily detectable by other humans, actually serve an excellent social function. A 2012 study, for example, showed that when people showed embarrassment, those in their vicinity were more likely to see it as a signal of the person's "commitment to social relations," and were more likely to see them as trustworthy. We tend to view it as a "nonverbal apology," and the more obvious it is, the better.

Research published back in 2009 in the journal Emotion backs up this view. We don't keep embarrassment to ourselves, according to the scientists behind the study, because it's much more helpful to show it, whether we blush, avert our gazes, or show other signs of acute self-shame. It's not something we can necessarily control, so it's also trustworthy as a sign to other people. And that, the scientists wrote, can "mitigate the negative social impression that was caused by the infraction." Obvious embarrassment, and the fact that it's singularly unpleasant, can take the place of punishment from others, and also seems to make them like the embarrassed person more.

The moral? If you've f*cked up socially, it's a good idea not to attempt to hide your reaction to it. Blush and stammer; it makes people like and trust you, rather than perceiving you as an over-confident ass.