Why do we smile and even giggle when we're afraid? Are we trying to work things out? Or are we trying to convince everyone, even our attacker, that nothing's wrong? Here's what science has to say about "fear grinning."
One of the more ghastly human responses is the "fear grin." I automatically sink into it when things get socially awkward. Whenever people start sniping at their spouses or arguing who has to pay what on a restaurant bill, I lapse into a blank-eyed smile that implies that I'm just there to do a little dusting, and the dispute has nothing to do with me. But plenty of people smile to cover an awkward situation. They shouldn't smile when they're being mugged. Dial up the extremity of a situation, and fear should eliminate the smile, but some people, even when terrified, smile away. Why they do this is in dispute, but there are two general theories.
Acknowledging the Fear
A dog baring its teeth is showing aggression. It's displaying its weapons. Monkeys, when they show off their teeth, aren't necessarily doing the same. Primatologist Signe Preuschoft studied rhesus macaques, and noticed a great deal of teeth-baring in their social interactions. It did not signal the beginning of a fight. Most often, it happened during moments of tension between more dominant and less dominant members of a group. The less dominant monkey was the one that smiled, and often, after the smile, the aggressor became more friendly. The macaques weren't showing off weapons. They were making a sort of display of submission to the more dominant member. When danger threatened, they smiled. This behavior has come to be called fear grinning.
Preuschoft noted that the smile wasn't just used during crises. During friendly everyday activities, the monkeys smiled at each other readily enough. Humans, it seems, took that smile and adapted it to express approval, joy, compassion, or sympathy - they made it into a more expressive form of communication. But when we recognize a dangerous situation, a smile can still come out. We notice someone is dangerous, and try to appease them.
Denying the Fear
There is another possible reason for our frightened smiles. Perhaps we don't acknowledge the fact that we're in danger. Perhaps we deny strenuously that there's danger at all. The famous Milgram experiment made volunteers believe that they were giving painful - and sometimes fatal - electric shocks to an unseen fellow volunteer. The volunteers were pressured into it by an authority figure in a lab coat. As the shocks increased, and as the screams from the fellow volunteer got louder, many of the subjects began to laugh nervously. They weren't having a good time, but they didn't know how to protest other than laugh. Another experiment, in which volunteers were made to behead a mouse while their faces were photographed, produced ghoulish photos of people giving pained smiles as they were forced to do something they didn't want to do.
V.S. Ramachandran, a neuroscientist, believed that laughter was a kind of signal to those around the laugher. Although a situation might seem frightening or threatening, the laughter might give surrounding people the all-clear. When we laugh under direct threat, or threat to the people around us, we might be denying that there's a danger at all. We might be trying convince the aggressor that everything will be all right.
Why Do We Do It?
So why do we begin to smile, or laugh nervously, when we feel fear or uneasiness? If we look at our evolutionary history, we start smiling because we recognize that we're in a dangerous situation, and we want to signal the person who is dangerous that we have no wish for escalation. We are openly acknowledging fear. On the other hand, if we look at the work of psychologists and neuroscientists, we're denying danger so strenuously that we hope even the source of that danger will be fooled.
It could be something more basic. The book Laughing Screaming looks at the connection between the famous "low art" genres of gross-out comedy and schlock horror. The two are linked, according to author by the fact that, unlike almost any other movie, they attempt to evoke a bodily response from the viewer. We've seen that, under the right circumstances, weeping can sound like laughter and joy can look like fear. Perhaps there is just a limited number of physical responses that can be automatically produced via our emotional state, and it is only context that can make a grimace or a convulsion look positive or negative.