Why smiles, frowns and grimaces are contagious

Humanity’s ability to read and understand facial expressions has been hardwired into our ancient brains. A recent review published in Trends in Cognitive Sciences looks in depth at this marvelous ability to display, share and generate emotions.

We are all experts at deciphering the complex movements of muscles in other people’s faces.

In the depths of time, when faced with a stranger, there was a clear benefit to any human able to understand the newcomer’s motives.

Was the individual angry? Could he be looking for trouble? Does he need help?

Life or death might genuinely depend on a split-second decision about the state of an outsider’s facial features.

Today, although meeting a stranger is much less likely to end in our demise, being able to read people’s feelings is still incredibly important.

Modern society is wildly complex; the number of faces we are all presented with on a daily basis has risen exponentially over the last few centuries.

Quickly rating and understanding a partner, colleague or family member’s facial expression is essential to maintaining relationships, jobs and the status quo.

Paula Niedenthal and Adrienne Wood, from the University of Wisconsin, released a paper this week that explores the current state of knowledge in regards to facial expressions and their mimicry.

The sensorimotor simulation model
The paper focuses primarily on the sensorimotor simulation model of emotion perception. This model predicts that when we observe a certain expression, be it happy or sad, we momentarily “try it out.”

This is why, if someone is smiling, it can be contagious. This “trying out” helps us to associate their emotional experience with a time in the past when we have felt a similar emotion. By charging up the same parts of the brain and similar muscle groups, we jog our memories and enable empathy.

The authors say:

“You reflect on your emotional feelings, and then you generate some sort of recognition judgment, and the most important thing that results is that you take the appropriate action – you approach the person, or you avoid the person.”

Sometimes, this sensorimotor simulation will not make it from the brain to the facial muscles, or only in a diluted form. Rather than a full smile, perhaps only the corners of the mouth will turn up, for instance.
However, the appropriate parts of the brain – the somatosensory and motor systems – that are involved in making the emotion-specific facial movements are still activated. The brain recreates the expression internally without charging the facial muscles with the job of actually producing it.

Our facial expressions are very much a two-way street. When we feel happy or angry, our faces display these feelings. That is no surprise to anyone, but what is more surprising is that a forced smile can actually induce happiness where there was none before.

Experiments where participants are put in an uncomfortable situation and forced to smile have demonstrated that the perceived negativity of the experience is reduced by the act of smiling. Other studies, using depressed patients, have found that by paralyzing the muscles responsible for frowning, depressive symptoms can be reduced.

Our emotions produce our facial expressions, but our facial expressions can also produce our emotions.

Similarly, a study was carried out on patients with facial paralysis. The level of depression they experienced could be predicted by the degree to which the muscles involved in smiling were paralyzed. In other words, their ability to display a smile, or lack thereof, affected their emotional state.

When mimicking is not possible
The importance of facial mimicry becomes particularly obvious in research using individuals who do not have this ability. For instance, those with motor diseases, like stroke or facial paralysis. These people can have difficulty sharing in other people’s emotions. The door to people’s feelings has been partially closed.

Another disorder that famously includes a lack of insight into other’s emotional states is autism. The authors say:

“There are some symptoms in autism where lack of facial mimicry may in part be due to suppression of eye contact.”

They go on to say that “if you encourage eye contact, the benefit is spontaneous or automatic facial mimicry.”

Niedenthal and her colleagues plan to further investigate sensorimotor simulation and its role in human emotions and empathy. They hope that their discoveries might shed some light on disorders where facial mimicry is challenging.

Medical News Today recently covered research that used a robot baby to investigate the motives of an infant’s smile.