The salacious comment from a colleague, the mustard stain on our shirt, or when our parents candidly tell us that we wet our diapers until we were four: most of us blush when we are embarrassed or ashamed - and they can't do anything about it. Worse still: the blush is not only caused by embarrassing situations, but makes the whole thing even more embarrassing.
Scientists have tried to find out what the reddening of the face is all about and why this effect has prevailed in evolution in the first place. Because that's no use to anyone, is it? The result of an American study: The red face is extremely helpful for interpersonal communication.
The starting point of the researchers led by Chris Thorstenson from the Institute of Technology in Rochester is the fact that the flushing caused by dilated blood vessels in the skin cannot be controlled at will. "It's difficult, if not impossible, to make ourselves blush and make that blush go away," Thorstenson explains. Which ultimately means: those who have blushed with shame don't lie, because they can't hide it.
This can be helpful for a cooperative society. The blush would thus be a communication signal that has prevailed in evolution to ensure more transparency and honesty in human interaction.
To substantiate this thesis, the US researchers confronted their subjects - all students at Rochester University - with photos of faces that allegedly belonged to people who had been caught lying. However, they were presented in different colors, ranging from neutral paleness to deep red. It turned out that people with blushing faces were rated as more sincere, embarrassing, and forgivable, regardless of whether you viewed all the images individually or the Faces with the different colors had shown at the same time.
This means that someone caught lying can hope for forgiveness if they only blush really hard. The blush is interpreted as an expression of sincere concern.
Apparently, the phenomenon does not only work in connection with embarrassment. When the research team presented the subjects with a series of photos showing other emotional cues, such as a skeptical frown or anger, the blush had the same effect: it increased the participants' sense of the person's sincerity. And it increased their willingness to forgive the person concerned. A bright red raging choleric can also hope that his tantrums will be allowed.
Other involuntary bodily signals also determine how people are assessed by others. The researchers showed their subjects the profile photos of people who were said to be on the verge of crying. They were also shown in different colors. However, the researchers dug particularly deep into the color box, in addition to red, yellow, green and blue were also used. The result: In the case of red and yellow, the test persons spoke more of tears of joy, while tearful faces with a blue and green tinge were interpreted more as an expression of sadness.
Faces red with anger and shame therefore make an important contribution to recognizing and assessing emotions. But it is doubtful whether this - in the narrower sense of evolution - also contributed to the survival of the species. Because dark-skinned people also turn red, but you can hardly see it in them - and yet they are by no means extinct. Maybe it's just an exquisite gimmick of evolution. Not for nothing did Mark Twain say: “Humans are the only creature that can blush. Or should.”
However, tears in particular are not always easy to read for the other person. It is clear that only humans know how to cry emotionally when there are negative stimuli such as pain or sadness. As the Dutch behavioral researcher Asmir Gračanin found out, it serves to reduce psychological tension on the one hand – but also to communicate: tears signal helplessness, pain or fear. This is intended to motivate other people to support the cause.
It becomes more complicated with tears of joy or emotion. Although they are supposed to restore mental balance – insofar as positive emotions can overwhelm us – they are often not properly understood by others at first. But as soon as this irritation has subsided, tears of joy and emotion even tempt you to cry along.
But do other involuntary bodily signals also convey a message to the other person? There has been speculation that hiccups are more than an arrhythmic contraction of the diaphragm. It has been speculated that it could be an expression of nervousness. In fact, the explanation is more banal: when we hiccup, we resemble amphibians that have to spontaneously close their lungs in order to breathe underwater. When we drink or eat too quickly, this mechanism kicks in spontaneously. One could therefore speak of a relic from the early days of our evolution, which, however, no longer conveys any message in the here-and-now. According to a US study, drinking from an extra narrow straw helps against hiccups. This makes it harder to aspirate the fluid, so the phrenic nerve is busy and sort of forgets about the hiccups.
Coughing during a concert or a theater performance is also embarrassing. The economist Andreas Wagener has calculated that in theaters and concert halls people cough and clear their throats about twice as much as in normal everyday life. Melanie Wald-Fuhrmann from the Max Planck Institute for Empirical Aesthetics believes she has found an explanation for this: the suppressed urge to move forces us to cough. A compensation reaction. The economist Wagner, on the other hand, expresses a different theory. He has observed that the more unfamiliar and complicated the music becomes, the louder the cough becomes. So it could actually be a compensatory reaction, but not so much because we have to sit still, but more in the sense of a reaction to being overwhelmed. However, this phenomenon has not yet been psychologically explored.
A classic form of interpersonal communication is yawning. If a person starts to yawn, the person opposite usually does the same. An Italian study was able to show that this is due to a hormone that plays an important role in our social life: the bonding hormone oxytocin. The study measured the yawning frequency of pregnant women who have a particularly high level of oxytocin in their blood. In fact, they yawned more often than their fellow human beings, and not just because of tiredness, as study leader and evolutionary biologist Ivan Norscia from the University of Turin explains.
And what about the sneeze? Sneezing attacks often overtake us when they are unwanted. Is there also an unconscious signal to the environment behind them?
The urge to sneeze is mainly triggered by allergies and respiratory infections, 17 to 35 percent of people have to sneeze even in strong sunlight - the predisposition for this is genetic. But there are also people who have to sneeze as a result of sexual excitement. Mahmood Bhutta of Brighton and Sussex Medical School sees this as an evolutionary relic in the wiring of the autonomic nervous system. "Men and women are affected equally often," emphasizes the surgeon. The sneezing can come during and shortly after sex, or even just thinking about it. So if, in addition to the coughing, the sneezing starts in the concert hall, the musician can at least console himself with the fact that not everyone is bored.
This article was first published in October 2021.