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It’s that time of year when it seems that everyone is coughing, sneezing or complaining of a sore throat. Fortunately you have a brain that is ready to protect you.
A new study published in the journal Proceedings of the Royal Society B shows that people are incredibly good at judging whether someone is suffering from an illness just from a single look at them.
The human sixth sense
This heightened ability to detect infection is known as the “behavioral immune system.” It is a kind of “sixth sense” acquired at some point during evolution to reduce your chances of contracting a contagious disease.
“The ability to detect illness would allow people to avoid spending time near sick individuals, thereby minimizing the risk of infection if that person is a carrier of a pathogen,” John Axelsson of Stockholm University, a co-author of the study, told AFP.
The team of Swedish scientists tested this by creating two sets of photographs of 16 healthy volunteers.
They first gave the team an injection of lipopolysaccharide, which is a molecule found in certain pathogenic bacteria that causes a strong immune response in animals.
The molecules are sterile, so it was not possible for the subjects to actually become ill. After two hours they photographed them. In that time their immune system had been activated and essentially caused them to appear sick.
At the second photographing the volunteers were, without their knowledge, given an injected placebo, so they were in fact completely healthy.
These two sets of photographs were shown to 62 other participants to determine whether they saw any difference in the same person.
People can tell that someone is sick just by looking at their face
Fig. Can you recognize which person is ill? The face on the left belongs to the person who is sick, the face on the right to the person who is healthy. Audrey Henderson / St. Andrews University
How the test results turned out
Observers were able to correctly identify the sick-looking person in 81% of cases.
The best indicators of illness turned out to be pale skin, droopy eyelids, pale lips and red eyes.
“This supports the theory that people have the ability to detect signs of illness in the early phase after exposure to an infectious stimulus.
It would be especially useful for identifying sick individuals in the early stages of illness when the risk of transmission is high,” the authors wrote in their study.
Conclusion
This surprising human ability to find cues in faces that help recognize illness has actually not been much studied before.
We are, however, all quite good at avoiding disease, under the idea that our feeling of disgust protects us from getting sick.
For example, a dirty oven would probably make you turn your face away and move in another direction, since it could potentially contain harmful pathogens.
As emphasized in this study, as people we may be even more skilled at avoiding disease than we currently realize.
