Humans can identify sick people by looks alone

A new study shows that humans are able to tell if someone is sick just by looking at their face.

Joseph Scalise | Jan 05, 2018

A team of international researchers have discovered that humans can detect if someone is sick just by looking at them, according to new research published in the Proceedings of the Royal Society B

In the study, scientists gave 16 healthy volunteers between the ages of 19 and 34 a shot of lipopolysaccharides (LPS) -- a sterile molecule taken from bacteria that can induce flu-like symptoms for a short period of time.After the injection, some of the participants became sick, while others did not feel any symptoms at all. The researchers then took photos of all of the patients roughly two hours after they administered the shot.

Then, on a different day, the same 16 subjects were given a placebo that came with no symptoms. After more photos were taken, researchers gave the two sets of images to 62 neutral observers to see if they could tell when the subjects were sick and when they were healthy. They tested that by asking the observers to rate every picture on a scale of how sick they thought the person was when the picture was taken.

The team collected 2,945 ratings for the 32 different photos, and the data showed that the observers noted 41 percent of the images as sick. As 50 percent of the photos were of sick people, that means the observers were right 775 times and wrong 440 times.

In addition, the observers managed to accurately distinguish the sick and healthy pictures for 13 out of the 16 subjects. That meant there were stark differences in those 13 patients. The high success rate meant the correct guesses were not by chance.

"We can detect subtle cues related to the skin, eyes and mouth," said lead author JohnAxelsson, a researcher atthe Karolinska Institute, according to The Washington Post. "And we judge people as sick by those cues."

This study shows that humans have an innate ability to detect signs of illness in an early phase after exposure to infectious stimuli. While most of the cues -- including paler lips and skin, a more swollen face, droopier mouth corners and eyelids, and redder eyes -- were fairly obvious, the research could help both doctors and computer software better detect sick people. That could then lead to better diagnostic tools in the future.

Though researchers are not sure, they believe this ability developed as a way to keep people healthy. If humans are able to recognize someone as sick, they can they stay away and limit their exposure to disease.

"An ability to detect sick people would allow people to avoid being close to sick people, and hence minimise the risk of becoming sick if the person is a carrier of contagious disease," added Axelsson, according toInternational Business Times.

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