By Karen Kaplan
Los Angeles Times
WWR Article Summary (tl;dr) Can you tell if someone is sick just by looking at their face? A new study suggests that is the case. Study authors say this capability has a clear evolutionary purpose.
Los Angeles Times
People can judge whether someone is sick by looking at a photo for just a few seconds.
That may not sound remarkable, until you consider that the sick people in the photos were in the very early stages of illnesses.
They were participants in a scientific experiment and had agreed to be infected with a bacterium that would cause an inflammatory response. Their portraits were taken just two hours after infection.
Those pictures, along with portraits of the same people taken when they were healthy, were flashed in front of dozens of study volunteers in random order. The volunteers had no more than 5 seconds to guess whether the person in the picture was sick or healthy.
In the first series of ratings, 62 volunteers made 2,945 judgments about 32 pictures (of eight men and eight women, each photographed after being injected with an E. coli endotoxin and after being injected with a placebo).
The volunteers guessed that 1,215 of those pictures were of people who were sick. Those guesses were correct 64 percent of the time and incorrect 36 percent of the time, according to a study published this week in the Proceedings of the Royal Society B.
Apparently, three of the 16 participants were particularly inscrutable; when they were removed from the analysis, the volunteers guessed right 81 percent of the time, the study authors found.
On a scale on which 0.5 means guessing at random and 1 means guessing right every time, the volunteers scored a 0.62. In other words, they did significantly better than if they had just flipped a coin to decide whether someone was healthy or sick.