People across cultures can tell when others are in the early stages of infection by looking at them.
Artin Arshamian at the Karolinska Institute in Sweden and his colleagues tested whether it was possible to tell if someone was sick just by looking at their face.
They worked with 169 volunteers from six different cultural backgrounds, including city-dwellers in Stockholm and hunter-gatherers in the rainforests of Thailand and Malaysia, and in the coastal deserts of Mexico. Each volunteer was shown photos of Swedish people taken two hours after they had been injected with either E. coli or a placebo.
Those who had been injected with E. coli were at the beginning stages of an immune response when their photos were taken – and some of the volunteers in all six groups had a better-than-chance ability to identify that they were sick.
The ability to tell who is sick at an early stage could benefit us by helping us decide whether to avoid certain people, says Joshua Tybur at VU University Amsterdam who was not involved in this study. “This could also be useful for people you care about, to know when they need more help,” he says.
“The most dangerous thing is if you get contact with pathogens that your immune system has little experience with,” says Arshamian. “That’s one of the problems when new populations come in and mix – they can bring pathogens to groups that have very little exposure to these and that’s really bad. Basically, this is what happened to the native Americans.”
The team had assumed that the volunteers from Stockholm would be the best at recognising sickness since the photos were of people from their own community, but this was not the case.
“I think what it means is that probably this is such a stable ability and such a general ability that cultural experience probably doesn’t affect it that much,” says Arshamian.
Journal reference: Proceedings of the Royal Society B: Biological Sciences, DOI: 10.1098/rspb.2021.0922
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