Ah-choo! Healthy sneezes, coughs sound just like sick ones to us

There may be subtle differences in the sounds, but the human ear can’t detect them

A lot of conditions can trigger a sneeze or cough, from allergies and infections to just inhaling a whiff of irritating dust. A new study finds that people can’t tell when the person who coughs is sick or healthy.

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As you’re walking down the street, someone coming your way lets out a nasty cough. “That person sounds really sick,” you think. You veer far to the side to distance yourself. But a new study suggests your ear may have gotten it wrong. People can’t hear the difference between the cough of someone with an infection and someone who has just a tickle in their throat.

Scientists shared their finding June 10 in Proceedings of the Royal Society B.

The body’s immune system can fight off infections. But it can take a lot of energy to do that, notes Nick Michalak. What’s more, it sometimes falls short, observes this social psychologist. He works at the University of Michigan in Ann Arbor. That’s why, he says, “many organisms, including humans, have developed . . . behaviors to prevent pathogens from [causing infection] in the first place.” Among these: being grossed out by possibly infectious materials, such as feces and snot.

Earlier studies have shown that people can sometimes gauge whether someone is sick with an infection by sight or smell, Michalak says. Using sound, however, remained largely unexplored.

So he and his colleagues recruited several hundred people for a series of small studies. Researchers played short audio clips for participants of coughing and sneezing. The sounds came from more than 200 sick and healthy people. All had appeared in videos on YouTube.

The studies’ participants were asked to judge each cough or sneeze on whether it had come from someone who was ill or not. When the testing was over, many recruits said they had been confident they heard a true difference between sick and healthy coughs and sneezes. In fact, their judgments were no better than a coin toss. They were equally likely to hear a healthy person as sick as not. Similarly, they were as likely to hear the cough of an infected person as coming from someone who was healthy.

Earlier sound-based research has turned up actual differences between sick and healthy coughs, Michalak notes. His work now suggests the human ear can’t pick up on what makes them different. Or perhaps people need to integrate how someone sounds together with other data, such whether a person looks healthy.

During the global COVID-19 pandemic, many people are on high alert to avoid becoming infected. Michalak says that his team’s new studies should give people pause before jumping to conclusions about whether someone is sick based on a cough or sneeze.

Jonathan Lambert is the staff writer for biological sciences, covering everything from the origin of species to microbial ecology. He has a master’s degree in evolutionary biology from Cornell University.

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