At the moment, most of us are on red alert when it comes to sounds of illness, with sniffling in the supermarket or coughing behind us in a queue the cause of significant alarm.
And while we might like to think we’re able to tell the difference between someone clearing their throat and somebody who is genuinely unwell, new research published in Proceedings of the Royal Society B suggests we’re less good at identifying threats than we think.
To investigate how well people can detect pathogen threats from cough and sneeze sounds, Nicholas M. Michalak from the University of Michigan and colleagues first recruited 148 participants to listen to 20 audio clips of coughs and sneezes taken from online videos. Half of these sounds were from people who were genuinely ill with colds or the flu, whilst the other half merely had allergies or had consumed powdery spices and were therefore non-infectious.
After each clip, participants indicated whether they thought the sound was from someone with an infectious or non-infectious condition, and were also asked how certain they were about their answer. Finally, they completed an index of disease concern, which measures worries about contracting certain illnesses.
But participants were no better than chance at correctly identifying infectious and non-infectious coughs and sneezes, with 45% accuracy across the board and no difference when it came to each type of sound. Participants were reasonably certain about their judgments — but, in fact, for those who were more certain were actually less accurate.
A second study looked at the impact of disgust on identification of infectious sounds. The team played the same sounds to 146 participants — only this time, in addition to identifying the sounds, participants were also asked how disgusting they found them. Again, participants were no better than chance (42%) at detecting infectious or non-infectious coughs and sneezes, and increased certainty was related to decreased accuracy. Disgust did have an impact, however: the more disgusting participants found a cough or sneeze, the more likely they were to judge it as having an infectious origin, regardless of whether it was actually infectious or not. A third study replicated these findings.
So it seems as if we’re more likely to perceive something as a threat if we find it more disgusting — but that that assumption fails to serve us in terms of accuracy. This may be a protective measure: it’s probably safer, in the long run, to presume something innocent is actually infectious.
The experiments here only contained audio, and the team notes that people may be much better at identifying infectious sounds when integrated with other sensory information — if somebody sneezes and also has a hoarse voice and bags under their eyes, we’re probably going to know they’re ill; if they’re holding a spoon full of cinnamon ready to do a viral challenge, they’re probably not.
Telling the difference between an innocent and infectious cough feels like a useful thing to be able to do, particularly considering the current situation. But, as this research shows, we’re not actually very good at it. “Thus, the next time you hear someone cough or a sneeze”, the team concludes, “perhaps leave the diagnosis to the doctor.”