If you're sharing close quarters with someone during flu season, how would you know they are sick, even in cases where they may not know themselves?
A new global study led by a University of Michigan researcher found that people worldwide-when choosing among their five senses-agree that sight and hearing are the most useful senses, followed by touch, smell and taste.
From the analysis involving more than 19,000 people from 58 countries, some differences were found based on factors such as the country's level of development and population density-but generally, the researchers found overwhelming agreement.
"Overall, people tended to prefer senses that minimized their own risk of getting sick," said lead author Josh Ackerman, U-M professor of psychology and an affiliate of the Research Center for Group Dynamics at the Institute for Social Research.
Ackerman is an expert on the psychology of germs. His work delivers insights into how people think about and react to the threat of pathogens, with real-world consequences.
"It's important to understand lay beliefs about how illnesses present because they can shape people's actions and behaviors in contexts where disease transmission is possible," he said.
"These beliefs also have implications for how we judge other people, groups and places that may or may not pose real danger. Believing that others pose disease threats can lead to avoidance, prejudices and support for restrictive workplace and governmental policies."
Ackerman's past research has shown that most Americans use and trust their senses for detecting sick people in consistent ways. They rank sight and hearing first and second-above touch, smell and last of all, taste.
Survey response patterns supported what Ackerman has proposed as a "safe senses hypothesis." That is, people may be biased to prefer using senses that function at a safe distance when assessing whether another person is sick, even if we believe that the more proximal senses, touch, taste or smell, would give us useful information.
"Where we might lean in to smell a carton of milk to detect danger, we're motivated to avoid proximity with other people when it comes to infectious disease," he said.
Universal beliefs
But are those sensibilities universal?
The new study, published in Brain, Behavior, and Immunity, examines whether these patterns are the same around the world.
"One possibility is that we might see cultural differences affecting the senses that we use and believe will be useful for detecting illness in people," Ackerman said. "Culture can influence social norms, how people think about contaminants, and even which senses we might emphasize. Alternatively, we may share common beliefs with people across cultures."
The findings showed beliefs about the sensory detection of infectious disease are strikingly consistent across cultures.
Explaining variance and consistency
In the few cases where variation occurred, it was predominantly between rankings of hearing and touch. Respondents in countries that were lower in latitude, less prosperous and carried a higher disease burden drew fewer distinctions between these two senses.
Some might speculate about factors such as education, cultural traditions or habituation to disease that might explain these outliers, Ackerman said, but the variation detected in the study paled in comparison to the cross-cultural uniformity of beliefs that they observed.
"It may be the case that the world holds consistent ideas about sensing disease because hazards present themselves similarly across human groups, and because the beliefs people hold have been effective over time at keeping us alive," he said. "But this doesn't necessarily mean that we can trust our senses to identify hazards accurately.
Ackerman's previous research found that people are not good at detecting sick people by the sound of their sneezes and coughs. Instead, it may be that being biased to believe that all "disgusting" sounds signal danger is useful and adaptive, since the cost of missing infection threats may be higher than the cost of false alarms. Relying on our socially distanced "safe senses," too, may be a shared bias that works for us by preventing the spread of infection, he added.
Written by Tevah Platt, Institute for Social Research
