Consider the scenario:

Imagine you’re sharing close quarters with another person during a serious flu outbreak. Public health officials have urged people to be cautious about spreading the infection that’s making people extremely sick, but you don’t know whether this person has the flu or not. They may not even know themselves. 

Which of your five senses would you be likely to use to determine whether this companion is sick? Would you watch and listen for sniffles? Would you touch the other person, or lean in to detect an odor? Which senses do you think would be most useful for gauging your safety?

Psychology of Germs

Josh Ackerman, a professor of psychology and an affiliate of the Research Center for Group Dynamics at the University of Michigan Institute for Social Research, 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,” said Ackerman. “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.”

When prompted to imagine the scenario above, Ackerman’s past research has shown that most Americans use and trust their senses for detecting sick people very consistently. 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, we 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 close proximity with other people when it comes to infectious disease.

Universal Beliefs

But are those sensibilities universal?

A new study out in Brain, Behavior, and Immunity, led by Ackerman along with over 100 collaborators, 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,” said Ackerman. “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.”

Findings from the new study, which spanned 62 countries representing all world regions and a third of the globe, showed beliefs about the sensory detection of infectious disease are strikingly consistent across cultures.

The researchers found 95% concordance in how respondents ranked the effectiveness of each sense, and 97% concordance in how they ranked their likeliness to use each sense– indicating near-perfect agreement.

Explaining Variance and Consistency

In the few cases where variation occurred, it was predominately between rankings of hearing and touch. Respondents in countries that were lower in latitude, less prosperous, and carried higher disease burden drew fewer distinctions between these two senses. We 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 we hold have been effective over time at keeping us alive. 

This doesn’t necessarily mean that we can trust our senses to identify hazards accurately, Ackerman said. His previous research found that people are not so 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.

Josh Ackerman’s research explores how exposure to contagious disease cues and bodily factors such as immune system functioning interact to influence various forms of social behavior. In addition to his affiliations with Psychology and the Research Center for Group Dynamics, Ackerman is a Professor of Marketing at the Stephen M. Ross School of Business.

This post was written by Tevah Platt, communications manager for the Research Center for Group Dynamics.