The perception of disease helps us avoid becoming sick. Image: Robert Kneschke/Shutterstock
The behavioural immune system acts as a smoke detector by signalling the body to prepare for disease.
Often when we are around sick people we start to feel sick ourselves — think, for example, of catching public transport in winter when everyone around you is coughing and sneezing. All you can think about are those tiny little virus and bacteria cells hovering around in the air trying to find their way into your nostrils. According to a new study conducted by researchers from Florida State University, this is your behavioural immune system at work, responding to disease threats to help you avoid becoming sick.
“Our mind evolved to help us avoid contracting diseases”“not by being accurate in our perceptions of the world but by being biased toward making safe decisions,” explained Saul Miller, lead author of the study published in the Journal of Personality and Social Psychology. “That is, our mind is like a smoke detector.”
Throughout our species entire existence the most common challenge has been avoiding the threat of infectious disease. We now know a great deal about the physiological response of the body once disease manifest, but we know much less about how we deal with pathogens before they enter the body — that is, how we perceive them. This is the basis of Millers’ interest in the role of behavioural and psychological immunity.
Miller and his colleague, Jon Maner, conducted a study that consisted of different situations where participants would, in some way, encounter disease and be asked to make judgements.
In one experiment some participants read an article on the H1N1 flu virus, whereas another group read an article on winter storms, which was the control story. Both groups would then be shown a picture of a person and have to categorise them as being “fat” or “thin”. It has been shown in prior research that overweight people are often stereotypically associated with contagious disease. Miller explained that seeing obese individuals might be, to the behavioural immune system, like a smoke alarm accidentally going off in response to steam or dust.
“What we found is that participants who read an article about H1N1 were more likely to mistakenly categorise pictures of thin individuals as fat than participants who read a control article,” said Miller. “In other words, concerns about disease led people to perceive disease threats when none existed.”
The study not only shows the behavioural immune system in action, but it also highlights a type of prejudice when associating certain people with disease. Not only overweight people were more likely to be associated with carrying contagious diseases, but the processes also applied to elderly people and foreigners. This type of health discrimination has led Miller into his next area of research looking at whether disease concerns actually lead people to exclude certain types of people (i.e. obese, elderly) from the community.
“Perceiving them [stereotyped individuals] as not belonging to the group may be a first step toward social exclusion,” said Miller. “Therefore, understanding this process is very important for understanding the roots of discrimination and prejudice.”
