A little over a decade ago, Mark Schaller, who is a psychological scientist at the University of British Columbia in Canada, suggested that in our daily interactions with the world, our minds are very good at automatically picking up subtle signs of disease, such as a person coughing or sneezing.
This, he argued, sends an alarm signal telling us to avoid the potential source of contamination, so, almost without thinking, we do our best to stay away from the person who we perceive — wrongly or rightly — as contagious.
Schaller coined the term "behavioral immune system" to refer to this defense mechanism, which he deemed to be our most basic form of defense against disease.
In an article that was published in 2011, he explains that to fight environmental pathogens after they have entered the body, our systems have "evolved sophisticated physiological mechanisms (the immune system)."
"But," he adds, "it can be costly to actually mount an immune response. Therefore, [...] an additional set of mechanisms [evolved] that serves as a crude first line of defense against pathogens — what can be called a behavioral immune system."
"These mechanisms detect the presence of pathogens in the immediate environment and facilitate the avoidance of those pathogens before they make contact with the body."
Behavioral immune system always alert
It makes sense for this behavioral defense mechanism to kick in when we are on our commute to and from work or in the office, so we can stay out of harm's way and preserve our health.
But what happens when we are looking to forge an intimate, romantic connection with someone? Will our behavioral immune system trigger automatically when it is faced with the subtlest sign of disease, despite the fact that forming a good romantic relationship can have such high stakes for emotional well-being and reproduction?
This is the question that researcher Natsumi Sawada and colleagues from McGill University in Montreal, Canada, recently asked themselves and set out to answer.
To do so, the reseachers conducted three separate studies with three sets of participants. The first two studies tested whether individuals were likely to express avoidant behavior toward peers who they perceived as presenting potential threats to their own health in different social situations.
"Studies one and two demonstrated that participants' chronic level of [behavioral immune system] activation [...] was associated with decreased affiliative interest in two different social situations," the researchers note in the paper that they recently published in the Personality and Social Psychology Bulletin.
Following these results, in the third study, the team decided to manipulate the participants' level of wariness regarding the potential for contagion before sending them on a blind date simulation experience.
To this purpose, Sawada and colleagues worked with 154 participants aged under 25 — all of them single and seeking, heterosexual, college undergraduates, and all of whom were based in Montreal.
Fear of disease 'may influence' connection
First, Sawada and her team "primed" the participants' psychological responses by showing them a video about disease and contagion. Then, they showed each participant more videos, in which a person of the opposite sex acted as a potential partner in a blind date. Finally, the participants recorded their first impressions of the people they had thus "met."
"We found that when the behavioral immune system was activated it seemed to put the brakes on our drive to connect with our peers socially," Sawada notes.
However, she adds that these findings were by no means expected — to the contrary, in fact. The researchers were rather surprised to learn that our behavioral immune system remains so alert even in situations when we are motivated to seek closeness and connection.
"We hadn't expected this to be the case in real-life situations like dating where people are generally so motivated to connect," says Sawada.
"The results," she argues, "suggest that beyond how we consciously or unconsciously think and feel about each other there are additional factors that we may not be consciously aware of, such as a fear of disease that may influence how we connect with others."
Below, you can watch a short video explaining the premises of Sawada and team's study.