When your immune system meddles in your love life

About a decade ago, evolutionary psychologists suggested that humans have evolved a first line of defense against disease: a behavioural immune system (BIS). This system is thought to be unconsciously activated, to varying degrees, when an individual perceives, rightly or wrongly, that there is a threat of disease. Although we cannot see microorganisms with our naked eye, we are nevertheless able to identify cues (such as coughs, unpleasant smells or skin lesions) which hint at the possible presence of pathogens, whether or not these are actually present or represent real health threats. Scientists have suggested that the activation of the BIS leads to prejudiced and avoidant attitudes and behaviour towards those who display superficial cues connoting disease.

But how does this affect our dating lives, where two competing needs are pitted against one another – i.e. the potential benefits of connecting and finding a mate versus the need to protect oneself from disease? McGill scientists set out to find out, by looking at the activation of the BIS in young, single, heterosexual Montrealers in both real speed dating events and in experimental online dating.

The results were convincing. And not so happy.

“We found that when the behavioural immune system was activated it seemed to put the brakes on our drive to connect with our peers socially,” said Natsumi Sawada, who holds a Ph.D. in Psychology from McGill University and is the first author on the study which was recently published in Personality and Social Psychology Bulletin.

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