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Coronavirus Disease 2019

Boosting Our “Behavioral Immune System” to Beat COVID-19

Let's stop the virus from fiendishly targeting our “behavioral immune system.”

An April 2020 article about COVID-19 by Wadman et al in the online version of the prestigious journal Science observed “…a clear picture is elusive, as the virus acts like no pathogen humanity has ever seen.”

Although the 3 months of experience with COVID-19 since the April article in Science have not brought us a complete picture of how the virus works, one feature of the pathogen is coming into sharper focus: COVID-19 seems to kill many of its victims by triggering a devastating inflammatory overreaction of the immune system, particularly in the lungs.

In effect, the virus may trick our bodies into destroying themselves.

That’s the bad news.

The good news is that we have a second immune system-- what Mark Schaller of the University of British Columbia calls our “behavioral immune system”-- that can stop our biological immune system from killing us …by preventing us from contracting the disease in the first place.

According to Dr. Schaller, humans have evolved a number of behaviors that reduce the spread of pathogens such as COVID-19. These behaviors include avoiding individuals that look ‘ill” and experiencing feelings of “disgust” at pathogen-carrying substances such as feces, mucous and vomit. And individuals who are ill with an infection, for their part, reduce their activities and social interactions, lowering the chance that they will infect friends and family. Collectively, such behaviors constitute a “behavioral immune system” that strives to keep a newly introduced pathogen from ravaging a group.

It turns out that humans are not unique in exhibiting behavioral immunity: social lobsters, tadpoles and monkeys also avoid sick members of their community. A recent New York Times article showed that even vampire bats self-isolate when sick.

Today’s stay-at-home orders, business shutdowns, social distancing guidelines and masks are all examples the human “behavioral immune system” at work, but the recent surge in infections, hospitalizations and deaths point to a breakdown of this immune system.

And I believe the peculiar nature of COVID-19 is directly contributing to this breakdown.

Three ways COVID-19 breaks down behavioral immunity

First, the majority of infected people show mild symptoms--or no symptoms at all—so most of the population has no direct experience of harsh, sometimes lethal affect the disease can have on its victims. That’s why I’ve started to see many of my contacts on social media pose the question “Do you personally know anyone who’s been infected or has died of coronavirus?” strongly inlying the “so-called pandemic” is a “tempest in a teacup.” Most people suffer few direct consequences -at least for now-- so they doubt its lethality and relax their “behavioral immune system”, refusing to wear masks or socially distance themselves. Unacast, who monitors social distancing through geo-location data from multiple cell phones of people in public settings has shown just how widespread the lack of social distancing is in the U.S. giving 35 states a grade of “F” and the remainder a grade of “D: for social distancing (judged by distance between multiple cell phones).

Second, the virus targets what behavioral economists call “temporal myopia” or “hyperbolic discounting,” cognitive biases that heavily weight near term benefits against future costs. Put another way, to the human brain, and inch of “now” is worth a mile of “later.” Thus, to people already skeptical of COVID-19’s lethality, inconvenience of masks and social distancing are not worth bearing NOW in order to avoid an improbable problem LATER, especially when the people we’re supposed to avoid NOW show no here-and-now symptoms to stimulate instinctive disgust or avoidance reactions. The relatively long incubation period of COVID-19 (sometimes as long as 2 weeks) makes temporal myopia even more problematic in the current pandemic.

Finally, COVID-19 is enjoying spectacular success today by stimulating one part of the human behavioral immune system to attack another part of the same behavioral immune system.

Here’s what I mean by this perverse, “auto-immune” damage caused by the virus.

Evolutionary psychologists theorize that one reason we evolved tribal, xenophobic, even racist tendencies, is to minimize contacts with humans that might carry unfamiliar pathogens to which our immune systems have not developed immunity (Native Americans, for instance, were ravaged by small pox from Europeans because their immune systems were unfamiliar with it).

According to this theory, during pandemics, people can be expected to become even more tribal, which, I would argue, is exactly what we are experiencing with the politicization of masks and other behavioral measures to slow the spread of COVID-19, such as school closures.

For the purpose of this discussion, I will define “tribes” not as racial, ethnic, geographic or religious groups, but as groups with opposing ideologies.

I think members of one one ideological “tribe”— I’ll oversimplify and call it the “individualist tribe”-- are building up the instinctive boundaries that “protect them” from other tribes, particularly what I’ll call “the collectivist tribe,” by strongly adhering to individualistic cultural norms, such as self-determination and a extreme distaste for government intervention.

At the same time, many members of this “individualist tribe” look with scorn on beliefs and practices of the “collectivist tribe” (who believe the needs of the many outweigh the needs of the few), and who are strong advocates of measures that will protect the population as a whole, such as masks, social distancing and shut-downs.

If I’m right that COVID-19 has energized parochial instincts to the point many people won’t embrace masks or other important defenses against COVID-19, then the virus has, paradoxically, co-opted one of the very behaviors –tribalism--that evolved to defeat it

Sound familiar?

COVID-19’s modus operandi seems to be the same whether co-opting our biological immune system or behavioral immune system: the virus doesn’t directly kill us, but manages to get us to kill ourselves.

So what’s to be done?

Well, those of us who find themselves—if only temporarily --in the “collectivist” ideological tribe can try to marshal arguments based on biology, epidemiology, evolution and statistics to change deeply ingrained beliefs and values of the other tribe… or… we can imitate social lobsters and simply steer clear of any and all members of our species who could make us sick.

I wish you luck taking the first path using science, data and logic, but having tried and failed miserably at that with my ”individualist” friends, I’m closely following the path of social lobsters.


Schaller, M., and Park, J. H. (2011). The behavioral immune system (and Why It Matters). Curr. Dir. Psychol. Sci. 20, 99–103. doi: 10.1177/0963721411402596…

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