That’s Disgusting! The Behavioral Immune System
According to Charles Darwin, “extreme disgust is expressed by movements round the mouth identical with those preparatory to the act of vomiting.”
Recently disgust and its associated behaviors gained attention as an unappreciated arm of the immune system. This idea was recently explored in a paper by Steve Gangestad and Nick Grebe at the University of New Mexico: Pathogen Avoidance Within an Integrated Immune System: Multiple Components With Distinct Costs and Benefits.
Most of us take our immune systems for granted. Having an immune system allows us to interact with other individuals, the environment, and their respective microbiomes and not get sick, at least most of the time. If we encounter a dangerous microbe, the innate and adaptive arms of the immune system generally prevent invasion and disease.
Though effective, non-specific innate immune defenses and more targeted antibody-directed immunity have significant costs. These defenses are expensive both in terms of energy, friendly-fire damage to our own cells, and premature aging. It might be better for the organism to avoid pathogens in the first place.
Gangestad and Grebe are among the scientists who have shown that organisms demonstrate behaviors that decrease their contact with pathogens. These behaviors and the physiology responsible for them collectively comprise the behavioral immune system.
Behavioral adaptations involving pathogen defense, like every trait, involves both costs and benefits. These trade-offs were recently cataloged in Gangestad and Grebe’s recently published paper in Evolutionary Behavioral Sciences.
Gangestad and Grebe posited that sensitivity to disgust might be heightened in people who live dangerously, so to speak. These would be socially capable extroverts who have more interaction with other human beings. On the other hand, introverts with limited interaction with other humans might be less sensitive to disgusting stimuli, things like a bleeding cut, body odor, etc.
In line with these expectations, Gangestad and Grebe found that pathogen disgust was associated with social potency and extroversion. The authors conclude that “these findings offer provisional evidence that pathogen disgust elicited by human contaminants is more potent in individuals likely to experience higher, not lower, encounter rates with novel others.”
From the paper:
“The ideas about the behavioral immune system recently put forward have created much excitement, and for good reason. It makes perfect sense that a fully functional, adaptive immune system would not be designed to passively wait for pathogens to arrive, only to prepare for that arrival. Rather, a major function expected of an adaptive immune system is avoiding contact with potentially harmful pathogens in the first place. Specific ideas about the nature of behavioral pathogen avoidance tactics (e.g., sensitivity to disgust, withdrawal from specific social situations, ethnocentrism) have been empirically highly generative and productive.
It seems to us that the behavioral immune system should not be thought of as an entity distinct from the “classical” immune system. Neither should it be thought of in terms of a unitary trait defined in terms of “strength” of this system (cf. Terrizzi, Shook, & McDaniel, 2013). Rather, in our view, it makes sense that, just as specific tactics of and allocations to immunoresistance are multiple and regulated by sets of costs and benefits particular to each, so too might different tactics of avoidance. Allocations to specific avoidance tactics may well be adaptively regulated in concert with resistance functions (in many cases via shared physiological mechanisms) as part of an integrated immune system.”
The behavioral immune system is a phrase coined by the psychological
scientist Mark Schaller to refer to
a suite of psychological mechanisms that allow individual
organisms
to detect the
potential presence of infectious parasites or pathogens in their
immediate environment and to engage
in behaviors that prevent contact with those objects and
individuals.
The existence of a behavioral immune system has been documented across many animal species, including humans. It is theorized that the mechanisms that comprise the behavioral immune system evolved as a crude first line of defense against disease causing pathogens.
In humans and animals, activating a physiological immune response to pathogens is effective, but metabolically costly. Immune responses are activated at the expense of other fitness enhancing activities. Inflammation after infection can also be harmful to the body (e.g., contribute to diseases of aging). In addition to cultural adaptations to avoid pathogens, the behavioral immune system acts as a set of defense mechanisms to protect against pathogens before infection occurs.
Proximate Mechanisms
Mechanisms for the behavioral immune system include sensory processes through which cues connoting the presence of parasitic infections are perceived (e.g., the smell of a foul odor, the sight of pox or pustules), as well as stimulus–response systems through which these sensory cues trigger a cascade of aversive affective, cognitive, and behavioral reactions (e.g., arousal of disgust, automatic activation of cognitions that connote the threat of disease, behavioral avoidance).
Sensory Components
Smell: In humans: body odors from diseased individuals are rated less desirable and likeable, and perceived as unhealthier, more intense, and less pleasant. Disgust of body odors is also influenced by the closeness of the source of odor. Odors from family members are rated as less disgusting than body odors from strangers. Experimental studies showed that the presence of aversive odors leads to more prophylactic behaviors, such as more willing condom use and less-direct prophylactic behaviors, like stricter punishment for moral violations.
Taste: Gustatory stimuli, particularly of spoiled foods, elicit feels of disgust and motivate pathogen avoidance behavior. People with more disgust sensitivity are predicted to have more aversion to novel or foreign foods.
Sight and touch: Visual cues of pathogen threat have been linked to increases in tactile sensitivity and lead to perceived people with accents as more foreign, especially among individuals with higher disgust sensitivity. Disgust sensitivity among individuals is also predictive of preferred amount of personal space.
Overgeneralization: The “smoke detector principle” of evolved systems that regulate protective responses has also been used to describe the behavioral immune systems tendency to overgeneralize. Evolved responses to signals of pathogen threat cannot be perfect and rely on liberal identification criteria. This makes the behavioral immune system susceptible to activating when pathogens are absent.
Noninfectious physical and mental abnormalities including elderly appearance, disabilities, obesity, and disfigurement can act as cues of pathogen presence, when none are present.
Even though many false alarms may be triggered in response to these nonharmful cues, the costs associated with behavioral immune activation may be relatively small to the costs of missing a true disease threat.
Responses
Disgust
The pathogen disgust system and the behavioral immune system have been studied separately, but there is recognition that they are functionally the same. Darwin first recognized that the emotion of disgust aided in avoiding "tainted" food. The emotion of disgust has now been recognized as an adaptive function for avoiding pathogen exposure in response to cues of potential pathogen threat. However, disgust to pathogen-related cues should be context-dependent to function adaptively. In one study on the Shuar, a indigenous subsistence-based population with high-pathogen stress, pathogen disgust sensitivity (PDS), measured with a disgust questionnaire, was used to predict pathogen infection. The study found that individual PDS was negatively correlated with pathogen infection predictive of the hypothesis that disgust acts as a pathogen defense mechanism sensitive to local costs and benefits of avoidance and infection.
Functional flexibility
Functional flexibility is a term used to describe the ability of the behavioral immune system to adjust responses to pathogens depending on the individual’s infection-related threat and infection-relating vulnerability. Like many evolved threat management systems, the behavioral immune system is sensitive to the costs and benefits of pathogen avoidance.
Reactive and proactive
Two categories of outputs can be generated by the behavioral immune
system;
reactive and proactive responses
Reactive responses - occur in response to the presence of cues connoting an immediate infection risk. The responses generally take the form of avoidant or prophylactic behaviors. These can include restricted sexual attitudes, positivity towards condom use, and avoidance of people with cues associated with illness.
Proactive responses - occur in response to the long-term and
persistent threat of pathogens. Across species, proactive management
of pathogen threat can be seen
in hygiene behaviors to
mitigate reoccurring bacterial and viral threats. Additionally,
proactive responses can be seen in the importance placed on a
potential mate's physical attractiveness, symmetry, and secondary
sex-characteristics which are
all indicators of health, and
healthy people are less likely to carry disease.
Influences on Social Psychology
Two social consequences of activating the behavioral immune system according to Ackerman et al., are;
- increased aversion and avoidance of unfamiliar and outgroup targets
- strengthened cohesion with familiar and ingroup targets.
Interpersonal perception
Interpersonal perception is influenced by the behavioral immune system due to the early stage cognitive processes recruited for identifying pathogenic threat and the risks associated with interpersonal contagion.
Visual attention is one these early cognitive process recruited toward cues of pathogen threat and perceivers find it more difficult to visually disengage from faces possessing these cues, like physical abnormalities, even if no threat is present .
The behavioral immune system may also cause people who perceive greater pathogen threat to report greater distinctions between ingroup and outgroup members, and classify strangers as more threatening.
Judgment and Decision-Making
Judgments, inferences, and decisions about people and objects are other cognitive processes recruited by the behavioral immune system that are affected by pathogen threat. These processes motivative choices that help perceivers avoid unfamiliar stimuli that may include contamination dangers.
Examples of the influence perceived pathogen threat has on these processes include: avoidance of controllable risk, reduced desire for social affiliation, and devaluation of consumer products previously handled by strangers.
Additional lines of research on the behavioral immune system have shown that people engage in more reticent and conservative forms of behavior under conditions in which they feel more vulnerable to disease transmission. For instance, when the potential threat of disease is made salient, people tend to be less extraverted or sociable.
Close Relationships
The behavioral immune system influences potential mating choices and sexual behavior. High concern for chronic pathogen threats and environments with greater pathogen stress increase the value an individual places on physical attractiveness, and lessens preference for mates with physical abnormality or sex-divergent features. Among perceivers, cues of pathogen prevalence (real or perceived) are associated with more restricted sexual pursuits and attitudes to avoid infection. Opposite, more sexual opportunism is found in individuals with perceived insufficient immune systems for survival in environments with higher pathogen stress.
Stereotyping and Prejudice
Another outcome of behavioral immune system activity is prejudice and stereotyping of outgroup members. Individuals at higher risk of pathogen infection are more likely to stigmatize other individuals possessing cues of disease, real or perceived.
The disease–avoidant processes that characterize the behavioral immune system have been shown to:
contribute to prejudices against obese individuals, elderly
individuals, and people with physical disfigurements
or disabilities.
In addition, the behavioral immune system appears to contribute to xenophobia and ethnocentrism. This can be seen among pregnant women, which face higher infection-related vulnerability, that express an increase ethnocentric views. These attitudes might function as a way to avoid people with new pathogens or practices that local practices are unsuited to manage. One implication is that these prejudices tend to be exaggerated under conditions in which people feel especially vulnerable to the potential transmission of infectious diseases.
Group Processes and Cultural Norms
The behavioral immune system has the ability to impact group intragroup attitudes and behaviors. Research shows that:
pathogen stress is associated with higher social conformity and higher levels of disgust, which aids in pathogen avoidance and predictive of greater sensitivity to moral violations.
Some studies have used the behavioral immune system to explain the root of more fundamental dimensions of culture including the variance in: individualism/collectivism, social and political orientation, and religious beliefs, in response to levels of pathogen stress.
Collectivist cultures defined by behavioral manifestations such as ethnocentrism and social conformity which aid in pathogen avoidance, have been correlated with higher historical pathogen stress compared to individualistic cultures. Given that there might be benefits associated with individualistic cultures in the societies they create, individualist cultures also confer greater pathogen exposure. In environments with greater pathogen stress, the behavioral manifestations of collectivism that help avoid pathogens may serve an adaptive advantage.
Critiques of In-Group Preference
In-group preferences defined by the degree to which people prefer interacting with and investing in family, friends, and in group members has been suggested to be a function of the behavioral immune system in order to defend against pathogens. However, these studies on cross-population level data have been criticized for not incorporating non-independence variables and alternative hypotheses. In a follow up study, using measures the same measure for in-group preference, Hofstede's collectivism, Van de Vliert's in-group favoritism, and Fincher and Thornhill's strength of family ties, find that less government effectiveness is a better predictor of in-group preference than pathogen stress.
Implications for Immunology
Complimentary
Some research suggests that the behavioral immune system has implications for the functioning of the physiological immune system (PIS) too. One study found that the mere visual perception of diseased-looking people stimulated white blood cells to respond more aggressively to infection (as indicated by the production of the proinflammatory cytokine Interleukin 6 in response to a bacterial stimulus).
In other studies, exposure to visual environmental pathogen cues, in addition to increased feelings of disgust and prejudice responses associated with the behavioral immune system (BIS), upregulate oral and blood immune inflammatory biomarkers. This body of literature suggests that visual cues connected to the BIS may invoke PIS responses when pathogen threat is immediate.
Compensatory
In the absence of an immediate pathogen threat, the PIS and BIS may not be complimentary, but compensatory. For example, in an experiment that stimulated release of proinflammatory cytokines (IL-6, IL-1b, TNF-alpha) collected from healthy individuals, were not related to self-reported germ aversion, but in-vivo IL-6 levels were negatively correlated to germ aversion and perceived longevity. This research may highlight the function of the BIS for long-term health by decreasing proinflammatory responses (function of IL-6), linked to diseases of aging.
Research also indicates that immune-relevant interventions which target pathogen transmission can interrupt behavioral responses. For example, receiving a flu vaccination or washing one's hands can reduce the extent of negative interpersonal and intergroup attitudes elicited by disease cues and concerns.
Sickness Behavior
The large body of literature on the behavioral immune system is focused on behaviors triggered by pathogen cues in the environment and the role disgust plays in mitigating exposure before infection. However, the emotion associated with being sick, lassitude, that is triggered by an active infection may also act as behavioral defense mechanism against pathogens. One study suggests that lassitude may help fight against an active infection by:
-
reducing energetically expensive movement to
make more energy available to the immune system. - reducing exposure to additional infections and injuries that would increase the immune systems' workload.
-
promoting thermoregulatory behaviors that
facilitate immunity. -
regulating food consumption to be beneficial
for the host but detrimental to pathogens. -
deploying strategies that elicit caregiving
behavior from social allies.
COVID-19
The behavioral immune system's prediction of ingroup favoritism and ethnocentric beliefs has been applied to individual beliefs during the global pandemic, COVID-19. In several studies, individuals who scored higher in dispositional worry about disease reported stronger preference for restrictive travel bans on several regions of Asia. Experimental increase of pandemic salience also increased support of travel bans on high risk nation (China and Italy), but not on low risk nations like Canada and Mexico.
Another study measuring individual perceived vulnerability to disease (PVD) and responses to COVID-19 found that higher PVD was positively associated with stronger reactions to the threat of COVID-19, including increased anxiety, perceptions that people should alter their typical behavior, and self-reported importance of social distancing.
https://en.wikipedia.org/wiki/Behavioral_immune_system
We are prejudiced against all kinds of other people, based on superficial
physical features: We react negatively to facial disfigurement;
If I asked you why these prejudices exist and what one can do to
eliminate them, your answer probably wouldn't involve the words
"infectious disease." Perhaps it should.
What does infectious disease have to do with these prejudices? The
answer lies in something that I've come to call the "behavioral immune system." The behavioral immune system is our brain's way of engaging
in a kind of preventative medicine. It's a suite of psychological
mechanisms designed to detect the presence of disease-causing
parasites in our immediate environment, and to respond to those
things in ways that help us to avoid contact with them. This has
many important implications – for prejudice, for sexual attraction,
for social interaction, and even for the origins of cultural
differences. (And, yes, for health too.)
It makes immediate sense that people would develop aversions
against people who actually have infectious diseases. But why does
it also lead to these aversions to perfectly healthy people? Because
it's impossible to directly detect the presence of bacteria and
viruses and other microscopic parasites; and so we're forced to use
crude superficial cues. Consequently, we make mistakes. Some of
those mistakes lead to the irrational avoidance of things (including
people) that pose no infection risk at all.
Here's an example: Animal feces is loaded with parasites that can
make you ill. So if something looks like a pile of dog poop, you
probably won't eat it. That's smart. But what if I took some
delicious chocolate fudge and molded it into the shape of
poop? Research by Paul Rozin and his colleagues shows that a lot of people still won't eat it – even though
they know it's fudge! These people aren't responding to any rational
appraisal of infection risk; they are responding – automatically and
aversively – to appearances.
The same principle applies in our interactions with other people.
Our minds seem to be on the lookout for anything that looks like it
might be a symptom of infection. But there are lots of different
kinds of infections and lots of different kinds of symptoms;
consequently, anything anomalous about a person's appearance or
behavior (anything that deviates from our subjective sense of how a
"normal" person looks and acts) can automatically trigger aversive
emotional, cognitive, and behavioral responses. In recent years, my
collaborators and I have found that these disease-avoidant
psychological processes contribute to prejudices against people who
are disabled, obese, or old. These same processes also contribute to ethnocentrism and xenophobia.
One interesting implication is that these prejudices are
exaggerated when people feel vulnerable to infection, whereas the
prejudices are reduced among people who feel relatively safe. This
implication was neatly demonstrated in a study published in Evolution and Human Behavior, which examined prejudices in pregnant women. A woman's immune
system is suppressed during the first few weeks of pregnancy,
leaving her body more vulnerable to infection. One consequence is
that women are more sensitive to sights and smells and tastes that
trigger disgust. Another consequence is that, compared to women in
later stages of pregnancy, women in their first trimester show
higher levels of ethnocentrism and xenophobia.
The perceived threat of infection has interesting implications for
sexual attraction too. For instance, it's been known for a long time
that people find symmetrical faces more attractive. Why is this? One
possibility is that people with symmetrical faces are not only more
likely to be healthier themselves, but also more likely to produce
offspring with stronger immune systems. Consistent with this
reasoning, recent studies published in the Proceedings of the Royal Society and in the European Journal of Social Psychology reveal that the preference for symmetrical faces (especially
opposite-sex faces) is exaggerated under conditions in which people
are more keenly aware of the threat posed by infectious
diseases.
Another line of work focuses on social attitudes and interactions
more generally. In an article published last year, researchers at Arizona State University found that when the
threat of infection was especially salient, people were less
extraverted.
The implications of the behavioral immune system may also play out
at a societal level, and can help to explain worldwide
cross-cultural differences. If people behave differently depending
on their vulnerability to infection, then whole populations of
people may differ, depending on the local prevalence of parasites.
Damian Murray and I found that in countries characterized by high
levels of parasite prevalence, people are less extraverted and less open to new experiences, and also impose greater conformity pressures on one another. In collaboration with Corey Fincher and Randy Thornhill, we found
that parasite prevalence was a strong predictor of collectivistic value systems. Fincher and Thornhill have other evidence of similar effects. For
instance, in an article published in Biological Reviews, they report that parasite prevalence, and adaptive human
responses to it, may help explain cross-national differences in
political ideology and systems of governance.
Although the behavioral immune system is designed to reduce contact
with infectious parasites, infections still occur. Luckily, we have
the "real" immune system too, which works very hard to eliminate
those parasites from our bodies after infection occurs. These two
systems of anti-pathogen defense are physiologically distinct, but
they influence each other in interesting ways. A recent study published in Psychophysiology showed that when people experience disgust (the emotion that
signals threat of infection), there are increased markers of
immunological function in people's saliva. And in an experiment that my colleagues and I published last year
in Psychological Science, we found that the mere sight of other people's symptoms of
sickness (sneezes, sores, rashes) led perceivers' own white blood
cells to respond more aggressively to bacterial infection.
Medical scientists have been studying immunological defense for
decades. By contrast, it's only in the past few years that
psychological scientists have been doing research on the other immune system. Still, it's already apparent that this other
immune system – the behavioral immune system – has important
influences on a wide range of human affairs. In order to fully
explain why people think what they think or do what they do, we may
need to talk a lot more about the threat of infectious disease and
the psychological processes that, for better and worse, respond to
that threat.
Because immunological defence against pathogens is costly and merely
reactive, human anti-pathogen defence is also characterized by
proactive behavioural mechanisms that inhibit contact with pathogens
in the first place. This behavioural immune system comprises
psychological processes that infer infection risk from perceptual
cues, and that respond to these perceptual cues through the
activation of aversive emotions, cognitions and behavioural
impulses. These processes are engaged flexibly, producing
context–contingent variation in the nature and magnitude of aversive
responses. These processes have important implications for human
social cognition and social behaviour—including implications for
social gregariousness, person perception, intergroup prejudice, mate
preferences, sexual behaviour and conformity. Empirical evidence
bearing on these many implications is reviewed and discussed. This
review also identifies important directions for future research on
the human behavioural immune system—including the need for enquiry
into underlying mechanisms, additional behavioural consequences and
implications for human health and well-being.
1. INTRODUCTION
Humans and other animals have a long history of living in
proximity to parasitic organisms—bacteria, viruses, helminths—that cause
infectious diseases. This proximity imposed substantial selection pressures on
ancestral populations, resulting in many different adaptations that, in a
variety of ways, mitigate the potential fitness costs posed by these
pathogens. Most obviously, there evolved the sophisticated suite of
physiological mechanisms that define immunological defence systems, which are
designed to detect the presence of pathogens within the body and, when
detected, to mobilize physiological responses that encapsulate, kill or
otherwise eliminate these pathogenic intruders. Immunological defence against
infection has obvious fitness benefits, but can be substantially costly too
[1]. An immune response is metabolically costly (consuming caloric resources
that might otherwise be devoted to other important physiological systems) and
can be temporarily debilitating (because of fever, fatigue and other
physiological consequences of an aggressive immunological response). And, of
course, immunological defence is merely reactive—triggered only after the
pathogenic infection has occurred within the body.
Given these limits and costs associated with immunological defence against
pathogens, additional fitness benefits would have accrued from an additional
set of proactive mechanisms that—by guiding organisms' behaviour—inhibit
contact with pathogens in the first place. These mechanisms offer a sort of
behavioural prophylaxis against infection [2]. Indeed, it is not merely
metaphorical to suggest that these mechanisms comprise a behavioural immune
system that is separate from, and complementary to, the ‘real’ immune system
[3–5].
Behavioural defence against pathogens has been observed across a wide variety
of animal species [6,7]. Some forms of behavioural defence—such as
cytokine-induced sickness behaviour [8,9] and self-medication [10,11]—are
reactive, rather than proactive. But there is also abundant evidence of
proactive behavioural defence as well: wood ants collect pieces of coniferous
resin as a prophylactic defence against bacteria and pathogenic fungi [12];
bullfrog tadpoles selectively avoid swimming near infected tadpoles [13];
female mice respond aversively to the odours of male mice infected with
nematode parasites [14]; chimpanzees avoid social contact with (and may even
respond aggressively towards) other chimpanzees infected with polio [15]. In
short, just as the ‘real’ immune system is characterized by mechanisms that
facilitate adaptive immunological responses to pathogens that enter the body,
the behavioural immune system is characterized by mechanisms that facilitate
adaptive psychological responses to perceptual cues connoting the presence of
pathogens in the immediate perceptual environment—including the presence of
pathogens in conspecifics. The specific nature of the perceptual detection and
behavioural response mechanisms may vary across species, but the existence of
these detection and response mechanisms is common across species.
In recent years, the behavioural immune system has received considerable
attention in the study of human behaviour, with an emphasis on the specific
psychological mechanisms (pertaining to attention, perception, cognition and
emotion) that guide human behaviour. Much of this work has focused on one
specific emotion—disgust—that is associated with disease-avoidance behaviour,
on the specific kinds of perceptual things that elicit disgust, and on the
specific circumstances under which a disgust response is either exaggerated or
reduced [2,16,17]. This work has been reviewed extensively elsewhere [18,19].
My focus here is on a set of complementary programmes of research that focus
less on emotion and more on social cognition and social interaction—lines of
enquiry that explore how the behavioural immune system guides people's
perceptions of, thoughts about and behaviour towards other individuals within
their immediate social ecologies. The upshot is an emerging literature
documenting many subtle but important linkages between anti-pathogen defence
and the contours of human social life.
The behavioural immune system and the psychology of human
sociality
The Behavioral Immune System
In 2006, with this idea in mind, Schaller conceptualized a
complementary defense system – the behavioral immune system
(BIS) (Schaller, 2006). BIS is considered to be a motivational system that evolved
to modify behavior and reduce contact with infectious agents.
It is described as a coordinated suite of detection
mechanisms, which allow individuals to identify potential
sources of pathogens, and of emotional and cognitive
mechanisms, which respond to those cues and guide behaviors
that distance the individual from contagious sources (Schaller and Park, 2011).
Behavioral immune system likely has deep evolutionary roots.
It is evident in a wide range of species: from insects through
amphibians to mammals. Social lobsters and bullfrog tadpoles
detect and avoid conspecifics infected with a lethal pathogen
(Kiesecker et al., 1999; Behringer et al., 2006). In mice and rats several studies show that healthy
individuals keep distance and reduce interactions with
individuals whose immune system is activated (due to
injections of the bacterial extract LPS) (Arakawa et al., 2011; Boillat et al., 2015). Mandrill monkeys avoid grooming infected conspecifics and
refrain from the fecal matter (Poirotte et al., 2017). Thus, various groups of animals have developed behavioral
strategies to detect and limit contact with pathogens and
infectious individuals.
In humans, most support for the existence the BIS comes from
extensive studies of the emotional and physical reaction
commonly referred to as “disgust” (Curtis et al., 2004, 2011; Oaten et al., 2009; Tybur et al., 2013). We grimace, distance ourselves, and sometimes vomit in
response to sights and smells of carcasses, decomposing food,
bodily secretions, etc. Disgust often arises in response to
potentially contagious elements and usually drives us away
from them.
Additional support for the existence of the BIS in humans
comes from studies showing that we can detect sick individuals
through various cues…
https://www.frontiersin.org/articles/10.3389/fpsyg.2019.01004/full
The Behavioral Immune System (& Why It Matters)
Mark Schaller
Justin H. Park
How Coronavirus Bypasses Our Behavioral Immune System
Bypassing the Behavioral Immune System: If we’ve evolved an ability to detect and avoid pathogens,
why do we still get sick? There are a few answers to this
question. For one, the behavioral immune system relaxes
avoidance motivations to accommodate behaviors that require
some infection risk. Think about how parents scarcely bat an
eye when cleaning their baby’s vomit, or how lovers don’t
recoil at the thought of swapping spit. Even if such vomit
and saliva are no less likely to carry pathogens than
another baby’s vomit or another person’s saliva, a disgust
response would compromise investment in our helpless
offspring and in reproducing.
Further, while the behavioral immune system is far better
than nothing, it is imperfect. Features that trigger its
alarms sometimes do not correspond with pathogens, like the
stench of the durian fruit. And pathogens sometimes skirt by
undetected, like the E. coli that occasionally contaminates
leafy vegetables.
The behavioral immune system also does little to neutralize
the pathogens transmitted by the blood-sucking arthropods,
like mosquitoes, ticks, and tsetse flies. These creatures have
evolved to avoid detection for their own interests, and many
pathogens have evolved to capitalize on this stealthiness
(Zimmer, 2001).
we avoid sitting next to people who are obese, or old, or in a
wheelchair;
we favor familiar folks over folks that are foreign.
- Mark Schaller
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3189350/?report=classic
Mark Schaller - University of British Columbia
Justin H. Park - University of British Columbia & University
of Bristol
https://www2.psych.ubc.ca/~schaller/SchallerPark2011.pdf
https://psych.ubc.ca/profile/mark-schaller/
https://www.grad.ubc.ca/alumni/profile/justin-park
(And What We Can Do About It)
