Behavioral 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.
It is theorized that the mechanisms that comprise the behavioral immune system evolved as a crude first line of defense against disease-causing pathogens.
[2][11] Early and current research on behavioral immune system activation has been focused on visual cues or triggers that elicit responses.
[12] In humans, body odors from diseased individuals are rated less desirable and likeable,[13] and perceived as unhealthier, more intense, and less pleasant.
Noninfectious physical and mental abnormalities including elderly appearance,[27][28] disabilities,[29] obesity,[30] and disfigurement[31][32] can act as cues of pathogen presence, when none are present.
[45] 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.
[51][28][21] Judgments, inferences, and decisions about people and objects are other cognitive processes recruited by the behavioral immune system that are affected by pathogen threat.
[52][53] Examples of the influence perceived pathogen threat has on these processes include: avoidance of controllable risk,[54] reduced desire for social affiliation,[55] and devaluation of consumer products previously handled by strangers.
[40][42] Opposite, more sexual opportunism is found in individuals with perceived insufficient immune systems for survival in environments with higher pathogen stress.
[26] 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.
[26] Some studies have used the behavioral immune system to explain the root of more fundamental dimensions of culture including the variance in: individualism/collectivism,[72] social and political orientation,[73][74][58] and religious beliefs,[75][76] in response to levels of pathogen stress.
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).
[82][83][84] This body of literature suggests that visual cues connected to the BIS may invoke PIS responses when pathogen threat is immediate.
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.
However, the emotion associated with being sick, lassitude, that is triggered by an active infection may also act as behavioral defense mechanism against pathogens.
In several studies, individuals who scored higher in dispositional worry about disease reported stronger preference for restrictive travel bans on several regions of Asia.
One study found that as COVID-19 cases increased, individuals reported higher concern about contracting the virus and showed greater levels of Right-Wing Authoritarianism, including conservatism and traditionalism.
