1. The Behavioral Immune System Evolutionary background.
- Selection pressures associated with infectious disease.
- Evolved mechanisms to manage infection risk.
Psychological consequences in contemporary environments.
- Lots of implications for lots of psychological phenomena.

2. Another set of adaptations: The “behavioral immune system”:
Functionally-specialized psychological mechanisms…
Detect presence of pathogens in environment.
Produce “useful” emotional and cognitive responses
that facilitated behaviors that were adaptive in the EEA.
(But not necessarily useful or adaptive now.)

3. Two general implications:
The behavioral immune system produces responses to many things that pose no actual risk of infection.
The behavioral immune system produces stronger responses when people perceive themselves to be more vulnerable to infection.

4. Specific implications for specific psychological phenomena…

5. Implications for emotion (disgust):

6. Implications for memory:
Enhanced recall for objects touched by sick people.
(Fernandes, Pandeirada, Soares, & Nairne, 2017)

7. Implications for visual attention:
Attention to disfigured faces.
(Ackerman et al., 2009)
- Compared to “normal” faces, disfigured faces hold attention longer.
- Especially when perceivers feel more vulnerable to infection.

8. Implications for social interaction:
Disease threat and extraversion.
(Mortensen et al., 2010)
When threat of infection is psychologically salient…
People report lower levels of extraversion.
People show more reluctant-to-interact movements.

9. Implications for consumer behavior:
Disease threat and willingness to buy used merchandise.
(Huang, Ackerman, & Sedlovskaya, 2017)
When threat of infection is psychologically salient…
People express reduced interest in used products.
In U.S. states that have higher rates of disease prevalence…
Used-product retail revenues are relatively lower.
(Even when controlling for other things that affect consumer behavior).

10. Implications for sexual behavior:
When threat of infection is psychologically salient,
people are more inclined to engage in safer sexual behavior.
Example: Fart spray and condoms study.
(Tybur et al., 2011)

11. Implications for interpersonal attraction:
- When threat of infection is psychologically salient,
people show a stronger preference for more symmetrical faces.
- This effect is especially strong when judging opposite-sex faces.
people show a stronger preference for physically attractive leaders.
(White, Kenrick, & Neuberg, 2013)

12. Implications for prejudice:
Obvious implications: Avoidance of sick people.
Additional implications:
Prejudices directed toward people who appear superficially “non-normal.”
Especially when perceivers feel vulnerable to infection.
Implications for prejudice reduction.

13. Subjective “foreign-ness” as a disease cue:
Increased xenophobia and ethnocentrism under conditions in which people feel more vulnerable to infection.
Example: Germ salience and immigration attitudes
(Faulkner et al., 2004)
Example: Pregnancy and ethnocentric attitudes.
(Navarrete, Fessler, & Eng, 2007)
Example: Rheumatoid arthritis and ethnocentric attitudes.
(Oaten, Stevenson, & Case, 2017)

14. Implications for conformity:
Costs and benefits of conformity / non-conformity.
Implication: When threat of infection is psychologically salient,
people are more conformist, and less tolerant of non-conformists.
Example:
(Murray & Schaller, 2012)
Percent of participants conforming to majority opinion:

15. Implications for moral judgment:
- Things that elicit more disgust
are judged to be more morally wrong.
- When people are more easily disgusted,
they judge norm violations more harshly.

16. Implications for political attitudes:
Liberalism: Willingness to embrace change
Conservatism: Prefer to maintain existing norms.
Implication: When people feel more vulnerable to infection, they express more conservative sociopolitical attitudes.
Example: Disgust and political conservatism.
(Lots of studies)

17. Australia / New Zealand
Results from one study (with data from 31,000 people):
Correlation between disgust sensitivity and identification as liberal vs. conservative.
Geographical region
Correlation
Canada
.21
United States
.17
Latin America
United Kingdom
Western Europe
Eastern Europe
.25
Australia / New Zealand
.19
East Asia
.24
South Asia
.32
Southeast Asia
.22
Middle East
.20
United States (N = 25,588)
Note: Effect of disgust mostly on conservative social attitudes (not economic attitudes).
(Inbar, Pizarro, Iyer, & Haidt, 2012)

18. Implications for political attitudes:
Liberalism: Willingness to embrace change
Conservatism: Prefer to maintain existing norms.
Implication: When people feel more vulnerable to infection, they express more conservative sociopolitical attitudes.
Example: Disgust and political conservatism.
(Lots of studies)
Example: Hand sanitizer dispenser experiment.
(Helzer & Pizarro, 2011)
Example: Ebola outbreak and voting intentions.
(Beall, Hofer, & Schaller, 2016)

19. Support for Canadian Conservative Party
2014
Support for Canadian Conservative Party
(Beall, Hofer, & Schaller, 2016)

20. (Beall, Hofer, & Schaller, 2016)
2014
(Higher values indicate relatively greater support for U.S. Republican Party candidates.)
(Beall, Hofer, & Schaller, 2016)