Don't Look, Don't Touch, Don't Eat: The Science Behind Revulsion

by Valerie Curtis

  3. R. Wrangham, Catching Fire: How Cooking Made Us Human (London: Profile Books, 2010).

  4. S. Mithen, The Prehistory of the Mind: A Search for the Origins of Art, Religion and Science (London: Thames and Hudson, 1996).

  5. M. Ridley, The Rational Optimist: How Prosperity Evolves (London: Fourth Estate, 2010); M. Tomasello and M. Carpenter, “Shared Intentionality,” Developmental Science 10, no. 1 (2007); K. N. Laland, N. Atton, and M. M. Webster, “From Fish to Fashion: Experimental and Theoretical Insights into the Evolution of Culture,” Philosophical Transactions of the Royal Society B 366, no. 1567 (2011); S. Bowles and H. Gintis, A Cooperative Species: Human Reciprocity and Its Evolution (Princeton, NJ: Princeton University Press, 2011).

  6. Freeland, “Pathogens and the Evolution of Primate Sociality.”

  7. There are many proposals for the functional basis of shame in the literature, none of which fit it to disgust and manners in quite this way. Closest is Dan Fessler, “Shame in Two Cultures: Implications for Evolutionary Approaches,” Journal of Cognition and Culture 4, no. 2 (2004). Roger Giner-Sorolla’s latest study also supports the idea of shame as a corollary to disgust; R. Giner-Sorolla and P. Espinosa, “Social Cuing of Guilt by Anger and of Shame by Disgust,” Psychological Science 22, no. 1 (2011).

  8. R. J. Stevenson et al., “Children’s Response to Adult Disgust Elicitors: Development and Acquisition,” Developmental Psychology 46, no. 1 (2010).

  9. V. Curtis et al., “Potties, Pits and Pipes: Explaining Hygiene Behaviour in Burkina Faso,” Social Science and Medicine 41, no. 3 (1995).

  10. V. Curtis, “Dirt, Disgust and Disease: A Natural History of Hygiene,” Journal of Epidemiology and Community Health 61, no. 8 (2007); V. S. Smith, Clean: A History of Personal Hygiene and Purity (Oxford: Oxford University Press, 2007).

  11. D. E. Brown, Human Universals (New York: McGraw-Hill, 1991).

  12. De Barra, “Attraction and Aversion.”

  13. N. Elias, The Civilizing Process, translated by E. Jephcott (1939; Malden, MA: Blackwell, 2000).

  14. Though not all ideas that get passed down are necessarily beneficial. R. Aunger, “Are Food Avoidances Maladaptive in the Ituri Forest of Zaire?” Journal of Anthropological Research 50 (1994).

  15. S. Mathew and R. Boyd, “Punishment Sustains Large-Scale Cooperation in Prestate Warfare,” Proceedings of the National Academy of Sciences USA 108, no. 28 (2011).

  16. J. Henrich, “The Evolution of Costly Displays, Cooperation and Religion: Credibility Enhancing Displays and Their Implications for Cultural Evolution,” Evolution and Human Behavior 30, no. 4 (2009).

  17. S. Nichols, “On the Genealogy of Norms: A Case for the Role of Emotion in Cultural Evolution,” Philosophy of Science 69 (2002).

  18. Elias, Civilizing Process; A. J. Packer and P. Espeland, How Rude! The Teenagers’ Guide to Good Manners, Proper Behavior, and Not Grossing People Out (Minneapolis, MN: Free Spirit Publishing, 1997).

  19. William of Wykeham (1324–1404), bishop of Winchester and chancellor of England, was the founder of Winchester College and New College, Oxford. “Maner mayks man” (c. 1350 Douce MS 52 no. 77), Oxford Dictionary of Proverbs website.

  Chapter Five

  1. A. Smith, Wealth of Nations (Wiley Online Library, 1999).

  2. E. J. Chaisson, “Energy Rate Density as a Complexity Metric and Evolutionary Driver,” Complexity 16, no. 3 (2011).

  3. W. Hamilton, “The Genetical Evolution of Social Behaviour,” Journal of Theoretical Biology 7 (1964).

  4. R. L. Trivers, “The Evolution of Reciprocal Altruism,” Quarterly Review of Biology 46 (1971).

  5. R. Joyce, The Evolution of Morality (Cambridge, MA: MIT Press, 2006).

  6. M. A. Nowak and K. Sigmund, “Evolution of Indirect Reciprocity,” Nature 437, no. 7063 (2005).

  7. W. H. Durham, Coevolution: Genes, Culture, and Human Diversity (Stanford, CA: Stanford University Press, 1991).

  8. Ibid.

  9. E. Sober and D. S. Wilson, Unto Others: The Evolution and Psychology of Unselfish Behavior (Cambridge, MA: Harvard University Press, 1999).

  10. M. Nowack and R. Highfield, Supercooperators: Evolution, Altruism and Human Behaviour; or, Why We Need Each Other to Succeed (New York: Free Press, 2011); Bowles and Gintis, A Cooperative Species. But also see Steven Pinker’s piece “False Allure of Group Selection.”

  11. We Need to Talk about Kevin, directed by Lynne Ramsay, 2011.

  12. T. Wheatley and J. Haidt, “Hypnotic Disgust Makes Moral Judgments More Severe,” Psychological Science 16, no. 10 (2005).

  13. S. Schnall et al., “Disgust as Embodied Moral Judgment,” Personality and Social Psychology Bulletin 34, no. 8 (2008).

  14. S. Schnall, J. Benton, and S. Harvey, “With a Clean Conscience,” Psychological Science 19, no. 12 (2008).

  15. C. B. Zhong and K. Liljenquist, “Washing Away Your Sins: Threatened Morality and Physical Cleansing,” Science 313, no. 5792 (2006).

  16. J. V. Fayard et al., “Is Cleanliness Next to Godliness? Dispelling Old Wives’ Tales: Failure to Replicate Zhong and Liljenquist (2006),” Journal of Articles in Support of the Null Hypothesis 6, no. 2 (2009). People conditioned to feel disgust at certain words also didn’t show any more moral disgust when these words were incorporated into scenarios of moral wrongdoing: B. David and B. O. Olatunji, “The Effect of Disgust Conditioning and Disgust Sensitivity on Appraisals of Moral Transgressions,” Personality and Individual Differences 50, no. 7 (2011). Other disgust researchers have told me that they couldn’t replicate the Wheatley and Haidt and Schnall findings. More studies are still coming in: e.g., Z. Yan, D. Ding, and L. Yan, “To Wash Your Body, or Purify Your Soul: Physical Cleansing Would Strengthen the Sense of High Moral Character,” Psychology 2, no. 9 (2011); K. J. Eskine, N. A. Kacinik, and J. J. Prinz, “A Bad Taste in the Mouth,” Psychological Science 22, no. 3 (2011); K. Liljenquist, C. B. Zhong, and A. D. Galinsky, “The Smell of Virtue: Clean Scents Promote Reciprocity and Charity,” Psychological Science 21, no. 3 (2010).

  17. H. A. Chapman et al., “In Bad Taste: Evidence for the Oral Origins of Moral Disgust,” Science 323, no. 5918 (2009).

  18. E. Royzman and R. Kurzban, “Minding the Metaphor: The Elusive Character of Moral Disgust,” Emotion Review 3, no. 3 (2011).

  19. Stevenson et al., “Children’s Response to Adult Disgust Elicitors.”

  20. Giner-Sorolla and Espinosa, “Social Cuing of Guilt.”

  21. Martin Kavaliers, personal communication.

  22. J. Moll et al., “The Moral Affiliations of Disgust: A Functional MRI Study,” Cognitive and Behavioral Neurology 18, no. 1 (2005): 68–78.

  23. A. G. Sanfey et al., “The Neural Basis of Economic Decision-Making in the Ultimatum Game,” Science 300, no. 5626 (2003).

  24. We haven’t specifically examined the question of incest disgust. Debra Lieberman and her colleagues would argue that this is another special category of moral disgust, one that may originate from the adaptive need to avoid inbreeding: D. Lieberman, J. Tooby, and L. Cosmides, “The Architecture of Human Kin Detection,” Nature 445, no. 7129 (2007).

  25. Our view of the evolved basis of the control of behavior and the role of emotions is set out more fully in Aunger and Curtis, “Kinds of Behaviour.” It is also the subject of a forthcoming book with Oxford University Press.

  26. A. R. Damasio, Descartes’ Error: Emotion, Reason, and the Human Brain (New York: Putnam, 1994).

  Chapter Six

  1. Of course, what is meant by “better” is a topic for philosophers. Some say we can’t describe those higher values, but I’m in the camp that thinks that we can and should do so, as is Sam Harris: The Moral Landscape: How Science Can Determine Human Values (New York: Free Press, 2011).

  2. UNICEF and World Health Organization, “Diarrhoea: Why Children Are Still Dying and What Can Be Done” (New York: UNICEF, 2009); Liu et al., “Causes of Child Mortality.”

  3. World Health Organization and UNICEF, Progress on Sani
tation and Drinking-Water: 2010 Update (Geneva: World Health Organization, 2010).

  4. Our original figure was a million children, which we have revised downward because of the global fall in infant mortality. K. Greenland et al., “Editorial: Can We Afford to Overlook Hand Hygiene Again?” Tropical Medicine and International Health 18, no. 3 (2013); V. Curtis and S. Cairncross, “Effect of Washing Hands with Soap on Diarrhoea Risk in the Community: A Systematic Review,” Lancet Infectious Diseases 3 (2003).

  5. V. Curtis et al., “Hygiene: New Hopes, New Horizons,” Lancet Infectious Diseases 11, no. 4 (2011).

  6. T. Rabie and V. Curtis, “Handwashing and Risk of Respiratory Infections: A Quantitative Systematic Review,” Tropical Medicine and International Health 11, no. 3 (2006); I. C.-H. Fung and S. Cairncross, “Effectiveness of Handwashing in Preventing SARS: A Review,” Tropical Medicine and International Health 11, no. 11 (2006); T. Jefferson et al., “Physical Interventions to Interrupt or Reduce the Spread of Respiratory Viruses: Systematic Review,” British Medical Journal 336 (2008); P. M. Emerson et al., “A Review of the Evidence for the ‘F’ and ‘E’ Components of the SAFE Strategy for Trachoma Control,” Tropical Medicine and International Health 5, no. 8 (2000); D. B. Huang and J. Zhou, “Effect of Intensive Handwashing in the Prevention of Diarrhoeal Illness among Patients with AIDS: A Randomized Controlled Study,” Journal of Medical Microbiology 56, no. 5 (2007); J. H Humphrey, “Child Undernutrition, Tropical Enteropathy, Toilets, and Handwashing,” Lancet 374 (2009).

  7. V. A. Curtis et al., “Hygiene in the Home: Relating Bugs to Behaviour,” Social Science and Medicine 57, no. 4 (2003).

  8. V. Curtis, L. Danquah, and R. Aunger, “Planned, Motivated and Habitual Hygiene Behaviour: An Eleven Country Review,” Health Education Research 24, no. 4 (2009).

  9. Curtis, Danquah, and Aunger, “Planned, Motivated and Habitual Hygiene Behaviour.”

  10. B. E. Scott et al., “Marketing Hygiene Behaviours: The Impact of Different Communications Channels on Reported Handwashing Behaviour of Women in Ghana,” Health Education Research 22, no. 4 (2007).

  11. The ad can be seen at http://www.youtube.com/watch?v=w2qRcMTstzc.

  12. G. Judah et al., “Experimental Pretesting of Hand-Washing Interventions in a Natural Setting,” American Journal of Public Health 99, no. S2 (2009).

  13. NHS website, http://www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/@dh/@en/documents/digitalasset/dh_098680.pdf.

  14. G. J. Rubin, H. W. W. Potts, and S. Michie, “The Impact of Communications about Swine Flu (Influenza H1N1v) on Public Responses to the Outbreak: Results from 36 National Telephone Surveys in the UK,” Health Technology Assessment 14, no. 34 (2010).

  15. D. S. Fleischman et al., “Sensor Recorded Changes in Rates of Hand Washing with Soap in Response to the Media Reports of the H1N1 Pandemic in Britain,” BMJ Open 1 (2011).

  16. A. Brian et al., “Superamma: A Cluster Randomized Trial of a Village-Level Intervention to Promote Handwashing with Soap in Rural Andhra Pradesh, India” (unpublished manuscript, 2013).

  17. BBC website, http://www.bbc.co.uk/news/world-asia-india-20202339.

  18. Golden Poo Awards, http://www.thegoldenpooawards.org/.

  19. British Heart Foundation, “Give Up before You Clog Up,” edited by UK Department of Health, advertisement on YouTube, http://www.youtube.com/watch?v=cDAN7Oi62e0, 2003.

  20. D. Hammond et al., “Graphic Canadian Cigarette Warning Labels and Adverse Outcomes: Evidence from Canadian Smokers,” American Journal of Public Health 94, no. 8 (2004).

  21. G. Gilbert, director, Jamie’s School Dinners (Channel 4 [UK], 2005).

  22. New York City Department of Health and Mental Hygiene, http://www.youtube.com/watch?v=0mt-i2aypew.

  23. Both fear and disgust operate on the smoke-alarm principle, better to be safe than sorry. In the case of fear, it is adaptive to overdetect snakes in the grass on average, and so waste energy avoiding a harmless stick, as the rare snakebite is extremely costly. In the same way it is better, on average, to avoid food that smells a bit off, even if it means missing a meal, than it is to eat everything and perhaps die from typhoid. See Nesse, “Natural Selection and the Regulation of Defenses”; M. G. Haselton and D. Nettle, “The Paranoid Optimist: An Integrative Evolutionary Model of Cognitive Biases,” Personality and Social Psychology Review 10, no. 1 (2006).

  24. C.W. Schmidt, “The Yuck Factor: Where Disgust Meets Discovery,” Environmental Health Perspective 116, no. 12 (2008).

  25. S. Earle, “Factors Affecting the Initiation of Breastfeeding: Implications for Breastfeeding Promotion,” Health Promotion International 17, no. 3 (2002).

  26. A. Corbin, The Foul and the Fragrant: Odor and the French Social Imagination (Cambridge, MA: Harvard University Press, 1988).

  27. Herz, That’s Disgusting.

  28. W. Marsiglio, “Attitudes toward Homosexual Activity and Gays as Friends: A National Survey of Heterosexual 15- to 19-Year-Old Males,” Journal of Sex Research 30, no. 1 (1993).

  29. R. Kurzban and M. R. Leary, “Evolutionary Origins of Stigmatization: The Functions of Social Exclusion,” Psychological Bulletin 127, no. 2 (2001).

  30. J. H. Park, J. Faulkner, and M. Schaller, “Evolved Disease-Avoidance Processes and Contemporary Anti-Social Behavior: Prejudicial Attitudes and Avoidance of People with Physical Disabilities,” Journal of Nonverbal Behavior and Brain Sciences 27, no. 2 (2003); J. H. Park, M. Schaller, and C. S. Crandall, “Pathogen-Avoidance Mechanisms and the Stigmatization of Obese People,” Evolution and Human Behavior 28, no. 6 (2007).

  31. Park, Faulkner, and Schaller, “Evolved Disease-Avoidance Processes”; Park, Schaller, and Crandall, “Pathogen-Avoidance Mechanisms”; L. A. Duncan and M. Schaller, “Prejudicial Attitudes toward Older Adults May Be Exaggerated When People Feel Vulnerable to Infectious Disease: Evidence and Implications,” Analyses of Social Issues and Public Policy 9, no. 1 (2009).

  32. Curtis, Aunger, and Rabie, “Evidence That Disgust Evolved.”

  33. P. Magin et al., “Psychological Sequelae of Acne Vulgaris: Results of a Qualitative Study,” Canadian Family Physician 52, no. 8 (2006); A. P. Alio et al., “The Psychosocial Impact of Vesico-Vaginal Fistula in Niger,” Archives of Gynecology and Obstetrics 284 (2011).

  34. R. Dahle, “Lukt, fukt og skam” (Bodily smells, wetness and shame; paper presented at Norsk Selskap for Aldersforskning, Oslo, September 9, 1999).

  35. L. W. Isaksen, “Toward a Sociology of (Gendered) Disgust Images of Bodily Decay and the Social Organization of Care Work,” Journal of Family Issues 23, no. 7 (2002).

  36. J. Wrubel and S. Folkman, “What Informal Caregivers Actually Do: The Caregiving Skills of Partners of Men with AIDS,” AIDS Care 9 (1997). See also the portrayal of the effects of shame in disease and age for a loving couple in Micheal Haneke’s penetrating film Amour.

  37. A. R. Hochschild, The Managed Heart: The Commercialization of Human Feelings (Berkeley: University of California Press, 1983).

  38. M. Sommer, “Where the Education System and Women’s Bodies Collide: The Social and Health Impact of Girls’ Experiences of Menstruation and Schooling in Tanzania,” Journal of Adolescence 33, no. 4 (2010).

  39. T. Crofts and J. Fisher, “Menstrual Hygiene in Ugandan Schools: An Investigation of Low-Cost Sanitary Pads,” https://dspace.lboro.ac.uk/dspace-jspui/handle/2134/9399, 2012.

  40. B. O. Olatunji et al., “Multimodal Assessment of Disgust in Contamination-Related Obsessive-Compulsive Disorder,” Behaviour Research and Therapy 45 (2007).

  41. Rachman, “Fear of Contamination”; S. A. Rasmussen and J. L. Eisen, “Clinical and Epidemiologic Findings of Significance to Neuropharmacologic Trials in OCD,” Psychopharmacology Bulletin 24, no. 3 (1988).

  42. Tolin, Worhunsky, and Maltby, “Sympathetic Magic.”

  43. G. J. Rubin et al., “Public Perceptions, Anxiety and Behavioural Change in Relation to the Swine Flu Outbreak: A Cross-Sectional Telephone Survey,” British Medical Journal 33
9 (2009); L. A. Page et al., “Using Electronic Patient Records to Assess the Impact of Swine Flu (Influenza H1N1) on Mental Health Patients,” Journal of Mental Health 20, no. 1 (2011).

  44. W. J. Magee et al., “Agoraphobia, Simple Phobia, and Social Phobia in the National Comorbidity Survey,” Archives of General Psychiatry 53, no. 2 (1996).

  45. P. Muris et al., “Disgust and Psychopathological Symptoms in a Nonclinical Sample,” Personality and Individual Differences 29 (2000).

  46. B. O. Olatunji and C. N. Sawchuk, “Disgust: Charcteristic Features, Social Manifestations and Clinical Implications,” Journal of Social and Clinical Psychology 24, no. 7 (2005).

  47. Davey et al., “Cross-Cultural Study of Animal Fears.”

  48. S. R. Woody, C. McLean, and T. Klassen, “Disgust as a Motivator of Avoidance of Spiders,” Journal of Anxiety Disorders 19, no. 4 (2005).

  49. Fleischman and Fessler, “Progesterone’s Effects.”

  50. M. L. Phillips et al., “Disgust: The Forgotten Emotion of Psychiatry,” British Journal of Psychiatry 172 (1998); G. C. L. Davey et al., “Disgust and Eating Disorders,” European Eating Disorders Review 6, no. 3 (1998); N. A. Troop, J. L. Treasure, and L. Serpell, “A Further Exploration of Disgust in Eating Disorders,” European Eating Disorders Review 10, no. 3 (2002); Muris et al., “Disgust and Psychopathological Symptoms”; B. Mayer et al., “Does Disgust Enhance Eating Disorder Symptoms?” Eating Behaviors 9, no. 1 (2008).