The Psychology of Purity

Psych 4790/6790
Professor David Pizarro
Department of Psychology
Cornell University

Course Description

Many moral and religious systems tell us to keep a “pure heart,” and that immoral acts “pollute” our souls. We dislike dirty plays and dirty players in sports, and we keep our children away from dirty movies. We are also motivated to maintain purity in the less metaphorical sense—most cultures have norms about keeping bodies and living spaces clean. We even have an emotion—disgust—that seems especially attuned to certain kinds of dirtiness (such as bodily fluids and rotten food).

The concept of purity, then, appears to be a deep aspect of human psychology—from the basic motivation to maintain physical purity, to the metaphors of purity and cleanliness that feature heavily in morality and religion across cultures. In this course we will look at the psychology of purity by reading widely on the topic, including historical, religious, anthropological, and psychological sources that center on purity in both the physical and moral/spiritual sense. Our aim will be to understand how this basic notion of pure/impure or clean/dirty has come to shape our psychology and our culture.

Weekly Schedule and Readings

Week 1 — Jan 21: Introduction

Introduction to the topic and syllabus, expectations for the course, and personal introductions.

Week 2 — Jan 28: What Is Purity? Conceptual Foundations

Feder, Yitzhaq. (2024) “Getting Down and Dirty with Impurity, ” Biblical Archaeology Review 50.4 (2024): 72–74. [very short]

Douglas, M. (1966). Purity and Danger: An Analysis of Concepts of Pollution and Taboo. London: Routledge. (Ch. 1, “Ritual Uncleanliness” and Ch.2, “Secular Defilement.”)

Urban, H. B. (2017). Purity. In M. Stausberg & S. Engler (Eds.), The Oxford Handbook of the Study of Religion (pp. 609–621). Oxford University Press.

Forth, G. (2017). Purity, Pollution, and Systems of Classification . In The International Encyclopedia of Anthropology, H. Callan (Ed.).

Week 3 — Feb 4: The Evolution of Cleanliness and Hygiene

Cantini, D., Choleris, E., & Kavaliers, M. (2024). Neurobiology of pathogen avoidance and mate choice: Current and future directions. Animals, 14(2), 296.

Curtis, V. A. (2007). Dirt, disgust and disease: a natural history of hygiene. Journal of Epidemiology & Community Health, 61(8), 660-664.

Sarabian, C., Curtis, V., & McMullan, R. (2018). Evolution of pathogen and parasite avoidance behaviours. Philosophical Transactions of the Royal Society B: Biological Sciences, 373(1751), 20170256.

Week 4 — Feb 11: Disease and the Evolution of Culture

Thornhill, R., & Fincher, C. L. (2014). Stress theory of values and sociality ( Ch. 3, The parasite-stress theory of values). Berlin: Springer.

Schaller, M., & Murray, D. R. (2010). Infectious diseases and the evolution of cross-cultural differences. In M. Schaller, A. Norenzayan, S. J. Heine, T. Yamagishi, & T. Kameda (Eds.), Evolution, culture, and the human mind (pp. 243–256). New York, NY: Psychology Press.

Fincher, C. L., & Thornhill, R. (2012). Parasite-stress promotes in-group assortative sociality: The cases of strong family ties and heightened religiosity . Behavioral and Brain Sciences, 35(2), 61-79.

Week 5 — Feb 18: Some Basics on the Emotion of Disgust

Rozin, P., Haidt, J., & McCauley, C. R. (1999). Disgust: The body and soul emotion. In T. Dalgleish & M. Power (Eds.), Handbook of cognition and emotion (pp. 429–445). Wiley.

Inbar, Y., & Pizarro, D. A. (2022). How disgust affects social judgments. In Advances in Experimental Social Psychology, 109-166, 65. Academic Press.

Tybur, J. M., Çınar, Ç., Karinen, A. K., & Perone, P. (2018). Why do people vary in disgust? Philosophical Transactions of the Royal Society B: Biological Sciences, 373, 1751, 20170204.

Week 6 — Feb 25: (No Class)

Week 7 — Mar 4: Purity and Contagion

Rozin, P., Millman, L., & Nemeroff, C. (1986). Operation of the laws of sympathetic magic in disgust and other domains. Journal of Personality and Social Psychology, 50(4), 703–712.

Nemeroff, C., & Rozin, P. (2008). Back in touch with contagion: The role of interaction in perception of illness and contamination. In R. A. Murphy (Ed.), Oxford handbook of thinking and reasoning (pp. 106–123). Oxford, UK: Oxford University Press.

Huang, J. Y., Ackerman, J. M., & Newman, G. E. (2017). Catching (up with) magical contagion: A review of contagion effects in consumer contexts. Journal of the Association for Consumer Research, 2(4), 430–443.

Week 8 — Mar 11: Disorder, Disgust, and Psychopathology

Knowles, K. A., Jessup, S. C., & Olatunji, B. O. (2018). Disgust in anxiety and obsessive-compulsive disorders: Recent findings and future directions. Download Disgust in anxiety and obsessive-compulsive disorders: Recent findings and future directions. Current Psychiatry Reports, 20(9), 68.

Kang, L. L., Rowatt, W. C., & Fergus, T. A. (2016). Moral foundations and obsessive-compulsive symptoms: A preliminary examination. Journal of Obsessive-Compulsive and Related Disorders, 11, 22-30.

Greenberg, D., & Huppert, J. D. (2010). Scrupulosity: A unique subtype of obsessive-compulsive disorder. Current Psychiatry Reports, 12(4), 282-289.

Week 9 — Mar 18: Purity as a Moral Foundation

Shweder, R. A., Much, N. C., Mahapatra, M., & Park, L. (1997). The “big three” of morality (autonomy, community, and divinity) and the “big three” explanations of suffering. In A. Brandt & P. Rozin (Eds.), Morality and health (pp. 119–169). Routledge.

Haidt, J., & Joseph, C. (2004). Intuitive ethics: How innately prepared intuitions generate culturally variable virtues. Daedalus, 133(4), 55-66.

Graham, J., Haidt, J., Koleva, S., Motyl, M., Iyer, R., Wojcik, S. P., & Ditto, P. H. (2013). Moral foundations theory: The pragmatic validity of moral pluralism. In Advances in Experimental Social Psychology (Vol. 47, pp. 55-130). Academic Press.

Week 10 — Apr 1 (No Class, Spring Break)

Week 11 — Apr 8: Problems with Study of Purity in Psychology (Conceptual and Methodological)

Kollareth, D., Brownell, H., Durán, J. I., & Russell, J. A. (2023). Is purity a distinct and homogeneous domain in moral psychology? Journal of Experimental Psychology: General, 152(1), 211.

Gray, K., DiMaggio, N., Schein, C., & Kachanoff, F. (2023). The problem of purity in moral psychology. Personality and Social Psychology Review, 27(3), 272-308.

Week 12 — Apr 15: Should Purity Matter?

Selected readings [tbd] from Nussbaum, M. C. (2009). Hiding from humanity: Disgust, shame, and the law. Princeton University Press.

Selected readings [tbd] form Manne, K. (2017). Down girl: The logic of misogyny. Oxford University Press.

Shotwell, A. Against purity. Differens Magazine, Winter 2022-23.

Gish, E. (2025). When purity cannot save us: On matter out of place and democratic hope. Download When purity cannot save us: On matter out of place and democratic hope. In Evangelical Purity Culture and Its Discontents (pp. 136-152). Routledge.