I study social cognition across the lifespan, focusing on coalitional psychology—the processes that (1) track relationships between people and (2) generate expectations and motivate behaviors with respect to these relationships.





NEW: Pietraszewski, D., Cosmides, L., & Tooby, J. (2014). The content of our cooperation, not the color of our skin: An alliance detection system regulates categorization by coalition and race, but not sex. PLoS ONE  9(2): e88534. doi:10.1371/journal.pone.0088534  PDF  Press Release


Pietraszewski, D., & Schwartz, A. (2014). Evidence that accent is a dedicated dimension of social categorization, not a byproduct of perceptual salience, familiarity, or ease-of-processing. Evolution and Human Behavior, 35, 43-50.  PDF  Supplementary Materials


Pietraszewski, D., & Schwartz, A. (2014). Evidence that accent is a dimension of social categorization, not a byproduct of coalitional categorization. Evolution and Human Behavior, 35, 51-57.  PDF


Pietraszewski, D., & German, T. C. (2013). Coalitional psychology on the playground: Reasoning about indirect social consequences in preschoolers and adults. Cognition, 126, 352-363.  PDF


Pietraszewski, D. (2013). What is group psychology? Adaptations for mapping shared intentional stances. In Banaji, M., & Gelman, S., (Eds).  Navigating the social world: What infants, children, and other species can teach us (pp. 253-257). New York: Oxford University Press.  PDF


Pietraszewski, D. (2012). The elementary dynamics of intergroup conflict and revenge. Behavioral and Brain Sciences, 36, 32-33. PDF


Pietraszewski, D., & Wertz. A. E. (2011). Reverse engineering the structure of cognitive mechanisms.  Behavioral and Brain Sciences, 34, 209-210.  PDF


Pietraszewski, D. (2011). What is argument for? An adaptationist approach to argument and debate.  Behavioral and Brain Sciences, 34, 86-87.  PDF




My research examines the psychological processes that allow people to track social relationships and alliances—the alliance detection system, and how this relates to the representation of race, gender, age, accent, and political affiliation. This work has lead to the discovery of experimental circumstances that selectively reduce racial categorization.


A separate project examines how relationship information is used to predict indirect social consequences—the behavior and reactions of uninvolved bystanders—in children and adults. 


I also study coalitional psychology in infants, exploring how group size impacts infants’ decisions and evaluations.


Other projects include the psychology of resource conflict (adapted from the asymmetric war of attrition model from evolutionary biology), and models of intergroup conflict.