This program of research is concerned with how primates (including children and adults) see the world, and how and when they fall prey to perceptual and cognitive illusions.  We are interested in many illusions, including the Solitaire illusion (top left image, where many people would respond when asked that there are more white dots in the array at the left, even though both arrays have 16 dots of each color), the Delboeuf illusion (bottom left image), where central dots (or servings of food as at bottom right) appear larger when surrounded by a close ring or small plate compared to a larger ring or larger plate, and the less-is-more effect where containers that are more overflowed appear to hold more (top right image, where the number of marshmallows in each container is actually the same, but many people think the one at the left has more - something chimpanzees also think!). For a recent news release on some of this research, click here.  We also are interested in how context affects perception and choice behavior.  Specifically, we are studying the role of anchoring effects, decoy effects, and similar effects that may generate heuristics in primates and generate choice biases.

Selected Related Publications:

Beran, M. J., Perdue, B. M., Kelly, A. K., & Parrish, A. E. (2017). What’s in a face (made of foods)? Comparing children’s and monkeys’ perception of faces in face-like images of food. Animal Behavior and Cognition, 4, 324-339. Click here for full paper.

Parrish, A. E., James, B. J., & Beran, M. J. (2017). Exploring whether nonhuman primates show a bias to overestimate dense quantities. Journal of Comparative Psychology, 131, 59-68. NCBI Logo

Agrillo, C., Parrish, A. E., & Beran, M. J. (2016). How illusory is the Solitaire illusion? Assessing the degree of misperception of numerosity in adult humans. Frontiers in Psychology, 7,1663. doi: 10.3389/fpsyg.2016.01663. Click here for a PDF file of this paper.

Parrish. A. E., Agrillo, C., Perdue, B. M., & Beran, M. J. (2016). The elusive illusion: Do children (Homo sapiens) and capuchin monkeys (Cebus apella) see the Solitaire illusion? Journal of Experimental Child Psychology, 142, 83-95. NCBI Logo

Agrillo, C., Gori, S., & Beran, M. J. (2015). Do rhesus monkeys (Macaca mulatta) perceive illusory motion? Animal Cognition, 18, 895-910. NCBI Logo

Agrillo, C., Parrish, A. E., & Beran, M. J. (2014). Do rhesus monkeys (Macaca mulatta) perceive the Zöllner illusion?  Psychonomic Bulletin & Review, 21, 986-994. NCBI Logo

Parrish, A. E., & Beran, M. J. (2014). When less is more: Like humans, chimpanzees (Pan troglodytes) misperceive food amounts based on plate size. Animal Cognition, 17, 427-434. NCBI Logo

Parrish, A. E., & Beran, M. J. (2014). Chimpanzees sometimes see fuller as better: Judgments of food quantities based on container size and fullness. Behavioural Processes, 103, 184-191. NCBI Logo