Proceedings of the Annual Meeting of the Cognitive Science Society

Learned generative models of human identity and appearance are typically high dimensional. However, social perceptionof faces is low dimensional. What is the dimensionality of face space in the mind of an observer? To estimate thisdimensionality, we begin with a simple observation: for any given person, there are many unrelated people who looksimilar to them. Next, we note that the very concept of strong resemblance exists only in low-dimensional spaces; inhigh-dimensional spaces, even nearest neighbors are far apart. Therefore, face space is of low dimensionality. How low?Using the scaling relationship between dimensionality and nth-nearest-neighbor distances, we empirically estimate thedimensionality of face space by measuring the ratio of JNDs between random pairs of faces and faces paired with theirnearest neighbors. We empirically estimate this ratio to be 0.76 [0.73, 0.79; 90% CI], which implies a dimensionality ofhuman face space between 7 and 12 dimensions.