Perceptual Cognitive Universals as Reflections of the World

Roger N. Shepard

93-11-073

The Universality, invariance, and elegance of principles governing the universe may be reflected in principles of the minds that have evolved in that universe--provided that the mental principles are formulated with respect to the abstract spaces appropriate for the representation of biologically significant objects and their properties. (1) “Positions” and “motions” of objects conserve their “shapes” in the geometrically fullest and simplest way when represented as points and connecting geodesic paths in the six-dimensional manifold jointly determined by the Euclidean group of three-dimensional space and the symmetry group of each object. (2) “Colors” of objects attain constancy when represented as points in a three-dimensional vector space in which each variation in natural illumination is cancelled by application of its inverse from the three-dimensional linear group of terrestrial transformations of the invariant solar source. (3) “Kinds” of objects support optimal generalization and categorization when represented, in an evolutionarily shaped space of possible objects, as connected regions with associated weights determined by Bayesian revision of maximum-entropy priors.