Perceived similarity of shapes is an asymmetrical relationship: a study of typical contours

Two experiments are reported in which the relationship between perceived similarity amongst simple geometric solids and the set of projections arising from rotation of the typical contour of the solids about a vertical axis in its plane are examined. The results indicate (1) that judgments of similarity are affected by pronouncedness of typical contours, (2) similarity of simple geometrical solids is an asymmetrical attribute, in that where a set of possible projections of model X contains a set of possible projections of model Y, then model Y is judged as more similar to model X than X is to Y. The implications of this asymmetry for perceptual constancy and theories of object recognition are discussed.