Behavioral and Brain Sciences

Short Communication

Berkeley, Helmholtz, the moon illusion, and two visual systems

Helen E. Ross a1
a1 Department of Psychology, University of Stirling, Stirling FK9 4LA, Scotland


Berkeley and Helmholtz proposed different indirect mechanisms for size perception: Berkeley, that size was conditioned to various cues, independently of perceived distance; Helmholtz, that it was unconsciously calculated from angular size and perceived distance. The geometrical approach cannot explain size-distance paradoxes (e.g., moon illusion). The dorsal/ventral solution is dubious for close displays and untestable for far displays.