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 [email protected]


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.