Reconciling simplicity and likelihood principles in perceptual organization.

Two principles of perceptual organization have been proposed. The likelihood principle, following H. L. E yon Helmholtz ( 1910 / 1962), proposes that perceptual organization is chosen to correspond to the most likely distal layout. The simplicity principle, following Gestalt psychology, suggests that perceptual organization is chosen to be as simple as possible. The debate between these two views has been a central topic in the study of perceptual organization. Drawing on mathematical results in A. N. Kolmogorovs ( 1965)complexity heory, the author argues that simplicity and likelihood are not in competition, but are identical. Various implications for the theory of perceptual organization and psychology more generally are outlined. How does the perceptual system derive a complex and struc-tured description of the perceptual world from patterns of ac-tivity at the sensory receptors? Two apparently competing theo-ries of perceptual organization have been influential. The first, initiated by Helmholtz ( 1910/1962), advocates the likelihood principle: Sensory input will be organized into the most proba-ble distal object or event consistent with that input. The second, initiated by Wertheimer and developed by other Gestalt psy-chologists, advocates what Pomerantz and Kubovy (1986) called the simplicity principle: The perceptual system is viewed as finding the simplest, rather than the most likely, perceptual organization consistent with the sensory input . There has been considerable theoretical nd empirical con-troversy concerning whether likelihood or simplicity is the gov-erning principle of perceptual organization (e.g., Hatfield,