Psychophysical Investigations of Incomplete Forms and Forms

Incompleteness and background are two important types of variance found in images of objects. It has been proposed that a bidirectional network within the visual cortex allows organisms to cope with this variability. In this thesis, the problems of incompleteness and background are defined in detail and various bidirectional (feedforward and backprojecting) network solutions are proposed and discussed. Three experiments were performed to investigate how such a network might recognize objects which are incomplete or backgrounded. In the first experiment, spatial and temporal manipulations of illusory contours are used to test the hypothesis that a bidirectional network is responsible for illusory contour formation. In the second experiment, incomplete and backgrounded versions of the same object are studied to test the hypothesis that the real purpose of neural back projections is segmentation rather than object completion. And, in the third experiment, novel camouflage objects are used to study the ability or inability of the brain to learn new object representations, when the brain is without the benefit of active back projections.