The Gelb Effect: Brightness Contrast Plus Attention

Abstract

Early in twentieth century, a new approach to understanding of visual perception began to develop. This approach stressed importance of relations among parts of visual field and insisted that percept could not be explained in terms of elements impinging on retina. This is point inherent in writings of von Ehrenfels (1890) on 'Gestaltqualitat,' in early work of Wertheimer on phi phenomenon (1912), in formulation by Koffka (1935) of principles of organization of visual world, and in many demonstrations produced by 'Gestalt psychology.' The essence of point has been summed up in often quoted, and sometimes misquoted, statement that the whole is different from sum of its parts.