FIELD OF RETINAL INDUCTION AND OPTICAL ILLUSION

Abstract

The field of retinal induction was mapped out by employing the method used previously for studies of simultaneous contrast. The effect of induction manifests itself in changes in electrical excitability of the eye after its exposure to inducing light and white test-light in succession. The field mapped out by this method is circular around a circle, triangular around a triangle, but cruciform around a square. The induction at a point in the middle of a cross bounded by 4 squares is lower than at any parts of the cross, while the phenomenon is not so conspicuous on an oblique cross bounded by 4 rhombs. Wertheimer-Benary''s contrast, which is 1 of the most important phenomena for Gestalt psychology, can be demonstrated more quantitatively and more directly by this physiological method. It seems likely that optical illusion takes place when the field around a figure is deformed by some modification of the figure or by other additional figures. This relation was demonstrated by measuring the field of retinal induction set up by the well-known figures of Muller-Lyer, Zollner, Hering, Kohler, etc. The field set up by a vertical bar extends over a longer distance than does the one set up by a horizontal bar of one and the same length, and this fact suggests that the so-called anisotropy of visual space is due to such functional anisotropy of the retina. The importance of retinal induction was emphasized especially for the problem of visual acuity, and the vernier effect was accounted for on the basis of field patterns. It was shown by many examples that laws governing the field of retinal induction are qualitatively different from those governing the electric, magnetic, and gravitational fields.