Visual 'normalization' near the vertical and horizontal.

Abstract

Eight expts. are reported, testing the possibility that the apparent righting of slightly tilted lines near the vertical and horizontal may be explained by the kinds of cortical field theory developed by Kohler and Wallach. The results indicate that apparent righting or normalization occurs to an extent of about 2[degree] with 10[degree] lines and that this effect is independent of the simultaneous or previous presence of contours that could have produced "satiation" in the Kohler-Wallach sense. This phenomenon also shows important functional differences from the disorientation phenomena reported by Wertheimer and by Asch and Witkin. Although anatomical and physiological inhomogeneities in the primary visual projection areas have been ruled out as explanations by the fact that the effective vertical and horizontal turn out to be detd. psychologically rather than by the retinal meridians, it is proposed that some kind of cortical theory must be devised to account for these effects. The special quale of "verticalness" which persists even when one''s head is tilted must itself have some representation in the nature of brain processes, and we must somehow extend our conception of satiation to include the neural representatives of visual aspects that are not contained directly in the geometry of the stimulus.