Mechanisms of orientation sensitivity in the human visual system: Part I. Behavioral characteristics of orientation sensitivity. Influence of the task type, experimental conditions, and gender

Abstract

Orientation sensitivity in the human visual system was studied in three experiments. In the first experiment, 134 subjects determined orientation of the segments of short lines by selecting it from a set of reference orientations (the Benton test). In the second experiment, 41 subjects of those who passed the Benton test determined the proximity of oblique lines to cardinal axes and to the angle of 45 degrees. In the third experiment, the same subjects identified the orientation of 0, 90, 45, and 135 degrees. It was shown that the cardinal orientations (vertical and horizontal) were determined more accurately and faster than the oblique ones. In this case, the erroneous estimates of oblique lines were associated with the effect of “tilt normalization,” which was manifested in the bias towards basic axes. The type of errors was dependent on test conditions: at normal illumination and availability of additional visual information about the cardinal axes, the errors towards horizontal prevailed; and at low light conditions, the errors towards vertical were dominated. Significant gender differences were found: women were worse than men in performing the tasks that require accurate estimation of orientation (the first and third experiments), which indicates the deficiency of metric abilities in them. It is assumed that in women the most pronounced effect of intermediate orientations is associated with gender differences in brain organization of internal reference frame.