The effects of retinal eccentricity and orientation on perceived length.

An experiment was performed to examine the effects of line orientation and retinal locus on the perceived length of a single line. Thirty-five male and female undergraduate volunteers each monocularly judged the length of five test lines presented in two orientations (horizontal and vertical) at five different retinal loci. Displacement of horizontal lines from the fovea on either the horizontal or vertical meridian produced decreases in perceived size. The perceived length of vertical lines, however, decreased only with displacements on the vertical meridian.