Some Effects of Perceived Size, Retinal Size, and Retinal Speed on Duration of Spiral Aftereffect

Abstract

Measures of perceived size, perceived distance, and perceived stimulus speed of rotating spirals were obtained in addition to the duration of the spiral aftereffect. Two major conditions were used: Size Constant—a 4-in. spiral was positioned to subtend visual angles of 1/2°, 1°, 2°, 4°, or 8° with 7 rates of retinal speed (10-100 minarcs/sec.) used at each angle; Angle Constant —3 sizes of spirals were positioned so that each subtended visual angles of 2°, 4°, and 8° with physical speed held constant (75 rpm) in one case and retinal speed (45 minarcs/sec.) held constant in another. SAE durations were significantly affected by low retinal speeds, by small visual angles and by perceived size per unit of retinal size.