Reexamining Visual Orientation Anisotropies: A Bias Towards Simple Horizontal Stimuli on Temporal Order Judgments

Although not currently a widely accepted notion, evidence suggests an anisotropy between horizontal and vertical orientations in visual processing. While there is evidence of an early neurological bias due to a greater number of cortical neurons tuned to the horizontal orientation, recent behavioral evidence suggests a “horizontal effect”, where performance for broadband horizontal stimuli is worse compared to vertical and oblique. Importantly however, this effect has only been observed for complex stimuli and is speculated to counterbalance for the greater occurrence of horizontal stimuli in the environment. In this experiment, we used a staircase temporal order judgment task in three spatial configurations (horizontal, vertical, and both) to test for 1) a bias towards either horizontal or vertical simple stimuli, and 2) whether performance would vary across different planes of stimuli presentation. A bias towards horizontal stimuli was observed, but only when presented in the horizontal plane. Theoretical implications are discussed.