Perception of Oriented Lines

A wide range of empirical factors influences the perception of angles. In this scene, the subtenses of the four angular objects in the retinal stimulus are identical, each measuring approximately 90°. As a result of this variety of depicted cues about the attributes of the possible real-world sources (see text), the subtenses of the four identical angles look quite different. Click on the link above to convince yourself.

(Image by Beau Lotto - www.lottolab.org)