Fig. 1.
Müller-Lyer stimuli. (A) The standard Müller-Lyer stimulus. (B) Variation in which the arrowheads and tails are replaced by squares. Despite this substitution, the illusory effect remains. (C) Variant in which the central shafts are missing. (D) The Müller-Lyer effect is also elicited by a figure comprising only dots.