Diamond-winged variants of the Müller-Lyer figure: a test of Virsu's (1971) centroid theory.

Diamond-winged variants of the Müller-Lyer figure were used to test predictions of Virsu's (1971) theory of the Müller-Lyer illusion based on efferent readiness for eye movements toward the figure's center of gravity. A Müller-Lyer figure with diamond-shaped wings resulted in a greater center-of-gravity distance than the corresponding, conventional Müller-Lyer figure, but fin length and the rest of the figure remained constant; in Virus's study, fin length and center-of-gravity distance covaried. Results were consistent with Virus's data when we used the stimulus conditions that he reported. Results from a wide range of stimuli challenge Virsu's theory, and thus are consistent with the conclusions of Brigell, Uhlarik, and Goldhorn (1977).