The Muller-Lyer figure and the fly

In the Muller-Lyer illusion two horizontal line segments of equal length are perceived by humans as unequal. The gaze of a fly presented with Muller-Lyer figures corresponds to human eye movements and human (illusionary) evaluations of the segment lengths. It is suggested that a theory similar to the phenomenological theory which accounts for the fly's gaze may account for the human eye's movement during an observation of Muller-Lyer figures