Effects of gap size between shaft and fins and of angle of fins on the Müller--Lyer illusion.
Assimilation theory was employed to generate quantitative predictions relating the ingoing Müller--Lyer illusion to both angle of fin and gap between shaft and fin. Gap sizes were varied from zero to 18 mm in steps of 2 mm, and angles of fins were varied from 30 degrees to 180 degrees in steps of 30 degrees. Five subjects adjusted the length of a comparison line to match the apparent length of the shaft at each combination of gap size and angle of fin. It was predicted that the gap necessary for a reversed illusion to occur, and the gap at which the maximal reversed effect occurred, would be inversely related to angle of fins. Empirical functions verified the predictions.
D006801:Humans; D007088:Illusions; D008297:Male; D009903:Optical Illusions; D009949:Orientation; D012858:Size Perception; D013028:Space Perception