The Effect Of Fin Length Changes On Apparent Shaft Length And Depth In The Muller-Lyer Illusion

Muller-Lyer figures with outgoing fins were back illuminated and shaft length and depth were both judged. With the angle between the fins constant, progressive increases in fin length produced first an increase in the apparent shaft length and then a decrease. Changes in fin length, however, had no significant effect on apparent depth. These data were interpreted as inconsistent with an account of the Muller-Lyer illusion in terms of perspective theory, since the latter predicts systematic changes in perceived shaft length to be associated with systematic changes in perceived depth.