Does the Mueller-Lyer Illusion Include the Misperception of Egocentric Location?

The reported absence of egocentric localization errors when pointing open-loop at the vertices of the Mueller-Lyer (M-L) illusion figure was confirmed in several studies which were designed to ensure the normal strength of the illusion during the pointing responses. However, when one of the two 'fins' was removed, the resulting M-L figure was substantially mislocalized. A theory of the expanding and contracting spatial effects of fins is proposed to explain these results.