Test of Gregory's Constancy Scaling Explanation of the Müller-Lyer Illusion

MUCH of the recent interest in geometrical illusions has centred on a size constancy explanation by Gregory 1–3 . Size constancy occurs when the apparent size of an object remains constant, independent of the distance of the object from the observer, even though the size of the retinal image varies with the distance. The mechanism which produces size constancy has been called constancy scaling 2 .