# PERCEPTUAL CONSTANCY AND APPARENT PROPERTIES Keith Allen **Opening (not a real abstract):** Keith Allen, University of York November 2011 Properties like shape, size and colour exhibit perceptual constancy. As a first approximation, a property exhibits perceptual constancy if there is some sense in which objects instantiating the property ‘look’ or ‘appear’ the same as the perceptual conditions vary. Perceptual constancy is a puzzling phenomenon, however, because as the perceptual conditions vary, there is also some sense in which objects ‘look’ or ‘appear’ different. For example, there is some sense in which a penny tilted in space looks the same as a penny presented perpendicular to the line of sight—both look round. Yet there is nevertheless some sense in which the tilted penny looks different to the penny seen face-on—it appears elliptical. Likewise, a cow in the distance looks in some way the same as, and yet