Non-veridical size perception of expanding and contracting objects

Observers were presented with various types of stimulus expansion and contraction which resulted in marked misperceptions of size. Firstly, the perceived size of an object which is changing in size is shown to be biased in the direction of the size change. Secondly, expansion or contraction of the internal texture of objects is found to influence their perceived size. Finally, an illusory texture manipulation in the form of a movement after-effect is shown to produce the same type of size misperception as a real expansion or contraction of internal texture. The spatio-temporal characteristics of these illusory size changes are investigated.