Occlusion, Illusion and Spatiotemporal Fusion

Evan M. Palmer, Ph.D.
Visual Attention Laboratory
Brigham & Women's Hospital
Harvard Medical School

Many objects in the environment are partially occluded by other  
objects, causing their images to be fragmented on the eyes.  When  
objects or observers move, the patterns of occlusion can change  
dramatically, causing shape information to be fragmented in both  
space and time.  However, we tend to handle these visual situations  
with relative ease.  How does the human perceptual system collect and  
utilize spatiotemporally fragmented shape information to arrive at  
accurate visual representations of objects?  I will present data  
showing that when an object is seen through an occluding surface with  
many apertures, perception is quite accurate.  However, when an  
object is seen through only two apertures, a robust visual illusion  
occurs. These seemingly contradictory findings can be reconciled  
using the theory of Spatiotemporal Relatability, which provides a  
framework for understanding perception of dynamically occluded objects.