Thesis defense Sven Vrins (Donders Series 84)

28 March 2012

Promotor: Prof.dr. H. Bekkering, copromotor: Dr. R. van Lier

Shaping Object Boundaries: contextual effects in infants and adults

The process of visual perception begins as soon as light, reflected from an object in our environment, falls onto our retina. Within a few hundred milliseconds, our visual system creates a mental representation of that object, reveiling (among other properties) its shape and color. Still, the information at the retinal level is often (if not always) incomplete and fragmented, due to (for instance) partial occlusion of one object by another. Interestingly though, viewers experience objects in their environment as complete. Apparently, when building mental representation of partly occluded objects, our visual system “fills in” the invisible parts – a process dubbed amodal completion. Past research has demonstrated how contour properties of the visible parts of partly occluded objects play an important role during amodal completion in adults. The present experiments show that young infants also complete partly occluded objects (in 2D and 3D). However, unlike in adults, the completion process seems dominated by local information processing, rather than global information processing. Despite the dominance of global object information processing in adults, an effect of knowledge (as part of global object characteristics) was never found. However, the current experiments show that knowledge can play a role during amodal completion in adults. Counter-intuitively, this effect is present in early, rather than late stages of perception, suggesting a rapid feed-forward sweep of visual information that affects amodal completion.