Rebecca Lawson, University of Liverpool

Heinrich H. Bülthoff, Max Planck Institut für biologische Kybernetik

Sarah Dumbell, University of Liverpool

Four experiments are reported in which pictures of different morphs of novel, complex, 3-D objects, similar to objects which we must identify in the real world, were presented. We investigated how changes of viewpoint influence our ability to discriminate between morphs. View changes had a powerful effect on performance in picture ^ picture matching tasks when similarly shaped morphs had to be discriminated. Shape changes were detected faster and more accurately when morphs were depicted from the same rather than different views. In contrast, view change had no effect when dissimilarly shaped morphs had to be discriminated. This inter- action between the effects of view change and shape change was found both for simultaneous stimulus presentation and for sequential presentation with interstimulus intervals up to 3600 ms. The interaction was found after repeated presentations of the stimuli before the matching task and after practice at the matching task as well as after no such pre-exposure to the stimuli or to the task. The results demonstrate the difficulty in activating abstract, view-insensitive represen- tations to help to achieve object constancy, even when matching over long interstimulus intervals or after stimuli have already been seen many times.

Perception, (2003), 32, 1465-1498