Shape completion time depends on the size of the occluded region

Observers made speeded discriminations of whole, occluded, and mosaic shapes. Shape matching times increased with the amount of occluded shape (Experiment 1), as did the time to merely discriminate 2 shapes (Experiments 2-4). By contrast, the time to judge the shape of the visible portion decreased with larger occluded regions (Experiments 5-7). Experiments 3 and 6 used motion parallax to show that different perceptual operations are involved in discriminating occluded versus mosaic shapes. Experiments 4 and 7 showed that shape completion was unaffected by spatial attention. Results suggest that shape completion is a rapid and obligatory aspect of perception. However, they also show that the time course of completion varies with the size of the hidden region.