The phenomena described above are “low-level” illusions that are probably based on “bottom-up” sensory signals from brain cells in the visual system that are specialized to detect motion. Normally, sensory information agrees. If a cat is partly hidden behind a tree, for example, all the cues of color, shadows, and texture tell the same story—that the hidden part of the cat exists out of view behind the tree. The brain acts like a judge, confirming the same story as told by independent witnesses. The brain also strengthens this verdict with “top-down” information based upon prior learning: if the cat’s whiskers stick out on one side of the tree, and its tail on the other, the brain automatically “fills in” that there is a continuous cat partly hidden by the tree, not two unrelated cat bits. This interpolation process, called visual amodal completion, starts from a representation of the visible features of the stimulus in early visual cortex, probably an area called V1, and ends with a completed representation of the stimulus in the inferior temporal cortex.9 Jay Hegdé of the University of Minnesota and colleagues even found two regions in the object-processing pathways of t
While Dr. Anstis' research interests lie in visual perception, we can certainly apply his insights to witness evidence. Did that eyewitness see what she thinks she saw?