11
December 2003
Perception: Getting a grip on shapes
Vision is an astonishingly powerful tool by which we perceive and ultimately influence our environment. But our eyes alone can easily be misled: a tall tower is likely to appear narrower than a squat building of the same width, for example. If we relied on the accuracy of simple perception when exerting visual control of action, we might find it hard to grasp a computer mouse let alone perform tasks as complex as driving a car. That we do have a two-tier view of the world is confirmed by experiments reported this week. Volunteers were challenged to grasp a rectangular block. When they looked at the block, they could not ignore its length when judging its width. But when they grasped that same block in their hands, across its width, its length was irrelevant. This shows that passive perception involves 'holistic' processing of all aspects of an object's shape, but when vision is used to direct physical engagement with an object, only the relevant information on size and shape is used.
Visual control of action but not perception
requires analytical processing of object shape
TZVI GANEL & MELVYN A. GOODALE
Nature 426, 664–667 (2003); doi:10.1038/nature02156
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