Neurosciences
Blind More Accurate at Judging Size Than Sighted
By American Psychological Society
Mar 29, 2005, 15:16

Researchers Melissa Smith, Elizabeth A. Franz, Susan M. Joy, and Kirsty Whitehead, of the University of Otago in New Zealand, found that "blind individuals were more accurate than sighted individuals in representing the size of familiar objects."

This research sought to examine the accuracy of memory representations by instructing participants to imagine a set of familiar objects (e.g., a can of soda, a loaf of bread, a carton of eggs) and then demonstrate the size of each object with their hands, without being able to see. Participants included both sighted individuals (who closed their eyes for the task) and blind individuals.

"Surprisingly, in over one hundred participants with normal vision, a marked overestimation in object size was demonstrated, suggesting that the visual-memory representations in sighted individuals might not be accurate after all," Franz said. Meanwhile, blind participants showed no overestimation and were more accurate in estimating object sizes.

The researchers argue that in people who are blind, the memory of familiar objects relies only on manual (not visual) representations that are based on their experiences holding the actual objects. In sighted individuals, however, memory of familiar objects relies on visual-memory representations. The authors believe visual representations may be inaccurate in size because "sighted individuals see objects everyday in different orientations and from different distances."

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