If you concentrate on a computer screen showing a swirling pattern of blue dots superimposed on some stationary yellow dots, the yellow dots will seem to wink in and out. But the erasing is happening in the mind, not on the computer screen — presented with contrasting stimuli, the brain has shifted into ‘winner takes all’ mode, sacrificing its attention to some aspects of the visual field.
This phenomenon — motion-induced blindness — probably happens a good deal in everyday life without our noticing it, say Yoram Bonneh, of the Smith-Kettlewell Eye Research Institute, San Francisco, and colleagues (Nature, Vol. 411, No. 6839, 14 Jun 2001). It illustrates how what we ‘see’ is in fact the result of the brain’s interpretation of imperfect sensory input.
Motion-induced blindness also reproduces some of the effects of the disorder simultanagnosia, where patients are unable to perceive more than one object at a time. These people frequently have damage to the parietal areas of their brains, and magnetic stimulation of this area also affects the occurrence of motion-induced blindness.
The website http://www.keck.ucsf.edu/~yoram/mib.html has demonstrations of motion-induced blindness.
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Message posted by: Trevor M. D'Souza