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Essay On Blindsight

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4. Definition Blindsight is the phenomenon where individuals who are completely blind in some or all of their visual fields (the total area where objects can be seen as one’s eyes are fixed on a single point in space) are capable of detecting, localizing, or identifying a visual stimulus located in their affected visual fields despite denying that they see the stimulus (Cowey 2004). As the oxymoronic term suggests, blindsight has two components. When presented with a visual stimulus, patients report that they see nothing at all (blind) but when questioned about the stimulus (e.g. where it is or what it looks like), they answer correctly more often than not (sight). Blindsight does not occur in all blind patients, but in some who sustain damage…show more content…
Decades later, it was reported that four patients with damaged primary visual cortices were not consciously aware of visual stimuli presented to them but, when prompted to respond, moved their eyes towards the location of the stimuli (Poppel et al. 1973). The term blindsight was coined shortly thereafter in a report describing a patient with a surgically removed primary visual cortex (Sanders et al. 1974). Since then, many studies have investigated patients with blindsight using a variety of methods. 6. Characteristics Blindsight exists in two forms (Weiskrantz 1997); the patient either reports being completely unaware of the stimulus (type I) or is aware of the stimulus but does not acknowledge or experience that it is visual in nature (type II) . Besides direct reporting of responses, assessed by presenting a visual stimulus and asking the subject to choose from a set of options characterizing the stimulus (e.g. where it was or what it looked like), several other categories of responses to visual stimuli have been reported in blind humans and non-human primates. These indirect measures include hormonal changes, changes in pupillary and blinking reflexes, and the effects of processing of a stimulus in the affected visual field on the processing of stimuli in unaffected parts (Stoerig & Cowey 1997; Cowey
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