Blindsight

17701365

Garth Fernandez

Analytical Essay 1
The phenomenon of ‘blindsight’ is much discussed, but little understood.
What does ‘blindness’ really mean in the context of blindsight?

Blindsight is defined as the ‘visual capacity in a field defect in the absence of acknowledged
awareness’ (Overgaard, 2012). Philosophically, blindsight has been thought of as part of the natural
depth of consciousness by Colin McGinn (1991) but this essay will pertain to the neurological and
psychological aspects of this occurrence. Blindsight is an abnormal psychological phenomenon in
which some patients who have suffered abrasions to their primary visual cortex (or V1) in the
occipital lobe, and are consequently cortically blind, to still be able to respond to visual stimuli that
they cannot consciously observe (Weiskrantz, 1986.)

Case studies testing this phenomenon are usually conducted on patients who experience on
an isolated side of their visual field where they are presented with a stimulus on their blind side and
are asked to discriminate in a forced-choice task. The research by Weiskrantz (1986) shows that
despite the patient reporting total blindness in that area they still report an accuracy that is high then
chance. This would imply that the removal of conscious experience does not necessarily result in a
complete disturbance in the functional flow of information to and from the brain. As discussed in
Weiskrantz (1997) blindsight can be present in two forms. When a subject is able to distinguish, at a
level significantly above chance, aspects of a visual stimulus with no conscious awareness, they
exhibit Type 1 blindsight. However, when the subject can notice in a general change falling within
they blind area (such as movement) but that it was not visual perceived, they exhibit Type 2
blindsight. Therefore it can be difficult in determining what exactly constitutes “blindness” in a
person.
101678- Motivation and Emotion

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