An analysis of the phenomenon of blindsight provides an advanced understanding of
human consciousness and also has implications for decision making. Past
experimentation involving blindsight created some of the first scientific evidence for
automatic processing. This evidence contradicted the once prevalent notion that
sense perceptions must enter consciousness in order to affect behavior.
The human brain contains multiple mechanisms, many of which can function
simultaneously, allowing it to perform many complex operations smoothly and
efficiently. There are multiple systems involved in vision. I am sure that you can
imagine that humans have pretty advanced visual systems as vision proves to be one
of the most important sensory components in day to day life.
Scientists like L. Weiskrantz have been able to distinguish two of our visual systems
from one another. Weiskrantz and his group, who created the term “blindsight”,
administered sight tests to people who were brain damaged. The subjects were
normal except for the fact that the damage that they sustained left them blind in large
parts of their visual fields. When a person damages the visual system on a certain
side of their head it produces blindness in the visual field on the opposite side of the
body. For example a person who damages their right brain will be blind to everything
to the left when they are looking straight ahead.
Weiskrantz and other researchers have found that when an object is placed in an
individual’s blind field, they report that they are not able to see it, yet they can reach
for it and grab it with uncanny accuracy. The subjects seem surprised and cannot
explain how they were able locate the object after they began to reach for it. They
were able to grab the object because their efforts were aided by a visual system that
does not interact directly with the conscious mind.
A great deal of our movement and thought is not regulated by the conscious mind. It
is processed unconsciously, so that we do not have to think about it, and can let our
conscious mind devote its time and energy to the more difficult operations. After you
repeat an action a certain number of times, it becomes second nature to you. The
unconscious works in unison with the conscious to produce complex thought, actions
When humans react to physical stimuli, the sensory and motor areas of the brain
become electrically active. When we think to ourselves and perform complex mental
operations, a different area of our brain becomes active. This area is the prefrontal
cortex and it is thought to be the area most responsible for higher cognitive
processing and consciousness. The human prefrontal cortex is actually much larger
than that of other animals.
Because evolution is the gradual process of adding to and refining an organism, we
find that the more complex animals retain many of the fundamental traits of their
ancestors. The visual system that allowed the blindsight subjects to locate the object
in their blind field is in fact an evolutionary remnant of our early ancestors.
Amphibians and reptiles were our first ancestors to emerge from the ocean. They
developed sensory systems much different from the fish that they came from in order
to deal with life on the land. Frogs, lizards and other reptiles do not engage in a great
deal of conscious analysis before they act. The vast majority of their behavior comes
in the form of automatic responses. The more simplistic an animal’s intelligence the
less it deliberates and the less free will it exercises.
This reptilian visual system is probably responsible for the movements that are
automatic for us as well. Normally all of our neural systems work together
synchronously and we will not be able to distinguish our unconscious reactions from
our conscious ones. In the case of blindsight though, the damage to the subject’s
brain created a schism between the conscious and the unconscious, which was able
to be observed by researchers.
There are actually several phenomena that are neurologically analogous to blindsight,
1. Blindness Denial: There are cases of brain-damaged people who are blind but
who are not aware of the fact that they are blind, and they report that they can see
2. Jargon Aphasia: There are cases of brain-damaged people who speak
completely unintelligibly but are not aware of it.
3. Oral/ Verbal Dissociation: There are cases of brain-damaged people who
cannot orally tell you what you just told them, but they can write it down correctly.
Furthermore, they cannot report memory of what they just wrote or what it refers to.
|Organization for the Advancement
of Interdisciplinary Learning