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PSYC 101 Chapter Notes -Corpus Callosum, Franz Mesmer, Split-Brain

Course Code
PSYC 101
Barbara Cox

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I. Consciousness as a Social Phenomenon
Can We Understand Consciousness?
Historically, 3 philosophical positions about nature of consciousness:
1. Consciousness is not a natural phenomenon, it is something supernatural, not to be understood by human
2. Consciousness is a natural phenomenon but we cannot understand it b/c of various reasons
Consciousness exists b/c of the nature of human brain but just how this occurs is not known
Our brains may not be simply able to understand biology of subjective awareness
Lack means to study it scientifically
3. People are conscious, this consciousness in produced by the activity of the human brain
Advocated by Donald Hebb
The Adaptive Significance of Consciousness
Consciousness is the awareness of mental processes, not the processes themselves
Consciousness is a characteristic that exists in addition to functions such as perception, memory, thinking &
planning so why do we need it?
Consciousness is a private experience that cannot be shared directly
We are not conscious of everything about ourselves
We are not equally conscious if the same thing all the time
Blindsight- ability to interact behaviourally with objects while remaining consciously unaware of them
Consciousness and the Ability to Communicate
Consciousness can be viewed as by-product of our ability to communicate symbolically
By using words or signs
Physiological basis is activity of the language mechanisms of the brain
Private use of language (thinking to oneself) is clearly conscious
Private non-verbal processes are conscious if we can describe them
We are conscious of external events only if we can think & verbalize about our perceptions of them
Provides us with self-awareness
Consciousness and the Control of Behaviour
Our perceptions may differ from the our actions towards external events
Our awareness of voluntary movements may reflect a by-product of other brain activities that initiate behaviour
II. Selective Attention
The process that controls our awareness of, & readiness to respond to, particular categories of stimuli or stimuli
in a particular location
Attention may be controlled automatically, controlled by instructions or controlled by demands of a particular
task we are performing
Attention to visual events tends to act like a spotlight or zoom lens that highlights the events within some
spatially contained area
Our attention mechanisms enhance our responsiveness to certain stimuli & tune out irrelevant info
We do not simply process all the info gathered by our sensory b/c brain mechanisms responsible for conscious
processing of info have limited capacity
Selective attention acts as the gatekeeper that controls the flow of info

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Auditory Information
Dichotic listening- task that requires a person to listen to one of 2 different messages being presented
simultaneously, one to each ear, through headphones
Shadowing- act of continuously repeating verbal material as soon as it is heard
First experiments on attention used dichotic listening & shadowing
Participants were made to pay attention to only the message they shadowed
The info that entered the unattended ear is lost within a few seconds unless something causes us direct
attention to it
Some info by its nature can break through into consciousness
Unattended info undergoes some verbal analysis
we are able to store info temporarily as it comes in
Filtration of the unattended info occurs after the sounds we hear are identified as words
Visual Information
Studies using visually presented info indicate that attention can focus on:
1. Location of the info
If a stimulus occurs where we expect it, we perceive it more quickly
If it occurs where we do not expect it, we perceive it more slowly
People can follow instructions to direct their attention to particular locations in the visual field
Mechanism of selective attention sensitizes neural circuits that detect visual stimuli in a particular region
2. Nature of the info (form or physical attribute of the info)
We can only watch one of 2 events happening closely & ignore the other
3. Meaningfulness of the info (its relevance to us)
Change blindness- failure to detect a change when vision is interrupted
o Show that we are more sensitive to relevant stimuli than to irrelevant ones so meaningfulness is
an important factor in attention
Inattentional Blindness- a failure to perceive an event when attention is diverted elsewhere
o Possibly b/c visual stimulation is so complex
o People often don’t see a change even when its blatant, once you can see it, you are astonished
how obvious it is
o It’s shocking how little of the world we actually perceive
o Missing the gorilla in the video! (50% of people do)
Brain Mechanisms of Selective Attention
Activity of particular regions of the brain is enhanced when people pay attention to particular characteristics of
visual stimuli
Found by brain imaging techniques
Why is consciousness wrong?
Many reasons….
For one thing, there’s a constant blind spot in your vision
Also, the image on your retina is 2D but you perceive the world in 3
The goal of conscious access isn’t truth, but usefulness-> not a camcorder, doesn’t have to be perfect
Usually there aren’t gorillas, your consciousness assumes stability in the world

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III. Consciousness and the Brain
Human consciousness is related to speech so then it is related to brain mechanisms that control
comprehension & production of speech
For us to be aware of a piece of info, the info must be transmitted to neural circuits in the brain
responsible for communicative behaviour
Supported by some cases of human brain damage
Brain damage can disrupt a person’s awareness of perceptual mechanisms without disrupting other
functions performed by these mechanisms
Isolation aphasia- a language disturbance that includes an inability to comprehend speech or to produce meaningful
speech without affecting the ability to repeat speech & to learn new sequences of words
Caused by brain damage that isolates the brain’s speech mechanisms from other parts of the brain
Appear to completely lose awareness of oneself & the environment
Ability to still repeat words & learn new words suggests that consciousness is not simply activity of
brain’s speech mechanisms
It is also activity prompted by info received from other parts of the brain concerning memories or events
presently occurring in the environment
Visual agnosia- inability of a person who is not blind to consciously recognize the identity of an object visually
Caused by damage to the visual association cortex
Not directly aware of one’s own visual perceptions
If pick up object, then can identify it
Visual system still works well enough to initiate appropriate non-verbal behaviours
Hands talk to you, telling you what you had just seen
Ex. cannot recognize object in picture is a gun, but hand makes movements of shooting a gun
Split Brain Syndrome
In people with severe epilepsy that cannot be controlled by drugs
Violent storms of neural activity begin in one hemisphere & are transmitted to the other by the corpus
Both sides of the brain engage in wild neural firing & stimulate each other, causing an epileptic seizure
Cutting the corpus callosum of the people to disconnect the 2 cerebral hemispheres reduces frequency of
seizures -> called split-brain operation
Normally, cerebral cortexes of left & right hemispheres exchange info through corpus callosum
Each hemisphere receives sensory info from the opposite side of the body & controls muscle movements on
that side
With exception of olfactory system
Person sniffing flower only through left nostril, only left brain receives sensation of the smell
Corpus callosum coordinates this so each hemisphere knows what is going on in the other
When the 2 hemispheres are disconnected, they operate independently, cannot exchange info
A person with split brain can make perceptual judgements with right hemisphere but he are she cannot talk
about them & appears to be unaware of them b/c the left hemisphere controls speech
Split brain patients also report that their left hand seems to have a mind of its own
Effects of cutting the corpus callosum reinforce that consciousness depends on ability of speech mechanisms in
left hemisphere to receive info from other brain regions
If this communication is interrupted as in split brain patients, some kinds of info can never reach consciousness
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