PSYA01H3 Chapter Notes - Chapter 9: Visual Agnosia, Auditory Cortex, Inattentional Blindness

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Published on 12 Apr 2013
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Can we Understand Consciousness
Historically people taken three positions on consciousness: not natural phenomenon (miracoulous, not
understandable by human mind), natural phenomenon we can’t understand (exists because of nature of brain, but
how is unknown), and thirdly people are conscious and its produced by brain activity, and it can be explained
Hebb believed the third one
The Adaptive Significance of Consciousness
Consciousness is awareness of perceiving, remembering, thinking, not those itself
Consciousness does not exist, humans exist with the ability to be conscious
Consciousness is private experience, cannot be shared directly, we experience our own consciousness and infer
others being conscious because they are like us and because they tell us they are conscious
Consciousness is not general property of all parts of brain (not conscious of everything about ourselves or equally of
one thing all the time)
Blindsight: ability to interact behaviourally with objects while remaining consciously unaware of them
Caused by damage to visual cortex or pathway leading to or from that area
Able to reach for a cane and grab it although they are unable to be conscious of it being there
Consciousness is primarily social phenomenon, awareness through communication, and selfawareness through inner
Consciousness and the ability to Communicate
Able to translate private events into symbolic expressions; brain mechanisms for communicating receive input from
systems of brain involved in perceiving, thinking, remembering and so on
Our words have effect on other peoples thoughts, perceptions, memories and behavior
Ability to communicate with ourselves symbolically gives rise to consciousness
Cheesman and Merikle presented people with word (prime) that was congruent or incongruent with a patch of color
(target) and asked to name the color of the patch, which is difficult when prime is incongruent. If add mask
immediately in front of prime, participants unconscious of the meaning of the prime, but it still affected the naming
of the color if incongruent
Tried where pretty much all congruent, but with mask, unable to predict which color would come up and name it
Consciousness has this property: we become able to describe, and use, the psychological events that are private to
Consciousness and the Control of Behaviour
James suggests emotional awareness comes after a reaction, scared because we tremble, etc.
Vertical crayon seems longer than horizontal but it does not affect our action to go grab them in terms from end to
Thus perceptual awareness of objects may be based on different visual system than the one we use for actions
Ebbinghaus illusion same size coin surrounded by smaller or larger circles
Introspective experiences tell us coin sizes are different, behaviour reflects otherwise
Libet timed a hand motion while participants watch rapidly moving clock hand. They were to report where clock
hand was at time they became aware of intention to move. Indicated electrical brain activity of motor cortex
activated 7/10 of a second before the motion, and the intent to move was aware 3/10 of a second before motion, and
then motion
Obhi experiment: pressing on a keyboard un/intentionally, awareness of movement, even when intentional was
based on sensory feedback from finger
Selective attention: process that controls our awareness of, and readiness to respond to, particular categories
of stimuli or stimuli in a particular location
Process determines what information we become conscious of
Can be controlled automatically (loud sound catches attention), instructions, demands of particular task we are
To enhance responsiveness to certain stimuli and ignore irrelevant info
Broadbent we don’t just process all info being gathered because brain mechanisms responsible for conscious
processing are limited in capacity.
Auditory Information
Cherry devised dichotic listening: a task that requires a person to listen to one of two different messages being
presented simultaneously, one to each ear, through headphones
Asked to shadow (act of continuously repeating verbal material as soon as it is heard) one message, which
ensures focus on one message
People did not notice what the other ear message was or even if it switched to foreign
The unattended sensory channel is not just turned off, people would still hear their name in an unattended ear or if
there are sexually explicit words people tend to notice immediately
This means even unattended info goes through verbal analysis, if filtered out, it is after they are analyzed as words
McKay found that words spoken to unattended ear affected interpretation. (they threw stones toward the bank
yesterday, hearing river or money, then asked if they heard side of river or savings and loan association) of course
they heard neither but their answer was determined on the unattended ear
There is temporary storage of unattended info, ex. When busy and asked question you ask what but answer before it
is repeated
Treisman people can shadow message even if it switches ears
This is useful in crowded places trying to focus on one conversation
Visual Information
Studies show that we can successfully attend to location nature and meaningfulness of information
Location of Information
Snyder, Davidson, Posner, people watch screen to detect letter, arrows either point where letter will be, opposite, or
a neutral plus.
Faster to response when notified correctly than incorrectly
If stimulus occurs where expected, perceive it quickly, opposite is opposite
Nature of Information
Two events can happen in close proximity but we can watch one and ignore the other
Neisser and Becklen showed participants overlapping images, one of bloody knuckles, one of basketball ,
participants could remember what happened in one scene but not attend to both
The Meaningfulness of the Information
Simon thought visual field rich in info, ability to represent it in memory is limited
Change blindness: failure to detect a change when vision is interrupted by a saccade or artificially produced
When we fail to attend to feature we don’t encode it and can’t recognize it when it changes
Pearson and Schaefer showed picture and picture with changes (picture involved driving) features more
meaningful to the overall scene are attended to
Cultural background also affects attention in change blindness; Japanese more sensitive than Americans to changes
in part of a picture that describes context
Simon and Levin showed people who give directions to someone won’t notice change about that person in brief
obstruction because they are attending to directions not the person
Inattentional blindness: failure to perceive an event when attention is diverted elsewhere
Simon and Chabris - Example of gorilla in basketball game, people didn’t notice though in centre of action. People
more likely to see if it is woman with umbrella for pure possibility, gorilla seems really unlikely
Similarity of unexpected event with things we attend to that determine inattentional blindness
Brain Mechanisms of Selective Attention
Some components of brain sensory system are temporarily sensitized which enhances ability to detect particular
categories of stimuli, (i.e. watching shapes, focused on color, part of visual cortex devoted to the analysis of it will
be increased in activity)
Corbetta showed screen with 30 color rectangles that could change in shape, colour or speed, participants asked to
say if change detected. Some trials attention only to be paid to one attribute.
PET scanner on brains showed different areas for different attributes being activated
Brain damage can alter one’s consciousness, ex of anterograde amnesia, cannot form verbal memories but can learn
some tasks, does not prevent all kinds of learning but prevents conscious awareness of what has been learned
If human consciousness related to speed, probably related to brain mechanisms that controls comprehension and
production of speech
This suggests for us to be aware of a piece of info, it must be transmitted to neural circuits in brain responsible for
neural behaviour, several cases of brain damage supports this
Isolation Aphasia: A Case of Global Unawareness
Geschwind, Quadfasel, Segarra woman suffered brain damage from carbon monoxide inhalation, spared primary
auditory cortex (speech area of brain) and connections between these areas BUT damaged destroyed large parts of
visual association and isolated speech mechanisms from other parts of brain
Isolation aphasia: language disturbance that includes inability to comprehend speed or produce meaningful
speech without affect ability to repeat speech and learn new sequences of words; caused by brain damage that
isolates brain’s speech mechanisms from other parts of brain
Woman in hospital for 9 years gave no evidence of recognizing objects or people in environment, eyes could still
move around, not spontaneously say anything, answer, or give any signs that she understood what people said to
her, by all criteria, not conscious of anything going on
BUT she could repeat what was said to her and if they started a poem she knew, she would finish it
She could also learn new songs and poems and would sing along with radio
Suggests consciousness is not just brain’s speech mechanisms; it is activity prompted by info received from other
parts of brain concerning memories or events presently occurring
Visual Agnosia: Lack of Awareness of Visual Perceptions
Visual agnosia: inability of a person who is not blind to recognize the identity of an object visually cased by
damage to visual association cortex
Though cannot visually identify object, the patient’s hand can still recognize and make appropriate movements like
when shown pistol, hand would make motion of a pistol and firing it, though he could not say what it was yet
Once felt what he was doing, could name object
Loses ability to read but by learning deaf alphabet, was able to, by feeling the movements his hands made when
reading, very slowly read
Unaware of own visual perceptions, his hands talked to him telling him what he had seen