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Chapter 9

Chapter 9- Consciousness.doc

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University of Toronto Scarborough
Steve Joordens

Chapter 9- Consciousness Consciousness as a Social Phenomenon • Years ago, psychologists denied that there was anything to explain in consciousness and that it was not behaviour Can We Understand Consciousness? • People have taken 3 philosophical positions about the nature of consciousness: o Consciousness is not a natural phenomenon (laws involving matter and purely physical forces)  Sometimes supernatural and miraculous, not to be understood by the human mind o Consciousness is a natural phenomenon, but also that, for various reasons, we cannot understand it  Exists because of the nature of the human brain, but just how this occurs is unknown  Some say we can never understand consciousness because our brains are not capable of doing so  Others say that we are probably capable of understanding consciousness but that at present, we lack the means to study it scientifically o People are conscious, that this consciousness is produced by the activity of the human brain, and that there is every reason for us to be optimistic about our ability to understand this  Advocated by Donald Hebb, who stated that “consciousness, a variable state, is a present activity of thought processes in some form and thought itself is an activity of the brain” The Adaptive Significance of Consciousness • Consciousness is the awareness of these processes (perceiving, remembering or thinking), not the processes themselves o Consciousness is a characteristic that exists in addition to functions such as perception, memory, thinking, and planning • “Consciousness” does not exist but other people are conscious because they are like us and they can tell us that they are also conscious • We are not conscious of everything about ourselves, nor are we equally conscious of the same thing all the time • Consciousness is not a general property of all parts of the brain Blindsight- the ability to interact behaviourally with objects while remaining consciously unaware of them 1 • Caused by damage to the visual cortex, or to some of the pathways leading into or from that area • A part of the visual system can control our ability to react to the presence of objects, directing our eye movements, our limbs, and other behaviours, but without necessarily giving the info needed for us to describe or to think about the objects • The explanation of consciousness lies in its relation to deliberate, symbolic communication which our ability provides with self-awareness Self-awareness- built on inner speech, which allows us to describe our behaviours and compare them to others Consciousness and the Ability to Communicate • We can express our needs, thoughts, perceptions, memories, intentions, and feelings to other people • Accomplishments require 2 general capacities: o Must be able to translate private events- our needs, thoughts, and other processes- into symbolic expressions  The brain mechanisms we use for communicating with others must receive input from the systems of the brain involved in perceiving, thinking, remembering, etc o Our words and other symbols must have an effect on the person listening  Must affect the listener’s own thoughts, perceptions, memories, and behaviour • We are all capable of expressing out thoughts symbolically and of decoding the symbols that other people express, which enables us to communicate with ourselves, privately • The ability to communicate with ourselves symbolically gives rise to consciousness • Cheesman and Merikle found that conflicting primes produce a Stroop- like interference even when the mask (a random jumble of letters) interfered with the conscious ability to identify the meaning of the prime (the word) • Behaviour of animals viewing mirror images suggest that some primates may have a concept of self-awareness Consciousness and the Control of Behaviour • Many found it pointless to explain something that we could observe (behaviour) in terms of something that we could not (consciousness) • Rene Descartes believed that human actions were controlled by a non- material mind, but his dualism was not a productive way of explaining behaviour 2 • William James proposed that our emotional awareness comes after a reaction • Goodale have evidence that our actions are little affected by such visual illusions • Our perceptual awareness of objects may be based on a different visual system than the one we use for actions • The conscious thought and the action are both caused by a third action of the brain • Libet discovered the brain starts the movement before there was awareness of “willing” the motion • When awareness was late, the lateralized readiness was late, when awareness was early, the lateralized readiness was early • The brain must “bind together” the experience of voluntary movement with its external consequences Selective Attention Selective attention- the process that controls our awareness of, and readiness to respond to, particular categories of stimuli or stimuli in a particular location • Determines which events we become conscious of • Attention may be controlled automatically, by instructions, or by demands of the particular task we are performing • Our attentional mechanisms serve to enhance our responsiveness to certain stimuli and to tune out irrelevant info • The storage of info in implicit memory does not require conscious attention • The brain mechanisms responsible for conscious processing of info have a limited capacity, so we need some system to serve as a gatekeeper, controlling the flow of info to this system Auditory Information 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 Shadowing- the act of continuously repeating verbal material as soon as it is heard • Ensures that the listener pays attention to only that message • Info that had entered the unattended ear would appear to be lost because a channel of sensory input can simply be turned off • Some info, by its very nature, can break through into consciousness because some kinds of info presented to the unattended ear can grab 3 our attention indicates that even the unattended info undergoes some verbal analysis • The info, held in temporary storage, was made accessible to your verbal system • Even though an unshadowed message cannot be remembered later, it produces some trace that can be retrieved if attention is directed to it soon after the words are presented • Able to listen to someone over other conversations, hard to strain out the cross-conversation if it’s more interesting Visual Information • Can attend to the location of the info, to the nature of the info (revealed by its physical features), and to the meaningfulness of the info (its relevance to our interpretation of what we’re seeing) Location of the Information • When correctly informed of the location of the stimulus  responded faster • When incorrectly informed of the location of the stimulus  responded slower • If a stimulus occurs where we expect it, we perceive it more quickly • If a stimulus occurs where we do no expect it, we perceive it more slowly • Neural circuits that detect a particular kinds of stimulus are somehow sensitized, so that they can more easily detect that stimulus The Nature of the Information • 2 events happen in close proximity, but we can watch one of them while ignoring the other The Meaningfulness of the Information • The ability to represent our visual experience in memory may be limited Change blindness- failure to detect a change when vision is interrupted by a saccade or an artificially produced obstruction • Inability to remember a scene in its entirety • A feature that is more meaningful to the overall scene is attended to Inattentional blindness- failure to perceive an event when attention is diverted elsewhere Brain Mechanisms of Selective Attention 4 • Paying attention to shape, colour, or speed of movement caused activation of different regions of the visual association cortex • Neurons that received input from the appropriate part of the visual field began firing more rapidly, even before the stimulus was presented Consciousness and the Brain • The brain damage does not prevent all kinds of learning, but it does prevent conscious awareness of what has been learned • If human consciousness is related to speech, then it is probably related to the brain mechanisms that control comprehension and production of speech Isolation Aphasia: A Case of Global Unawareness Isolation aphasia- a language disturbance that includes an inability to comprehend speech or to produce meaningful speech without affecting the ability to repeat speech and to learn new sequences of words • Caused by brain damage that isolates the brain’s speech mechanisms f
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