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Chapter 9

Chapter 9

13 Pages

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PSYC 100
Meredith Chivers

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Week 10: Chapter 9: Consciousness pp. 264-293 Consciousness as a Social Phenomenon Can We Understand Consciousness? - 3 philosophical positions about the nature of consciousness: not a natural phenomenon, it is not subject to laws of nature it is something supernatural and can’t be understood by the human mind a natural phenomenon, but we can’t understand it exists because of the nature of the human brain (we don’t know how) produced by activity of the human brain; we have ability to understand it Hebb: “consciousness, a variable state, is a present activity of thought processes in some form; and thought itself is an activity of the brain” Hebb said consciousness is not just neural impulses, but if we understand the neural level, it would help us with our understanding of the psychological concepts The Adaptive Significance of Consciousness - consciousness is the awareness of complex mental processes (perceiving, remembering, thinking), not the processes themselves consciousness is a characteristic that exists in addition to functions like perception, memory, thinking, planning - consciousness is a private experience and can’t be shared directly we can only experience our own consciousness - we aren’t 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 - ie. blindsight: the ability to interact behaviourally with objects while remaining consciously unaware of them caused by damage to the visual cortex or pathways related to it person will reach for a cane, even though they can’t see it part of our brain gives us ability to react to the presence of objects, direct our eye/limb movements w/o giving us info to describe/think about the object - for other parts of the brain, awareness comes with some effort ie. when we’re trying to concentrate on something with concentration, we can then describe these activities of the brain so as to convey them to other people - main evidence of consciousness in other people: through the use of language explanation for consciousness is in its relation to deliberate, symbolic communication ability to communicate, provides us with self-awareness, thus self-awareness is built on inner speech (lets us describe our behaviours and compare them to others) thus, consciousness is a social phenomenon Consciousness and the Ability to Communicate - we can express needs, thoughts, memories, perceptions, feelings, etc. to other people - these accomplishments require 2 general capacities: we have to be able to translate private events into symbolic expression brain mechanisms used to communicate w/ others must receive input from the systems of the brain that have to do with perceiving, thinking, etc. our words must have an effect on the person listening once words are decoded in person’s brain, they must affect their own thoughts, perceptions, and ultimately, their behavior ie. if we describe an event we witnessed, listener will be able to imagine the event (episode will become part of listener’s memory) - we communicate with ourselves privately, we think words - thinking in words involves subvocal articulation, thus, the brain mechanisms used to understand and produce speech, are the same mechanisms used to think words - ability to communicate with ourselves symbolically gives rise to consciousness we are conscious of those private events we can talk about (to ourselves or to others): our perceptions, needs, intentions, memories, feelings - the new special condition: there were many more congruent than incongruent primes so by using a prime, one could predict what colour was about to come - when the person was conscious of the prime-> they used the predictive information of the prime - when the person was not conscious of the prime-> they couldn’t use this prediction Consciousness and the Control of Behaviour - Descartes’ viewed all human actions were controlled by a non-material mind (dualism) - William James proposed contrasting idea: our emotional awareness comes after a reaction ex. we feel sorry because we cry, afraid because we tremble his theory is an alternative way to think about consciousness - recent evidence from cognitive psychology and neuropsychology gives way of thinking about issue of conscious control of behaviour some of this evidence uses visual illusions - there is evidence that our actions are little affected by such visual illusions - the visual system we use for our perceptual awareness of objects may be based on a different visual system than the ones we use for our actions Ebbinghaus illusion, small circle surrounded by multiple circles vs. large circle sourrounded if the circles were objects and we reached for them, our behaviour would be unaffected by the difference in relative size our introspective experiences might tell us that the two circles are different, but our behaviour says otherwise Selective Attention - we are not conscious of all the stimuli detected by our sensory organs ex. if you’re looking at a fish, you won’t be conscious of the chirping birds, rustling leaves, etc. - selective attention: the process that controls our awareness of, and readiness to respond to, particular categories of stimuli or stimuli in a particular location the process that controls our awareness of particular categories of events in the environment process of selevtive attention determines which events we’re conscious of attention can be controlled: automatically: when an intense stimulus captures our attention ie. loud sounds by instructions: ie. “pay attention to that one over there!” by demands of the particular task we’re performing ie. when driving, pay special attention to things like road signs, other cars - our attentional mechanisms serve to enhance our responsiveness to certain stimuli and to tune out irrelevant information - attention plays a strong role in memory controls the info that reaches short-term memory, ultimately determining what info is stored in explicit long-term memory (storing implicit memory doesn’t require conscious attention) - selective attention exists: according to Broadbent, because the brain mechanisms involved in conscious processing of this info have a limited capacity selective attention serves as a gatekeeper, controlling the flow of info to this system Auditory Information - selective attention test was devised, called dichotic listening dichotic listening: task that requires a person to listen to one of two different messages being presented simultaneously, one to each ear, through headphones participants had to shadow message presented to one ear, to ensure they would pay attention to only that message shadowing: the act of continuously repeating verbal material as soon as it is heard info that entered the unattended ear appeared to be lost, people said they heard something, but they didn’t know what it was suggested a channel of sensory input (in this case, one ear) could be turned off some kinds of information presented to the unattended ear still grab our attention (ie. our name, sexually explicit words) showing that all information goes through verbal analysis if the unattended information is filtered out at some point, it happens after the sounds were identified as words - we’re able to notice and remember some info received by the unattended sensory channel and store that information temporarily, as it comes in ie. you’re preoccupied and realize someone asked you a question, but you don’t know what was asked before they repeated the question, you answered it bc. you remembered the question the info was held in temporary storage and was made accessible to your verbal system - selective attention has practical significance ex. if we’re talking to someone in a room full of other people having conversations, we can actually sort out one voice from another, which is called the cocktail party phenomenon Visual Information - many experiments showed that we can attend to the location of the information, to the nature of the information (revealed by form or colour), and to the meaningfulness of the information Location of the Information - studies on sensory memory showed the role of attention in selectively transferring visual information into verbal short-term memory - selective attention can affect the detection of visual stimuli if a stimulus occurs where we expect it, we perceive It more quickly thus, people can follow instructions to direct their attention to particular locations in the visual field - neurologically: neural circuits that detect a particular kind of stimulus are somehow sensitized so that they can detect that stimulus more easily - in this case, the mechanism of selective attention sensitized the neural circuits that detect visual stimuli in a particular regions The Nature of the Information - second dimension of visual attention is the nature of the object being attended to - when two events are in close proximity, we can watch one of them and ignore the other The Meaningfulness of the Information - our visual experience is rich with information, but our ability to represent it in memory may be limited - if visual displays are changed during a saccade or a disruption, change blindness could happen - change blindness: failure to detect a change when vision is interrupted by a saccade or an artificially produced obstruction ie. look at picture 1 and try to remember everything, flip page and look at picture 2, try to find the difference between the two flipping page was the disruption, so person won’t notice the difference - change blindness reflects our inability to remember a scene in its entirety - when we don’t attend to a feature, then we don’t encode it and can’t recognize when it changes ex. if we don’t notice that there was a crosswalk in the first picture, we don’t notice that it moved - experiment: looked at the role of meaningfulness I change blindness - they had 2 pictures, that were only different by one feature - they are pictures of a scene seen by a person driving a car - finding: when driving-relevant features changed, they were spotted more quickly than those in which the driving-irrelevant feature changed - this shows that a feature that is more meaningful to the scene is attended to - when information is not attended to, the visual system is sometimes prone to inattentional blindness - inattentional blindness: failure to perceive an event when attention is diverted elsewhere ie. so engrossed in a hockey game, don’t notice best friend is in the row in front of you ie. the gorilla experiment: 50% of people failed to notice the gorilla, even though it happened in the centre of the action unusual nature of the event seems to make it more likely to be missed, because when they repeated the experiment, but with a woman carrying an umbrella, more people noticed her suggests the similarity of the unexpected event with the things we attend to determines inattentional blindness Brain Mechanisms of Selective Attention - possible explanation for selective attention: some components of the brain’s sensory system are temporarily sensitized, enhancing their ability to detect particular categories of stimuli ex. if a person is looking out for shapes, then we might be able to see increased activity in the parts of the visual cortex devoted to the analysis of shapes - selective attention toward different attributes of visual stimuli is accompanied by activation of the appropriate regions of the visual association cortex ie. paying attention to shape or paying attention to speed will activate two different regions of the visual association cortex - in a study of monkeys, certain neurons that received input from the appropriate part of the visual field began firing more rapidly, even before stimulus was presented these neurons seemed to be “primed” for detecting a stimulus in their visual field Consciousness and the Brain - brain damage can alter human consciousness ie. anterograde amnesia: damage to the hippocampus; can’t form new verbal memories, but can learn some kinds of tasks (unaware that they learned something new, but behaviour indicates that they have) brain damage doesn’t prevent all learning, but it prevents conscious awareness of what has been learned - human consciousness is related to speech, so its probably related to the brain mechanisms that control hypothesis: for awareness of some info, it must be transmitted to neural circuits in brain responsible for our communicative behaviour Isolation Aphasia - isolation aphasia: a language disturbance that includes an inability to comprehend speech or produce meaningful speech w/o affecting ability to repeat speech and learn new sequences of words; caused by brain damage that isolates the brain’s speech mechanisms from other parts of the brain speech mechanisms could receive auditory input, and control the muscles used for speech, but they receive no info from the other senses or from the neural circuits that contain memories about past experiences and the meanings of words Case Study - woman who had isolation aphasia: - case suggests: consciousness is not just activity of the brain’s speech mechanisms, it is activity prompted by info received from other parts of the brain concerning memories or current events Visual Agnosia: Lack of Awareness of Visual Perceptions - people may become unaware of only particular kinds of information ie. in blindsight, people can point to objects that they’re not aware of seeing - visual agnosia: inability of a person (who is not blind) to recognize the identity of an object visually; caused by damage to the visual association cortex ex. look at hammer, can’t recognize it by sight, but could identify it when he picked it up Case Study - man with visual agnosia: he had great trouble visually recognizing objects he often made hand movements related to the object he could not identify patient’s visual system was not normal, but it functioned much better than inferred from only his verbal behaviour (his perceptions were much more accurate than his words indicated) case supports: consciousness is synonymous with a person’s ability to talk about their perceptions or memories in this case, disruption in the normal interchange b/w the visual perceptual system and the verbal system prevented patient from being aware of his own visual perceptions; instead, it’s like his hands talked to him, telling him what he had just seen The Split-Brain Syndrome - epilepsy: storms of neural activity begin in one hemisphere and go to the other through the corpus callosum; both sides then go through wild firing and stimulate each other-> an epileptic seizure - split-brain operation: surgical procedure that severs the corpus callosum, abolishing the direct connections b/w the cortex of the 2 cerebral hemispheres (greatly reduces frequency of epileptic seizures) - normally, the 2 hemispheres exchange information through the corpus callosum, it makes sure that activities are coordinated each hemisphere receives sensory information from the other side of the body, and controls muscle movements on that side (*with one exception) - when the hemispheres are disconnected, they operate independently, they can no longer exchange information effects of these disconnections are not obvious to most people bc. only one hemisphere (left) controls speech right hemisphere of an epileptic person with a split brain can understand speech reasonably well, but is poor at reading/spelling Broca’s speech area is located in left hemisphere, thus right is incapable of producing speech bc. only left side of the brain can talk about what it is experiencing, a casual observer won’t detect the independent operations of the right side of a split brain at times, left side of the body will do weird thing
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