Chapter9.doc

Chapter 9: Consciousness Consciousness as a Social Phenomenon ● first position on consciousness is that it is not a natural phenomenon and that it is supernatural and miraculous not to be understood by human mind ● second position is tha consciousness is natural phenomenon but also that we cannot understand it for various reasons – exists because of nature of human brain  our brains cannot grasp concept  do not have methods to study it yet  poorly defined ● third position is that consciousness is produced by activity of brain and that we should be optimistic about our ability to understand it (Hebb) The Adaptive Significance of Consciousness ● consciousness is awareness of processes in brain, not processes themselves ● consciousness does not exist – humans have ability to be conscious ● most likley explanation for consciousness lies in its relation to deliberate, symbollic communicaion – our ability to communicate (words, signs, other symbollic meaning) provides us with self-awareness --> social phenomenon (like communication) Consciousness and the Ability to Communicate ● through communicating symbolically we can express our needs, thoughts, perceptions, memories, intentions, and feelings to other people ● require 2 general capacities:  must be able to translate private events (needs, thoughts, etc) into symbolic expressions ■ brain mechanisms we use to communicate with others must receive input from systems of brain involved in perceiving, thinking , remembering, etc  our symbols (words) must have effect on other person listening ■ once words are decoded in listener's brain they must affect listener's own thoughts, perceptions, memories and behaviour ● having both of these capabilities allows us to communicate with ourselves ● thinking in words involves subvocal ariculation – brain mechanisms that permit us to understand words and produce speech are same ones we use to think in words ● ability to communicate with ourselves symbolically gives rise to consciousness – conscious of private events we can talk about to others or ourselves: our needs, perceptions, intentions, memories, and feelings  people who are deaf sometimes think with their hands  people mouth words to themselves ● experiment by Cheesman and Merikle – presented people with word (primer) that was either congruent or incongruent with coloour of subsequent stimulus (target) and people were asked to name target; between primer and target on some trials there was random jumble of visual lines  found that incongruent primers produced Stroop-like interference even when jumble interfered with ability to consciously identify word  presented same experiment with many more congruent than incongruent primes so that by using primer people could predict what colour was about to come  when primer was consciously perceivable people used it to predict target but when it was not consciously perceived people failed to use it  consclusions: we become able to describe and thereby use psychological events tha are private to ourselves ● some animals are conscious – dogs can learn to communicate with owner by communicating symbolically ● underlying brain mechanisms, such as those of explicit memory system may be present in species closely related to us – behaviour of primates in mirror suggest they have concept of self-awareness ● computer could learn to communicate symbolically with itself and us Evaluating Scientific Issues: Does Conscious Thought Control Behaviour ● previously psychologists would not study consciousness because it was not observable behaviour – Descartes thought human actions were controlled by non- material mind (dualism); William James thought emotional awareness came after reaction ● recent evidence from cognitive psychology and neuropsychology provides way of thinking about issue of conscious control of behaviour – some evidence uses phenomenon of visual illusions  2 crayons – horizontal looks shorter (“top hat illusion” - because it is often demonstrated using judgments about crown vs brim of hat)  Ganel and Goodale – compared perceptual judgments of object shape with ability to pick up object and showed people wooden block on table and asked them whether block was wider or narrow and repeated with different blocks ■ easy to judge width if blocks are all same length but if length was different then task was difficult ■ grasping actions was not affected by variation in length ● perceptual awareness of objects may be based on different visual system than one we use for actions ● Ebbinghau illusion – circle surrounded by big circles looks smaller than circle surrounded by small circles but if you were to reach for them your behaviour would be unaffected by relative size  introspective experiences would tell us that they were diferent in size but behaviour would reflect otherwise ● thought and action go together but is correlation – could be third action of brain that causes action and thought ● Libet – asked people to make hand motion while watching rapidly moving clock hand and were to report where clock hand was at time they became aware of an intention to move  reports indicated that they experienced awareness of intention 3/10 of a second before motion  also measured “readiness potential” - electrical brain activity of motor cortex prior to movement ■ occured about 7/10 of a second before motion ● Haggard and Eimer – reasoned that if readiness potential was cause of movement then it should show covariation in time with awareness  asked participants to move right or left mand and to report when they were aware of intention to move  looked at occasions where report of awareness was late (closer in time to actual movement) to see if readiness potential was also late and found that it was not  also looked at lateralized readiness potential (measures activity specific to side where movement occurs) and found that it did covary with report of awareness ■ when awareness was late/early so was lateralized readiness potential ● lateralized readiness potential may reflect brain acitvity that leads to awareness about action – but is specific to one side of cody that moves, which presumably means that it must follow more general decision to make any movement; may be only part of sequence of brain activity leading up to conscious awareness ● Haggard, Clark, and Kalogeras – looked at awareness of voluntary and involuntary movement  induced muscle twitches (moved hand) by magnetic impulses delivered through surface of scalp  watched clock hand spin around dial and reported where hand was when they felt intention to move or involutnary movement produced by simulation  some trials were operant trials – tone came ¼ of a second after movement and person was asked to report time of tone  on operant trials – reported times of voluntary movement were late and reported times of following tone were early: opposite of involuntary trials where reported time of movement was ealry and reported time of tone was late  people's subjective experience of sequence was that, on voluntary tirals, movement and tone were close together and on involuntary trials perception was that they were further apart  brain must bind together experience of voluntary movement with its external consequences  binding perhaps helps us recognize those external events that are consequences of our behaviours Consciousness and Moral Reasoning ● Anderson – reported case of 2 individuals who suffered brain damage to prefrontal area of brain before they were 2 years old  had normal intellectual functioning but no moral or social reasoning ■ inability to recall social and moral knowledge ■ history of poor social and moral adjustment Selective Attention ● not conscious of all stimuli detected by our sense organs ● selective attention – process that controls our awareness of, and readiness to respond to, particular categories of stimuli or stimuli in a particular location ● sensory memory receives moreinformation than it can transfer into short-term memory ● Sperling – found that although people couldn't remember all letters he flashed, they could direct their attention to any of 3 lines and identify them with perfect accuracy ● process of selective attention determines which events we become conscious of ● attention may be controlled automatically (intense stimuli), instructions, or by demands of particular task we are performing ● attention to visual events in particular tends to act like spotlight that highlights events within some spatially contained area ● our attentional mechanisms serve to enhance our responsivness to certain stimuli and to tune out irrelevant information – determines what is stored in short term memory and long term memory ● storage of information in explicit memory dosen't require conscious attention ● Broadbent – brain mechanisms responsible for conscious processing of information have limited capacity so need some system to control flow of information Auditory Information ● Cherry – devised test of selective attention called dichotic listening  dichotic listening – task that requires person to listen to one of two different messages being presented simulataneously, one to each ear, through headphones  asked participants to shadow (continually repeat verbal material as soon as it is heard) message presented to one ear – ensured that they would pay attention to only that message  message that entered unattended ear appeared to be lost – participants recognized they had heard something but could not say what it was and didn't even notice if it was presented in foreign language ● suggest channel of sensory input can be turned off – perhaps neurons that detect sound from unattended ear are inhibited so they cannot respond to sound presented to that ear ● other evidence shows taht selective attention is not achieved by simply closing sensory channel – some information by its very nature can break through into consciousness (will remember hearing name, sexually explicit words) ● filtration must occur after sounds are identified as words ● McKay – showed information presented to unattended ear can influence verbal processing even when listener is not conscious of information  reported sentences related to what words that were presented to in unattended ear – sentences were not the same as onces actually heard; meaning was skewed in relation to what word was presented to unattended ear  participants did not recall hearing those words but obviously affected perception ● Sachs – shown people quickly forget particular words in sentences but remember meaning for much longer ● able to store information as it comes in ● Treisman – showed that people can follow message that is being shadowed even if it switches from one ear to another  even though unshadowed message cannot be remembered later, it produces some trace that can be retrieved if attention is directed to it soon after words are presented ● cocktail-party phenomenon – ability to sort out one voice from another and string together jumble of sounds into meaningful message ignoring rest Visual Information ● can successfully attend to location of information or to nature of information ● Sperling's studies on sensory memory were probably first to demonstrate that role of attention in selectively transferring visual information into verbal st memory ● Posner, Snyder, and Davidson – had people watch computer-controlled video display screen with small mark in centre of screen that served as fixation point for participants' gaze  showed warning stimulus near fixation point followed by target stimulus (letter displayed to left or right of fixation point) – warning stimulus consisted of arrow pointing to left or right or plus sign which served as cues to participants where to expect target and plus sign as neutral stimulus  pressed button when they detected letter  80% - arrow pointed accurately; 20% - arrow pointed away from location  response was faster when arrow corresponded correctly ● shows that selective attention can affect detection of visual stimuli – if visual stimuli appears where we expect it then we perceive it more quickly ● neural circuits that detect particualr kind of stimulus are some how sensitized so taht they can more easily detect stimulus and in some cases, mechanisms of selective attention sensitized neural circuits that detect visual stimuli in particular region ● if arrow is non-predictive but presented right before target, people are still faster at identifying stimulus if arrow pointes correclty to it – attention is still focused to where arrow pointed even if it is not right ● if arrow is much earlier than letter (100-300 milliseconds) then recognition is slower when letter appears at location of cue – Posner called it inhibition of return ● inhibition of return – reduced tendency to perceive target when target's presentation is consistent with noninformative cue; attentional spotlight sweeps momentarily over location of cue, swings back, and is then inhibited from returning immediately to same spot; usually is tested with respect to spatial location and is present when target is presented several hundred milliseconds after cue ● O'Donnell and Pratt – experiment simliar to inhibition of response; found that when cross appeared on same side of cue recognition was slower than when it appeared on other side; inhibition of response occured to two inside boxes when outside boxes were cues but not other way around ● inhibition of return may be closely lilnked to motor circuits in visual system ● second dimension of visual attention is anture of object being attended to ● two events can happen in close proximity but we can ignore one ● Neisser and Becklen – showed people videotape that presented situation similar to one confronted by person at cocktail party (contained two different actions on top of each other – basketball game and hand game)  people could only follow one scene at a time ● visual system is prone to inattentional blindness – failure to perceive an event when attention is diverted elsewhere ● Sioms and Chabris – participants watched basketball game and asked to count passes; women is guerilla suit walked in and nobody noticed but people did notice when game was interupted by woman with umbrell a ● Simons makes suggestion that while our visual experience is rich with information, our ability to represent it in memory may be limited ● when we focus our attention on part of external world, our consciousness relies on stability of rest of it ● change blindness – failure to detect change when vision is interrupted by a saccade or artificially produced obstruction ● factors that control our attention include: novelty, verbal instructions, and our own assesment of singificance of what we are perceiving Brain Mechanisms of Selective Attention ● possible explanation for selective attention is that some components of brain's sensory system are temporarily sensitized, which enhances their ability to detect particular categories of stimuli  eg. if person were watching shape we would see increased acitvity in portion of visual cortex devoted to analysis of shape ● Corbetta – had people look at computerized display containing 30 colured rectangles which could change in shape, colour, or speed of movement and ask them to pay attention to one attribute (same display every time)  used PET scanner to measure brain activity and found that paying attention to different attributes caused different appropriate regions of visual cortex to be activated ● Luckm, Chelazzi, Hillyard and Desimone – obtained similar results in study using monkeys  recorded activity of single neurons in visual association cortex  when cue indicated that monkey should be watching for stimulus to be presented in particular location, neurons that received input from that visual field fired more rapidly even before stimuli was presented – neurons were primed for detecting stimulus in their part of visual field Biology and Culture: Control of Consciousness ● expectations and customs of society substantially influence effects that drugs have on person's consciousness ● can alter, expand or escape own consciousness without use of drugs ● function that all methods of changing consciousness have in common is alteration of attention ● various exercises can be divided into those that withdraw attention from stimuli around us and those that increase attention to events that have become so commonplace that we no longer notice them – exercises called meditation Techniques for withdrawing attention: ● goal of most meditation exercises is to remove attention from all sensory stimuli – to think of nothing ● direct attention to specific object, spoken of imagined word or phrase, monotonous sound, or to repetitive movement – by doing this we learn to ignore other stimuli ● two primary goals: to reduce verbal control over non-verbal functioning of brain and to produce afterwards a rebound phenomenon - heightening of awareness and an increase in attention (conscious increasing exercises) Techniques for Increasing and Dishabituating Consciousness: ● habituation to most stimuli in our environment enables us to concentrate on stimuli that are important to survival ● techniques for reducing awareness help reduce habituation ● easiest way to reduce habituation and automatic functioning is to encounter novel stimuli, do things differently, do something dangerous or something that demands skill and coordination, or remove oneself from world temporarily – suppressed attention mechnisms rebound Consciousness and the Brain ● brain damage can alter human consciousness ● anterograde amnesia – damage to hippocampus  cannot form new verbal memories but can learn new kinds of tasks – unaware that they have learned something new even when behaviour indicates otherwise ● if consciousness is related to speech, then it is probably related to brain mechanisms that control comprehension and production of speech ● suggestes that for use to be aware of information, it must be transmitted to neural circuits in brain responsible for our communicative behaviour Isolation Aphasia: A Case of Global Unawareness ● Geschwind, Quandfasel and Segarra – described case of woman who had suffered sever brain damage from inhaling CO from faulty water heater  damage spared primary auditory cortex, speech areas of brain and connections between two  damage destroyed large parts of visual association cortex and isolated speech mechnisms from other parts of brain  isolation aphasia – language disturbance that includes inability to comprehend speech or to produce meaningful speech without affecting ability to repeat speech and to learn new sequences of words; caused by brain damage that isolates brain's speech mechanisms from other parts of brain  woman's speech mechanisms could receive auditory input and could control muscles used for speech, but received no information from other senses or from neural circuits that contain memories concerning past experiences and meaning of words  woman made few movements except with her eyes which were able to follow moving objects – gave no evidence of recognizing objects or people  didn't spontaneously say anything, answer questions, or give signs that she understood what other people said to her  could repeat words that were spoken to her and she could finish poems she knew and learned new poems and songs ● case suggests that consciousness is not simply activity of brain's speech mechanisms – it is activity prompted by information received from other parts of brain concerning memories or events presently occuring in environment Visual Agnosia: Lack of Awareness of Visual Perceptions ● visual agnosia – inability of person who is not blind to recognize identity of an object visually; caused by brain damage to visual association cortex  can have difficulty visually recognizing objects or pictures of objects but can made hand movements that appear to be related to oject and by paying attention to those movements can identify object  visual system worked well enough to initiate appropriate non-verbal behaviour, though not appropriate words  patient lost ability to read but was taught to use finger spelling to read – couldn't say what letter was but could make particular hand movement when he saw it; learned ASL finger-spelling alphabet and could read slowly by making hand movements for each letter and feeling words his hands spelled out ● supports conclusion that consciousness is synonymous with person's ability toi talk about his or her perceptions and memories – disruption of normal interchange between visual perceptual system and verbal system prevented patient from being directly aware of his own visual perceptions The Split-Brain Syndrome ● split-brain operation – surgical procedure that severs corpus callosum, thus abolishing direct connections between cortex of two cerebral hemispheres ● Sperry and Gazzaniga – studied split-brain patients ● normally cerebral cortexes of left and right brain exchange informati