Lecture 5: Consciousness PDF

Lecture 5 : Consciousness Type Status Not started Consciousness & Intelligence and Unconscious Processes The Mind-Body Problem: The nature of the mind-body or mind-brain connection was a philosophical question of importance...

Lecture 5 : Consciousness Type Status Not started Consciousness & Intelligence and Unconscious Processes The Mind-Body Problem: The nature of the mind-body or mind-brain connection was a philosophical question of importance in the early days of cognitive science Monism : There is only one kind of substance in the universe Idealism: Everything – including the material world – is actually mind Materialism: Everything that exists – including mind – is physical In some fundamental sense, the mind just is the brain, so that everything that happens in the mind is happening in the brain. Aristotle: The brain is like a lump of clay; the different thoughts the mind can take on when it undergoes different patterns of activity are like the shapes the clay can assume. Most cognitive scientists hold this view (materialism) Dualism: The mind and brain are two separate and distinct things. Belief in the existence of both mental (e.g., “soul”) and physical substances > Few cognitive scientists are dualists Functionalism, on the other hand, holds that we need to emphasize function, to understand how things produce their effects What makes something a thought, desire, pain (or any other type of mental state) is solely its function, or the role it plays, in the cognitive system of which it is a part. More specifically, the identity of a mental state is said to be determined by its causal relations to sensory stimulations, other mental states, and behavior Functionalism (understanding how things produce their effects) results in a high-level understanding that can be implemented in multiple different ways. That is, those functions no longer have to be tied to a specific type of structure or material, e.g., neurons or the brain Functionalism is actually officially neutral between materialism and dualism, but it tends to be associated today with materialism, and specifically, the view that each type of mental state is identical with a particular type of neural state, due to an increased emphasis on neuroscience in the last 25 years Intelligence & Physical Symbol System (PSS) Hypothesis Lecture 5 : Consciousness 1  One of central ideas of philosophy of artificial intelligence. Proposed in 1975 by computer scientists Herbert Simon and Allen Newell. Holds that all intelligent behavior essentially involves transforming physical symbols according to rules. A physical symbol system is basically an abstract characterization of a digital computer Implications: Anything capable of intelligent action is a physical symbol system. Since humans are capable of intelligent action, the human mind must be a physical symbol system. Since a physical symbol system is sufficient for intelligence, machines can be constructed that are intelligent Thinking = manipulation of symbolic representation structures In humans, symbol systems are instantiated in the brain The same symbol systems can also be instantiated in a computer John Searle’s Chinese Room Argument Tries to show that the physical symbol system hypothesis is completely mistaken. Describes a situation in which symbols are manipulated to produce exactly the right outputs, but where there seems to be no genuine understanding and no genuine intelligence ]Searle also thinks that the Chinese room argument reveals a fundamental problem with the so-called Turing Test Proposed by Alan Turing in 1950 as a criterion for whether a machine is displaying real intelligence. Turing Test (TT) = If an observer is communicating with a machine and cannot tell the difference between it and a human being, then that would show that the computer was genuinely intelligent Rebuttal to the Chinese room argument: The Chinese room does not understand Chinese, but only because it is disembodied. In order to build a machine that could do all this, we would need to embed the Chinese room in a robot, providing it with some analog of sensory organs, vocal apparatus, and limbs. Then the system could be said to understand Chinese and behave intelligently Searle’s response to robot reply: The basic problem still remains: simply manipulating symbols cannot create meaning.There must be more to genuine thinking than simply manipulating symbols according to rules What Is Consciousness? Consciousness is generally defined in psychology as “awareness of our environment and our perceptions, images, and feelings.”Some philosophers, like John Searle, have argued that consciousness is an emergent property of a physical brain. That is, it may not be fully explained by an understanding of its component parts. Neural Correlates of Consciousness Neuroscientists generally hold that consciousness results from the coordinated activity of a population of neurons (all about neurointegration). Currently, there are two main theories: 💡 1. Global Neuronal Workspace Theory 2. Integrated Information Theory (Guilio Tononi) Global Neuronal Workspace Theory of Consciousness Global workspace theory: Explains how information is made accessible for high-level cognition, action, and speech. When we are conscious of something, many different parts of our brain have access to that information. When we act unconsciously, that information is localized to the specific sensory motor system involved Lecture 5 : Consciousness 2  Ex: When you type fast, you do so with little conscious awareness, so that, if asked how you do it, you would not know ➜Information is localized in brain circuits linking your eyes to rapid finger movements Global workspace theory maintains that consciousness forms when specialized programs or modules access a shared repository of information or “blackboard”. Data written onto this blackboard becomes available to a host of subsidiary processes, such as working memory, language, the planning module, etc. 💡☞ Consciousness emerges when incoming sensory information, inscribed onto the blackboard, is broadcast globally to multiple cognitive systems Global neuronal workspace (GNW) theory Evolved from global workspace theory The network of neurons that broadcasts messages widely (as described in previous slide) is hypothesized to be located in the frontal and parietal lobes Theory proposes a distributed network of high-level processors, most likely in the prefrontal, parieto- temporal, and cingulate cortices Once that information is broadcast on the network and is globally available, it becomes conscious global workspace (remember the filter model of attention?) Various types of nonconscious processing are associated with deficits in these areas, including: Hypnosis, Repression and dissociative identity disorder, Non-lucid (as opposed to lucid) dreaming, and Unilateral visual neglect Hypnosis is associated with Decreased activity in the dorsal anterior cingulate (selective attention). So absorbed that one is not thinking about anything else Reduced connections between the dorsolateral prefrontal cortex (motor actions) and the default mode network (awareness of one’s actions), which includes the medial prefrontal and the posterior cingulate cortex Repressed memories: Recovered memories of child abuse Dissociative identity disorder (multiple personality) Condition in which two or more identities or personalities alternate in control of a person’s behavior. One personality can be diabetic, nearsighted, or allergic to a substance and the other not. The two personalities can have different brain waves, vital signs and hormonal levels. Some personalities are aware of the other personalities Lecture 5 : Consciousness 3  💡 Research indicates that in repression/dissociation, the prefrontal cortex (executive control) disengages processing in the hippocampus (memory) Participants asked to memorize word pairs, e.g., ordeal-roach or steam- train Respond condition: Participants were shown cue word and asked to recall the matched word Suppress condition: Participants were shown cue word and asked to actively suppress the matched word ➜Word suppression was associated with activation of prefrontal cortex to disengage processing in hippocampus. Suppressing matched word reduced later recall of word 💡 Brain is actually more active when avoiding recalling a memory than during recall itself Lucid dreaming: Neuroimaging data is scant but preliminary results suggest that prefrontal and parietal regions are also involved in lucid dreaming Currently, there is only one fMRI study contrasting lucid and non- lucid REM sleep and it is a case study. Interestingly though, the results of this study converge with MRI studies that have evaluated individual differences in lucid dreaming frequency Compared to non-lucid REM sleep, lucid REM sleep is associated with increased activity in Prefrontal cortex: (metacognition and self-reflection) Parietal cortex and the precuneus (self-referential processing, episodic memory, and experience of agency) Occipital and inferior temporal regions (visual processing) Lucid dreams are oftentimes associated with and the (self-referential increased visual vividness and clarity of the dream scene Visual neglect syndrome or unilateral spatial neglect: Tendency to ignore – or to be unaware of – information on one half of visual field, usually the left side. Typically occurs after damage (e.g., stroke) to right hemisphere, particularly damage to the parietal and frontal lobes 💡 However, other research suggests that it is primarily regions in the “posterior hot zone” – not the prefrontal – that generate the sights, sounds, and other sensations of life as we experience it Lecture 5 : Consciousness 4  Prior to removing a brain tumor or locus of a patient’s epileptic seizures, neurosurgeons map functions of nearby cortical tissue by directly stimulating it with electrodes Stimulating the posterior hot zone triggers a variety of distinct sensations and feelings Stimulating the frontal cortex by and large elicits no direct conscious experience Similar effects have been found after removal of cortical tissue Removal of large sections of frontal cortex (e.g., prefrontal lobotomy) does not significantly affect conscious experience, though patient may develop problems with emotional control, motor deficits, or uncontrollable repetition of specific actions or words However, removal of even small regions of the posterior cortex can lead to loss of an entire class of conscious content – patients may be unable to recognize faces or to see motion, color, or space 💡 ★One possible reason for the discrepancy in research findings is that the part of the cerebral cortex that is primarily associated with consciousness depends on the type of consciousness in question In particular, some philosophers have distinguished between two types of consciousness: 1. Access consciousness (or A-consciousness): pertains to accessibility of information, i.e., conscious vs. nonconscious information processing Prefrontal and parietal cortical areas may play important roles in this Related to the “easy problem” of consciousness: explaining in computational or neural terms how an organism accesses and deploys information 2. Phenomenal consciousness (or P-consciousness): pertains to how and why we experience the world as we do Posterior hot zone may play critical role in this This is what David Chalmers has called the “hard problem” of consciousness Hard Problem of Consciousness Why and how is it that sentient organisms have qualia or phenomenal experiences? Lecture 5 : Consciousness 5  Why and how is it that some internal states are felt states (e.g., heat or pain, rather than unfelt states (e.g., a thermostat or a toaster)? ✤According to Frank Jackson’s Knowledge Argument, a colorblind scientist who knew every (third-person) scientific act about color perception would still lack first-person knowledge of what it is like to see color – and would probably be quite shocked if he saw a red rose for the first time 💡 The Global Neuronal Workspace Theory of consciousness lends insight to access consciousness. 💡 Integrated Information Theory, address the problem of phenomenal consciousness One thing though that most researchers agree on is that the seat of consciousness is not located in the cerebellum, though this part of the brain contains Four times as many neurons as the cortex.Half the total number of neurons in the whole brain People who lack a cerebellum (either from birth or as a result of brain injury) are still capable of conscious perception, leading a “normal” life without any loss of awareness ➜Suggests that sheer number of neurons is not a decisive factor in the creation of conscious experience But why? One reason might be that the cerebellum’s processing mostly happens locally with minimal interactions between neurons The cerebellum is almost exclusively a feed-forward circuit with no complex feedback loops that reverberate with electrical activity passing back and forth It’s functionally divided into hundreds of independent computational modules with distinct, nonoverlapping inputs and output, controlling movements of different motor or cognitive systems 💡 This idea that exchange and integration of neural signals is the basis of phenomenal consciousness is one of the main ideas of integrated information theory Integrated Information Theory In the early 2000s, Guilio Tononi pioneered a technique called zap and zip to probe whether someone is conscious or not 💡 Scalp of patient was “zapped” with an intense pulse of magnetic energy using TMS (transcranial magnetic stimulation) This induced a brief electric current in the neurons underneath, which would reverberate across the cortex, exciting and inhibiting other neurons A network of EEG sensors recorded those electrical signals, and as they unfolded over time, yielded a movie The data from the movie was compressed using an algorithm commonly used to “zip” computer files Zipping yielded an estimate of the complexity of the brain’s response Data from zap and zip: Lecture 5 : Consciousness 6  Research findings from zap and zip: Volunteers who were awake had a “perturbational complexity index” significantly higher than when deeply asleep or anesthetized Method was subsequently able to correctly determine whether patients were conscious or in a vegetative state Measures of the brain’s responses to the TMS also seem to predict the consciousness of patients in a non- communicative and vegetative state – a finding with potentially profound clinical applications ➜This suggests that the more information that is shared and processed between many different components of the brain in response to a single experience, the higher the level of consciousness 💡☞ This is the main idea of integrated information theory (IIT): Consciousness arises from neural integration and complexity. “the more complex and more integrated the activity” Tononi argues that the basic architecture of the computers we have today – made from networks of transistors – precludes the necessary level of information integration that is necessary for consciousness. Even if they can be programmed to behave like a human, they would never have our rich internal life. He emphasizes this is not just a question of computational power or the kind of software that is used Controversies in Cognitive Science Unconscious Processes Some prominent psychologists today maintain that 100 years of research has provided no clear evidence for the existence of the “unconscious,” but that claim seems to be exaggerated. By one estimate, our five senses take in 11,000,000 bits of information per second, of which we consciously process about 40 Some specific evidence for the existence of the unconscious… Consciousness and thought suppression —> White bear/red Volkswagon study Group 1: Participants were told to try not to think about white bears Group 2: Participants were told to try not to think about white bears but if they did, to replace the thought with the image of a red Volkswagon Which group was more successful? ➜ Group 2 💡☞ It’s very difficult (if not impossible!) to suppress a maladaptive thought; it’s much easier to replace the thought with a more desirable one Lecture 5 : Consciousness 7  Unconscious behaviors Split brain: a condition in which the two hemispheres of the brain are isolated by severing the connecting fibers (mainly those of the corpus callosum) between them After operation, patients often notice that left hand seems to have a “mind of its own” 💡☞ Suggests that consciousness involves operations of verbal mechanism located in left cerebral hemisphere This tendency to only be conscious of and identify with the left-brain self is also evidenced in alien hand syndrome, also known as Dr. Strangelove syndrome Alien hand syndrome: person experiences their limbs acting seemingly on their own and lacking conscious control over the actions Condition most commonly affects the left hand At times, the alien hand may even try to harm the individual There are a variety of possible causes, including stroke, tumor, trauma, or a neurodegenerative disorder The disorder may involve damage to: Corpus callosum, Medial frontal lobe: control of movements, Parietal lobe: sensory feedback regarding movements Unconscious perception Subliminal perception and priming. Rope tying study Participants are asked to tie together two strings that are hanging from the ceiling. The strings are separated so that they can’t reach one of them while holding the other. A table and pliers are made available. At some point, the researcher walks into the room and accidentally sets one of the strings swinging.Invariably, within a few minutes, the participant would figure out the solution to the problem... ➜When interviewed afterwards though, they said that the idea “just came to them” Subconscious processing under anesthesia: Surgery patients in double-blind study wore earphones during their operations, listening to Soothing background music and Positive suggestions about the safety and success of the procedure. Results: Compared to controls, experimental group: Woke up feeling significantly less pain (25% on average). Required less pain medication post- surgery (70 required no opiates at all, compared with 39 in the control group) Repressed memories (unconscious process) Recovered memories of child abuse Dissociative identity disorder (multiple personality) Anosognosia: “unawareness of illness” Stroke patients with this disorder may deny that his arm is paralyzed Lecture 5 : Consciousness 8  Unconscious conditioning in advertising Men shown picture of car with sexy woman standing in front judged car to be more appealing, better designed, more expensive, faster, and less safe than control group of men However, 22 out of 23 participants denied their rating had been influenced by the presence of the model 💡 Unconscious processing and sexual attraction: we are often influenced by factors of which we are entirely unaware Suspension bridge study Males were interviewed by attractive female supposedly as part of research project, either Just after crossing a narrow, wobbly footbridge 230 feet above rapids OR 10 minutes after crossing the bridge They were given the researcher’s telephone number in case they had questions later ➜Those in first condition were much more likely to call to ask for a date afterwards 💡☞ Participants had no idea their attraction was influenced by the situation Lecture 5 : Consciousness 9