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Midterm

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Department
Psychology
Course
PSYC 213
Professor
Jelena Ristic
Semester
Winter

Description
History, Definitions, and Introduction to Cognitive Psychology 12/6/2013 1:20:00 PM Cognitive psychology studies both low level and high level processes  Low level: chemical reactions, neuronal reactions  High level: cognitive processes, complex process that yields with many lower level processes combined Input (senses)  Brain  Output Cognitive psychology: (Urlic Neisser’s definition) “The term "cognition" refers to all processes by which the sensory input is transformed, reduced, elaborated, stored, recovered, and used. It is concerned with these processes even when they operate in the absence of relevant stimulation, as in images and hallucinations... Given such a sweeping definition, it is apparent that cognition is involved in everything a human being might possibly do; that every[2] psychological phenomenon is a cognitive phenomenon. But although cognitive psychology is concerned with all human activity rather than some fraction of it, the concern is from a particular point of view. Other viewpoints are equally legitimate and necessary. Dynamic psychology, which begins with motives rather than with sensory input, is a case in point. Instead of asking how a man's actions and experiences result from what he saw, remembered, or believed, the dynamic psychologist asks how they follow from the subject's goals, needs, or instincts.” Folk psychology: a set of assumptions and theories based on everyday behaviors of others and ourselves Oxford dictionary: the action or faculty of knowing  Action of knowing  Study of processes: the ways in which we become acquainted with things  Awareness, comprehension, intelligence, intuition, personal acquaintance, recognition, sill and understanding Historical Perspectives Dialectics: progression of scientific knowledge  Thesis: statement  Antithesis: opposing argument  Synthesis: combining thesis and antithesis to create a new thesis  Historical root of cognitive psychology  Philosophy: seeks to understand the general nature of the world using primary introspection  Physiology: study of the structure and function of the living matter using primarily experimental approach Dialectics: Rationalism vs Empiricism 18 Century Synthesis: Immanuel Kant  Both rationalism and empiricism are important Rationalism: arriving at knowledge based on previous knowledge, what we already know to be right  Plato  Development of theories Empiricism: knowledge based on observation, experimentation and testing  Aristotle  Development of the scientific method 1. Structuralism vs. functionalism  Structuralism: understand the configuration of the elements of the mind by studying the components of percepts. Using introspection. o Wilhelm Wundt  Shape  Color  Geometrics  Functionalismpragmatism (William James) o How do the elements work together  Synthesis: Associationism o How events become associated with one another to result in learning  Ebbinghaus: studied memory  Thorndike: the key to making associations is the satisfaction or a reward  Law or effect: a stimulus will produce a response 2. Behaviorism vs cognitive psychology Behaviorism: the focus of psychology should be the study between the stimulus and the response  Stimulus-response relationship  Shift from human to animal research  Classical conditioning (Pavlov)  Watson – there is no internal mental states B.F Skinner – All humans behavior can be modified by stimulus-reaction relationships. Brain is passive. Behavior is contingent on the schedule of the rewards/punishments  Bandura: vicarious learning. Learning results from rewards and punishments to others  Gestalt psychology: experience of percepts  Karl Lashely: the brain is dynamic and active as oppose to passive o Skinner response: language is S-R o Chomsky: language is creative. Children produce sentences without rewards/punishments  Technological advancements: mind as a computer metaphor  Cognitive psychology o Accepts existence of internal mental states o Accepts the scientific method of inquiry (rejects introspection as the main method)  Late 1960s – cognitive revolution. Emergence of cognitive psychology  Understanding and representing mental operations o Vocabulary and jargon (ex: mental representations, mental transformations, concepts, schemas)  Information processing o Important for understanding and measuring mental operations o Mental operations are embedded in time o Basis for experimental measurements 3 stages of communication 1. sender 2. communication channel 3. receiver (decoding) o * Response Time (R-T) is intimately related to information processing Information theory Information processing  Shannon and Weaver  All forms of communication could be broken down into a sequence of events with at least three major stages: sender, a communication channel and a receiver o Sender: encodes the message, puts what wants to be communicated into an appropriate signal o Signal transmitter via communication channel (a wire, air etc.) o Receiver: receives the signal and decodes to get the message  Information reduces uncertainty in the mind of he receiver  Amount of information provided by a message is proportional to the probability of that message occurring  Information processing theory is the idea that the information provided by a particular message is not determined solely by the signal itself, but rather by the whole array of possible messages of which this particular signal is just one  Amount of information a message conveys is an increasing function of the number of possible messages from which that particular message could have been selected Information theory: the information provided by a particular event is inversely related to its probability of occurrence Bit: short for ‘binary digit’ – and event that occurs in a situation with two equally likely outcomes provides one ‘bit’ of information  Every time he number of equally likely alternatives doubles, then the number of bits goes up by one Models for information processing E.g., Broadbent’s Filter model Filter model: based on the idea that information processing is restriced by channel capacity Channel capacity: the maximum amount of information that can be transmitted by an information processing device  When more than one signal or message occurs at the same time, they entered parallel to the sensory buffer, which extracts such simple stimulus characteristics such as color, voice, spatial location  Filter operates by selecting messages that share some common physical characteristics, and passing these messages along to the limited capacity system, which is responsible for the analysis of the ‘higher-order’ stimulus attributes, such as form and meaning  Other messages are held, in parallel, in the sensory buffer where they are subject to decay with the passage of time  Filter represents selective attention, and acts as the one ot determine which channel is recalled first  One the messages decay, harder to recall them over time E.g., Waugh and Norman’s model Introspection: the act of observing one’s own thoughts and feelings, as they seem to oneself Primary memory: consists of what we are aware of in the ‘immediately present moment’, often termed ‘immediate memory’ or ‘short term memory’  Makes it possible to immediately and accurately recall our most recent experiences Secondary memory: the knowledge of a former state of mind after it has been absent from awareness for some period of time, also called ‘long term memory’ Gibson Ecological approach: a form of psychological inquiry that reflects conditions in the real world Affordances: the potential functions or uses of stimuli in the real world Information pick up: the process whereby we perceive information directly E.g., Neissers Model Schema: our expectations concerning what we are likely to find as we explore the world  Automatically impose this expectation  As a consequence we perceive  As we continue to explore, our expectations may change and come to the true state of affairs Perceptual cycle: the process whereby our schema not only guides exploration of the world, but also is shaped by what it finds there  Allows us to become increasingly sophisticated in out dealings with the environment Cognitive psychology: a new research approach hat links the real world observations with lab- based investigations Metacognition: the knowledge people have about the way certain cognitive processes, work, how accurately you can assess you own cognitive processes New approaches:  Cognitive neuroscience  Cognitive ethology  Modeling behavior as a dynamic system  Modeling behavior based on brain function Chapter 1: Introduction Summary This chapter introduces the field of cognition. Cognition is presented as the study of processes, or as the act of knowing. Aspects that are related to the subject of information processing include: awareness, comprehension, intelligence, intuition, personal acquaintance, recognition, skill, and understanding. According to information processing, uncertainty can be decreased with the acquisition of information. Information theory maintains that the less likely a signal is, the more information it contains (conversely, when a signal is more probable, the amount of information it contains is reduced). Furthermore, when a signal is less likely to occur, people seem to respond more slowly to it. On top of the nervous system dealing with time limitations, it has also been demonstrated that it shows signs of capacity limitations (amount of information handled at a given time). Capacity limitations do not signify that simultaneous tasks are impossible to complete, rather that impairment of simultaneous tasks depends on the information load. In order to complete certain overloaded tasks, people select only the pertinent information and disregard the rest. Broadbent’s filter model is a classic theory of information processing. It states that the brain acts as a limited capacity channel in that it only allows certain information through, which is then filtered according to basic physical characteristics and then by form and meaning. Messages or stimuli that did not get through are held in parallel in the sensory buffer, where they will decay with time. Broadbent went further in stating that switching attention between two different tasks decreases performance. Another classic model of information processing was that of Waugh and Norman. This model maintained that primary memories (immediate memories) have a tendency to be forgotten unless they are rehearsed (versus secondary memories). The Brown-Peterson task supported this idea. Unlike previous models that were primarily focused on the processes that people use to deal with information, Gibson promoted an ecological approach to cognition, based on information pick-up, which focused on the stimuli that exist in everyday life scenarios as opposed to those that exist in laboratories. For Gibson, learning is about absorbing the tremendous amount of information available to us in the environment. Neisser’s perceptual cycle, on the other hand, describes learning as an active cognitive process of exploration and modification of schemas. Cognitive ethology is an intermediate approach between standard, laboratory-based, experimental approaches and the ecological approach. Despite its many theories and its impressive abilities to explain some human behaviours, it is important to remember that cognitive psychology is still a young and developing field of study. Review Questions 1. Explain the primary function of information. When does a response yield the most information? 2. According to Broadbent’s filter model, at which point in the model would the identity of a stimulus be processed? 3. What is the difference between Gibbon’s notion of information pick-up and Neisser’s notion of perceptual cycle? 4. You hear the mail being dropped in your letter box; you pick it up and notice that, once again, some of the mail is not for you. On further inspection you notice that the postman confused the street number 2406 with yours: 2460. Can you name some obvious aspects of information processing you have just performed? 5. Identify one of the cognitive concepts and explain how it relates to cognition? 6. Explain how Shannon and Weaver suggest that communication can be broken down. 7. What concept is central to all theories of information processing? 8. Experimental evidence demonstrates that people have a slower response to less likely signals. How does information processing theory interpret these results? 9. What does the Brown-Peterson task demonstrate? 10. Describe the criticism cognitive ethology launches at standard experimental research approach. What does cognitive ethology propose to do differently? Answers 1. Information reduces uncertainty and its value increases as the probability of a response occurrence decreases. (p.8) 2. Identity/meaning of a stimulus would be processed in the limited capacity channel after filter selection. (p.13) 3. For Gibbon, we absorb the richness of information offered to us in the environment whereas for Neisser it is our expectations that guide our exploration of the environment and through this exploration we modify our schemas to enhance their accuracy. (p.16) 4. Perceiving/attending, remembering, comprehending, and problem solving are all part of this scenario. (p.6) 5. Example: Recognition is to ‘know again’ by categorizing information as something we have experienced before. (See p. 6 and Table 1.1 for more alternatives.) 6. Shannon and Weaver proposed that all forms of communication could be broken down into a sequence of events with at least three stages: sender, communication channel, and receiver. The sender encodes the message (ex: words), then it is transmitted through the communication channel (ex: printed page), when it is received by the receiver who decodes the message (ex: translates). 7. The central idea behind information processing is that of information theory: the information provided by a particular message is not determined by the signal alone, but by the whole array of possible messages of which that particular message could have been selected. The less likely a signal is, the more information it conveys. (p. 8) 8. Information theory states that the less likely a signal is, the more information it contains. Furthermore the slower a response is, the longer it takes to process it. If more information takes longer to process, this suggests that the nervous system has a limited capacity for the amount of information it can handle within a fixed period of time, whether visual or auditory. (p. 11) 9. It shows that recall declines as interference increases. Also, that without rehearsal, repetition, or any further processing, very little is retained. (p. 15) 10. Cognitive ethology criticizes the standard research approach as being based on the faulty assumption that cognitive processes always work the exact same way in any given situation. Cognitive ethology proposes that we instead observe naturally occurring behaviour, move it to a lab setting and gradually simplify the relevant factors. Lab findings should then be tested to see if they predict and explain behaviour in its natural setting. (p. 19) Cognitive Neuroscience 1/10/2012 10:07:00 AM Definition: a field that seeks to uncover the links between cognitions and the brain  Fueled by the rise of neuroimaging techniques that allows for imaging of LIVE brain function Modules: the sections of the brain each responsible for particular cognitive operations Phrenology: study of the shape and size, and protrusions of the cranium in an attempt to discover the relation between parts of the brain and various mental activities and abilities Localization of function: the attempt to discover correspondences between specific cognitive functions and specific parts of the brain, based on the assumption that there is a strict one-to- one correspondence between specific functions and specific parts of the brain Histology: microscopic analysis of the tissue structure Law of mass action: learning and memory depend on the total mass of the brain tissue remaining rather than the properties of individual cells Law of equipotentiality: even though some areas of the cortex may be specialized for certain tasks, within limits any part of the brain can do the job of any other part Key Principles:  Cognitions arise from the brain  Based on interdisciplinary or convergent methodologies Mind-Body Mind-body dialectics: how the mind and the body interact  17 century Franz Joseph Gall o Phrenology: specific cognitive fucntins can be localized in the brain Specifying the mind-body relationship: 1. Interactionalism  Descartes: mind and body are separate but they interact (pineal gland and the ‘seat of the soul’)  Roger Sperry: split brain studies o Split brain: consciousness is an emergent property  Interhemispheric transfer: communication between the brain’s hemispheres is enabled in large by part of the corpus callosum  Split brain: a condition creating by severing the corpus callosum  Emergent properties: ‘mind’ comes about as a resul of the brain processes, but is not itself a component of the brain. This means that the mind is not reducible to or predictable from other features of the brain  Emergent causation: ‘mind’ emerges from the brain, it then has the power to influence lower level processes  Supervenient: mental state may influence neuronal events while being influenced by them 2. Epiphenomenalism  Mind is a byproduct of the brain  Mental states are caused by physical states  Mental states do not influence physical states 3. Parallelism  Fechner: mind and brain are two aspects of the same reality – one-to-one correspondence  For all events in the mind there will be a corresponding event in the brain 4. Isomorphism  Cognitions and the bran share the same pattern rather than point-to-point correspondence  Consciousness doesn’t consist of simply one event after another but tends to be organized into a coherent whole o Gestalt  External stimulus is constant but the internal subjective experience varies  When the cube changes orientation there must be a corresponding change in the structure of the underlying brain process  Cortical representations of the signal become tired and only weakly capable of supporting electrical fields, and so another part of the cortex begins to represent the figure Methods of Cognitive Neuroscience 1. Neuroanatomy (postmortem)  Study of the parts of the nervous system o Gross neuroanatomy (general structures)  individual neuroanatomy (individual neurons) 2. Neurophysiology (inVivo-Invasive)  Measuring and manipulating neuronal activity  Types of electrodes: recording and stimulating o Macroelectrodes-region/population of cells o Microelectrodes-single cell o Ex: Perrett: face cells in superior temporal sulcus (STS) 3. Lesion studies and neurology  How removal or alterations of a particular brain region affects behavior/cognition a) Animal irreversible  Stereotactic surgery-atlas guided  Aspiration lesion-vacuum  Neurochemical lesions-selectively destroy neurotransmitters  Electrolytic-electrical current o Sham lesions = control group Animal reversible – allows the relationship between different brain regions to be specified  Chemical-transient disruption  Cooling of neural tissue o Control group is the tested group b) Human irreversible (Neuropsychology)  Brian injury resulting from:  localization of one or more fucntions o Vascular disorders (bleeding, hypoxia, aneurysms) o Tumors (mass of tissue pushing on structures) o Degenerative disorders (Alzheimer’s, Parkinson’s) o Head Trauma (open/closed, TBI) Human reversible  TMS o Single vs double dissociations 4. Functional neuroimaging of the brain o Modern tools that allow us to study live healthy human brain in action a) Computerized Axial Tomography (CAT)  Structural image of tissue  No functional data b) Positron Emission Tomography (PET): participants injected with radioactive substance that mingles with the blood and circulates to the brain. A scanner is then used to detect flow of blood to particular areas of he brain. When active, oxygen is used up at faster rate than when inactive, increase blood flow to that area in order to replenish it with oxygen  Structural (provided by CT or MRI)  Primarily metabolic measure of glucose reuptake  Increase brain activity = increase glucose metabolism  Radioactive tracer that binds with glucose molecules is picked up by the scanner  Tracer reuptake takes time, so temporal resolution is bad fMRI: a non-radioactive magnetic procedure for detecting flow of oxygenated blood to various parts of the brain  Atoms of the brain become aligned at the magnetic fields, constructs an image of cortical activity c) Magnetic Resonance Imaging (MRI)  Functional magnetic resonance imaging (fMRI)  Metabolic changes in oxygenated/deoxygenated blood  BOLD: Blood Oxygenation Level Dependant  Excellent social resolution < 1s  Bad temporal resolution >1s d) Electroencephalography (EEG)  Brains electrical activity at scalp  Excellent temporal resolution – real time  Bad special resolution ~ 10mm  ERP (Event Related Potentials) o EEG activity time locked to a specific event o Red hot o e) Magnetoencephalography (MEG)  Brains electrical activity, but picks up magnetic fields  Excellent temporal resolution-real time  Somewhat better special resolution f) Transcranial Magnetic Stimulation (TMS)  Reversible human lesions  Transient disruption of human brain activity by the application of a focal magnetic field o Caveats in data interpretation  Correlational method  Links between brain activity and behavior ERP: event related potential: electrical signals recorded from the brain that occur after the onset of a stimulus  Need additional or supplemental techniques to get whole picture of the brain process and it is only suggestive Connectionism: the theory that cognitive processes are regulated by complex systems of a large number of interconnected elements  Neural networks: a system of connections between elements that models connections between neurons and the nervous system Assumption 1 Hebb rule: a connection between two neurons takes place only if both neurons are firing approximately at the same time Assumption 2 Parallel processing: many neural connections can be active at the same time Serial processing: only one neural activity can take place at any one given time 5. Behavioral methods  Measure participants behavior o Chronometric measures (RT, Accuracy) o Eye tracking measures (movement and position of eye) o Subjective reports (paper and pencil tests) o Relating brain activity and behavior Assumptions  Neural activity underlies cognitive processes  Cognitive function can be localized in the brain  Mental representations are stable over time  The system (the brain) is stable over time  Behavioral tasks tap directly into the working of the specialized brain areas Chapter 2: Cognitive Neuroscience Summary This chapter introduces the theoretical approaches and practical methodologies common to the field of cognitive neuroscience. Cognitive neuroscience is an interdisciplinary field dedicated to the study of brain mechanisms and of the human mental functions that are intimately associated with these brain mechanisms. Originally theorists such as Gall and Spurzheim attempted to map specific mental functions to specific locations of the brain. This localization of function approach has its roots in phrenology—the ‘science’ of divining personality traits from the physical features of the skull. Later theorists such as Franz and his students introduced a new approach—rooted in the laws of mass action and equipotentiality— which maintained that mental processes result from of the brain as a whole and not from individual parts. Due to its equal consideration of both mental functions and brain functions, cognitive neuroscience does not limit itself to studying the human brain as a mere organ, and thus often finds itself at the cross-roads of the seemingly unresolvable philosophical debate over how mind and brain relate. Descartes’ interactionism theory maintains that the mind and brain are separate, although they interact with and each can influence the other. Another view is Huxley’s concept of epiphenomenalism, which postulated that the mind is merely a by-product of the brain, and thus only the brain has any causal influence. Fechner, on the other hand, supported the idea of parallelism, whereby the mind and the brain are simply two aspects of a single reality. Finally, isomorphism, which is related to Gestalt psychology, extends the claims of parallelism further in claiming that internal representations and the underlying brain processes are inherently organized into patterns, and that these patterns in the mind and brain are similar in all their structural traits. There are several methods that researchers used and still use today in order to conduct their inquiries or support their theories. A popular, although limited way to explore human processes and behaviours is the use of animal models. A second way to examine brain functions is to conduct behavioural studies in humans. Researchers can either study healthy participants or subjects with brain injuries. Although no single case of brain injury provides definitive results, studying large numbers of individuals can lead to important breakthroughs in the understanding of brain functioning (e.g., Broca’s and Wernicke’s areas and aphasias). Similarly, surgical intervention can also be insightful (Sperry’s split brain studies). Another research method consists of placing electrodes on the scalp and measuring the electrical signals emitted in response to a stimulus (event-related potential). Position emission tomography (PET) can also be used to determine which areas of the brain are active during select tasks. However, because it requires subjects to be exposed to radioactive substances, PET has recently been replaced with functional magnetic resonance imagery (fMRI). fMRI measures changes in blood oxygen levels with the aid of a large magnetic field and has been used to make assumptions on cortical activity. None of these methods tells the whole story of what the brain is doing and when it is doing it, but they do provide a useful aid in understanding human brain functioning. In addition to the methods that measure brain activity, other approaches, such as connectionism, aim to model mental functions based on brain-like neural networks. Review Questions 1. What distinguishes information theories based on parallel processing from theories based on serial processing? 2. What are the main differences between the interactionist perspective and the epiphenomenalist perspective? 3. Briefly define the term ‘event-related potential’. What can it be used for? 4. Briefly explain connectionism and how it differs from the more traditional information- processing approaches. 5. Briefly explain what fMRI measures and describe when it is a more appropriate technique than ERP. 6. Explain what is meant by the law of mass action and the law of equipotentiality. How do these perspectives differ from a strong localization of function perspective? 7. Explain the Hebb rule and how it is relevant to connectionism. 8. Isomorphism and parallelism are two very similar concepts, but what characteristics differentiate one from the other? 9. The law of mass action, and the law of equipotentiality are two constructs that have been put forth to discuss brain functioning. Briefly define both laws. 10. Define phrenology. To what extent is the practice related to the idea of localization of function? Answers 1. Parallel processing implies the occurrence of simultaneous activity across multiple neural connections, whereas serial processing implies the occurrence of a single neural connection operating at a time. In the latter model, one process must be completed before the next process begins. (p. 40) 2. The interactionist perspective implies that the ‘mind’ and ‘brain’ are separate entities which have the capacity to influence each other and therefore both can exert causal control over each other. In contrast, the epiphenomenalist perspective implies that the mind is a mere ‘by-product’ of brain activity, and as such has no causal influence over brain activity or behaviour. (pp. 28–29) 3. By strategically positioning electrodes on the scalp, electrical activity from the brain can be recorded and translated into graphs. When this is repeated over many trials for the same cognitive task, average ‘waveform’ patterns emerge in response to specific stimuli. These waveforms are called event-related potentials. They differ for different types of tasks. Interpreting their underlying cognitive processes is a challenging endeavour. Although ERPs can provide very high temporal resolution (on the order of a fraction of a second) they offer only limited spatial resolution (can only localize activity to large regions of the cortex). (pp. 35–36) 4. Connectionism is an information-processing approach which models cognitive processes based on networks of connections among elementary units (called neurons). The strength of the connections among the neurons is dynamic, and the connectionist network ‘learns’ by modifying the pattern of connection strengths so that the correct output (response) is achieved for any given input (stimulus). The connectionist approach differs from traditional information-processing approaches in that it attempts to model cognitive processes as they might actually be implemented by the networks of neurons in the brain. 5. fMRI directly measures the local blood-oxygen content in the brain, which is an indirect measure of local brain activity. It provides far greater spatial resolution than ERP, so fMRI would be the more appropriate technique when activity needs to be localized to specific brain structures. (p. 38) 6. The law of mass action states that a cognitive function depends on a total mass of brain tissue, and the law of equipotentiality states that to a certain extent brain regions are unspecialized and functionally interchangeable. These two laws differ greatly from the perspective of strong localization of function, which asserts that specific regions of the brain perform specific, specialized functions. (p. 27) 7. The Hebb rule states that when neuron ‘A’ repeatedly excites neuron ‘B’ and causes it to fire regularly and persistently, then the connection between neurons ‘A’ and ‘B’ will be strengthened. Alternatively put, ‘neurons that fire together, wire together’. The Hebb rule provides a way for connections between neurons in a connectionist neural network to be modified and strengthened. (p. 39–40) 8. Parallelism views the mind and brain as two distinct aspects of a single reality. For every mental event experienced by an individual, there is a corresponding event that occurs in the brain. The emphasis is that mental events are reflected in brain events, and vice versa. Isomorphism implies a similar concept, except that it emphasizes the organization of brain events and mental events, as wholes. Perceptual information for the same external/physical stimulus can vary, giving rise to differing brain events that process each ‘version’ of the external stimulus and result in different mental experiences of the stimulus. (p. 29) 9. The law of mass action states that learning and memory are the net results of neural functioning observed in masses of tissue. The law of equipotentiality states that while certain regions of the brain may be somewhat specialized in performing specific tasks, essentially brain tissue may perform any function and thus one are of the brain may compensate for losses in another area. (p. 27) 10. Phrenology was a nineteenth-century practice endorsed by Gall and Spurzheim that embraced the idea of localization of function to the extreme. Localization of function conveys the notion that brain regions can be divided up into discrete locations that are responsible for specific types of cognitive processing. Phrenology aimed to ‘map’ these regions of the brain by transcribing them off of the bumps located on a person’s skull. Whilst the concept of localization of function has found some merit in psychology, the idea that there is any correlation between bumps on a skull and cognitive traits has long since been abandoned. (p. 26–27 Perception 1/10/2012 10:07:00 AM Temporal Lobe Damage  Familiarity memory problems and NOT recency memory problems  Frontal Lobe Damage  Recency memory problems and NOT familiarity memory problems  Anatomy of the visual system  Subcortical and cortical systems  Topographic representation  Cortical magnification  Image is decomposed and composed back 1/10/2012 10:07:00 AM Seeing is not passive, it is constructive Constructive: quick and dirty estimate of the world  Uses shortcuts/assumptions o e.g., World is lit from above  World is stable (color/size constancy)  We do not see in rich detail  The brain sees  We don’t see in detail  Detail only in foveal vision  Attention limits severely what we see  The world is lit from above Theories of Vision How do scientists explain visual processes? Bottom-up vs. Top-down accounts  Bottom-up: building percepts from basic features  Ecological optics (J.J. Gibson)--passive  Pattern recognition accounts 1. Template matching Template: a model against which a stimulus is compared to determine whether it belongs to a particular category o Template pattern is stored in memory o The percept is compared to stored representation Prototype: a model that possesses all the typical characteristics of its class Template matching theory: comparing a stimulus with templates, when they match the stimulus is recognized as belonging to that category How are similar patterns matched?  Hinzman: multiple trace memory model  Primary memory—immediate perceptions  Secondary memory—stored perceptions  Traces are activated for every percept Multiple trace memory model: traces of each individual experience are recorded in memory. No matter how often a particular kind of event is experienced, a memory trace of the event is recorded each time Probe: secondary memory can be activated by means of a probe from primary memory Echo: when a probe goes out from primary to secondary memory, memory traces are activated to the extent that they are similar to the probe  Many memory traces are similar in the current experience  Properties of individual memory traces will tend to be lost, and only a general impression of what they all have in common will remain  **Distortions but not the prototype-memory traces of distorted patterns produce an echo, which contains distortions that are in common, prototype is recognized even though never seen it before 2. Feature detection: Perceptions are built from individual features  Selfridge-Pandemonium Feature: A component, part, or particular characteristic of a stimulus. Feature detection theory: A model of perception based on the hypothesis that we detect patterns on the basis of their individual features. Pandemonium model (Selfridge): A model of pattern recognition consisting of three levels: data, cognitive demons, and a decision demon. Cognitive demon: A little elf-like element of the pandemonium model of pattern recognition whose activity is linked to a specific letter.  A cognitive demon listens to the overall pattern of activity (yelling) among the feature demons to determine if its own letter is present. If so, it will start to yell. Decision demon: A little elf-like element of the pandemonium model of pattern recognition that determines the ultimate response (which letter is recognized).  A decision demon listens to the overall pattern of activity (yelling) among the cognitive demons to determine reach a final decision as to what letter is being represented. Contrast energy: The degree of contrast between letters in a word and the background they appear on leading to the relative ease with which a stimulus can be discriminated from the background against which it is displayed  Required for a participant to identify a word was highly related to word length  More letters, greater contrast energy required  More letters must detect per unit of time  High contrast energy words, signal represented by each letter is strong enough to enable detection even for such a brief presentation  Contrast energy low, identifying a large number of letters in a short period of time is too difficult, and the process of word recognition grinds to a halt Squelching: The tendency of the nervous system to inhibit the processing of unclear features.  Visual system tends not to guess but to rigorously detect features  Achieves reliability at the expense of efficiency  Vast number of features detectors, each of which can raise a false alarm, mistaking nose for signal  Blocks the intrusion of countless false features that would besiege us if weak features were not suppressed 3. Recognition by components (RBC): A model of perception based on subdividing objects into a basic set of geometric shapes. Geons: According to the Recognition by Components theory of object recognition, the basic geometric shapes that comprise objects  Once object are reduced to Geons, the theory states that the resulting Geons are compared with existing Geon configurations stored in memory. When a reasonable match is made between input and memory, you recognize the object  People were good at recognizing objects represented by only 2 or 3 Geons, with accuracy being around 80% at the worst  For a given object, recognition ability was progressively better when more detail was included with the addition of more Geons.  More complex objects were recognized more efficiently than less complex ones  COUNTER INTUITIONwhat complexity and detail provide is more Geons, and more Geons head to better recognition  When objects are degraded such that Geons cannot be extracted, then the object recognition will fail Recoverability: the degree to which Geons can be made out in degraded image of an object 4. Recognition by views  Pattern/template matching  Recognize objects by most dominant view  Templates contain most usual views  People recognize objects faster when they are presented in the most typical view Context and Knowledge Bottom-up (data-driven) processing: When perception (or other cognitive processes) results from the combination of individual pieces of sensory information.  Based on prior knowledge, goals and expectations to the act of perceiving  Observer factors can influence perception Top-down (user-driven) processing: When perception (or other cognitive processes) is driven by expectations and prior knowledge.  Interprets the blocky image with a grid as a picture of a young person with something like a window screen between the observer and the person  Visual system constructs a clearer experience than one that is provided alone  Context effects: The influence that the situation plays on the perception of a stimulus. Moon illusion: The tendency for the moon to appear larger when on the horizon than when high in the sky  Apparent distance theory: An explanation for the moon illusion, which posits that the moon on the horizon appears larger because ‘distance’ cues lead the observer to perceive it as being nearer than the zenith moon.  Angle-of-regard theory: the theory developed to explain the moon illusion, which states that the zenith moon appears smaller than the horizon moon because a person has to raise her or his eyes or head to view it Information in the environment is important BUT so is how humans actively construct their perceptions Recognize configurations (interaction between perception and memory) Pattern recognition  an ability to recognize an event as an instance of a particular category. Letters in context Jumbled word effect: The ability to raed wdors in steentnces dsepite hvinag mexid-up ltteers in teh mlidde of smoe of the wrods. The ability to recognize words in sentences despite having mixed up letters in the middle of some of the words.  Expectation of the words in a sentence help determine the words actually are  Letter swapped in middle, no effect  Letter swapped at the beginning or end, drastic effect Word superiority effect: In cases of ambiguity, it is easier to identify a letter (e.g., ‘D’) if it appears in a word (e.g., ‘WORD’) than by itself. Parallel distributed processing (PDP): Another name for connectionist models that allow parallel processing; a model of perception that proposes that different features are processed at the same time by different units connected together in a network.  Simple processing elements called unites are sending excitatory and inhibitory signals to other units  Specifies the microstructure of cognition  Working out detailed models on a highly specific level of the way in which processes like pattern recognition work  A unit is active by being present in the letter being perceived  Excitatory and inhibitory connections between units determine what you end up seeing Colors in context  Color visiontop down processing has an impact on what you see  Perception of color is influenced by the perceptual context in which an object appears Empirical theory of color vision: The proposal that color perception involves not only the processing of wavelengths of light but also the influence of prior experiences about how different lighting conditions affect the appearance of the colors of objects. Cross modal context McGurk effect: the auditory experience of a syllable ‘da’ when seeing a mouth silently saying ‘ga’ while at the same time hearing a voice saying ‘ba’  Perception of sound is altered by visual cues made by the mouths movements of the visible person  Context does not come from the same modality but from a different one The Grand Illusion Change blindness: The failure of people often to notice changes to an object or scene.  We feel that we perceive all of the information in our visual dield with high resolution BUT we fail to detect large changes across scenes which suggests that this feeling may be an illusion Grand illusion of perception: The illusion that our visual system provides us with a faithful and accurate portrayal of our environment.  Likely to process one or two objects in detail at a time  Result of a considerable amount of top down interpretation of a very fragmentary visual information Feature Integration theory Feature integration theory (fit): The proposal that attention must focus on a set of features before they can be combined into a whole. Preattentive processes: The process of feature extraction that operates outside of awareness. Feature binding: the combining of visual features by attention to form whole objects  To perceive an object as a whole there must be feature binding at a specific location  Accomplished by attentive processing Attentive processing: The combination of features into a whole object through the process of attention.  Roughly only one object is bound and experienced as a whole in a given moment Pop out: A salient feature that jumps out of an image. Constraints of visual system High-fidelity percept is not possible because 1. Visual information is degraded as it moves through the visual organs to the brain 2. Information from all area of viewed space is not equally represented in the brainvisual acuity is not going to be the same across whole field of vision **retina at the back of the eye, and the visual cortex of the brain  decrease in visual processing for peripheral information Blind spot: A region in the eye where the optic nerve leaves the retina and which does not contain any photoreceptors.  Visual light not being processed Perceptual completion (filling-in): The experience that something is present in part of a visual scene when actually it is absent from that spot, but is present in the surrounding region. Perceiving whole objects Gestalt Psychology: A branch of psychology that posits a whole possesses more than just the sum of its parts  Resulting percept is not simply a straightforward function of the elements in the visual field o Bi-stable figures: Images from which two separate precepts can be formed.  Whole that is perceived is an entity in its own right and is different from just the sum of its partsexact same features or elements can be recombined to form very different perceptual objects Holistic: focusing on the whole configuration of an object Atomistic: focusing on the features or components of objects Organizational principles: The rules that explain the ways in which people are able to perceive whole objects or events from individual parts. Group: The way in which individual parts are combined to form a whole Organizational Principles Principle of experience: gestalt organization that states that elemnts are grouped based on the prior experience and knowledge of the observer  Least endorsed idea Figure/ground organization: Perceptual organization of a scene such that one element becomes the foreground (figure) and the other element(s) become(s) the background (ground). Denotivity: the degree to which an object is meaningful and familiar to an individual  High  meaning and familiarity  Low  unrecognizable Principle of proximity: things that are near ne another are grouped together Principle of closure: Things that form closed shapes are grouped together. Principle of good continuation: Things that form continuous lines are grouped together. Principle of similarity: Things that are similar are grouped together. Principle of common fate: Things that are moving in the same direction are grouped together. Limitations of Gestalt Perception Ceteris paribus: A Latin term that means ‘when all is equal’.  Principle function by this term which means they determine how we group items when everything other than the principle in question is kept constant  In real world things are always interacting and this principle did not specify the way we will or will not group objects under these conditions Gestalt error: the assumption that whole objects should always dominate over the elements of an image  Processing of local elements sometimes overrides the whole pattern and determines what we perceive  The percept and interpretation of an image change depending on the distance of the observer from the image Dissociations of Perception Apperceptive agnosia: A form of visual agnosia marked by a difficulty matching or categorizing objects.  Can copy well  Unable to judge orientation of objects  Able to orient hand normally when reaching or grasping Optic Ataxia: a neural deficit in which the patient can identify objects but is unale to accurately interact with them manually  Cannot grasp and reach Prosopagnosia: impairment in the ability to recognize faces despite intact recognition of other objects  Cannot consciously recognize faces  May be able to unconsciously recognize faces  Unconscious recognition of familiar objects is accompanied by a small increase in the conductance of skin caused by mild perspiration o Skin conductance response: the small increase of conductivity of the surface of the skin when an individual is aroused by seeing a familiar object or person Capgras syndrome: A condition marked by the belief that significant others have been replaced by imposters, doubles, robots, or aliens.  Consciously recognizes faces without any problem but feel like imposters have replaced close relatives  Can recognize familiar faces but do not show the skin conductance responses that normal and prosopagnosics do when covertly recognizing the faces Chapter 3: Perception Summary This chapter introduces the field of perception: the process by which sensory information is processed to create our conscious experiences of the environment and to guide our actions. Because it is our most dominant sense and because it dominates the field of perceptual research, visual perception is the focal point of this chapter’s treatment of perceptual processes. Perceptual processes are often divided into two major, complementary types of processing: bottom-up (data-driven) processing and top-down (user-driven) processing. Bottom-up processing refers to the contribution of the physical features of the stimulus to our perceptual experience. A great deal of bottom-up theories arose from pattern recognition, which itself was based on two theories: template matching (multiple-trace memory model, Posner experiments) and feature detection (pandemonium model). Biederman offered yet another theory, known as the recognition-by-components theory (RBC), which explains how we rapidly recognize objects based on their constituent, basic, 3-dimensional elements (geons). Treisman developed yet another theory (feature integration theory), which maintains that objects are first processed preattentively, then attentively. Top-down processing, on the other hand, relates to perception that is influenced by goals, expectation,ns and prior knowledge. The ‘word superiority effect’ is a prototypical example of this type of processing. Connectionist models (parallel distributed processing) also support effects of context on perception, as do phenomena such as the ‘jumbled word effect’, change blindness (Levin et al. experiments), or filling-in (perceptual completion). Top-down processing is not only limited to semantic effects, it also impacts colour vision. According to the empirical theory of colour vision, we use prior knowledge of how objects look under certain lighting, as well as bottom-up processing in order to perceive colour. Aside from bottom-up and top-down hypotheses, Gestalt psychology was also an influential perspective on the topic of perception processing. The Gestalt approach emphasizes that ‘the whole that is perceived is greater than the sum of its parts’ and illustrated this idea with the use of perceptually bi-stable images. Gestalt psychology’s most influential principle maintained that people have a tendency to group items so as to form the simplest arrangements (Prägnanz). They formulated further principles of perceptual grouping based on similarity, proximity, closure, good continuation, and common fate. One Gestalt psychologist in particular (Rubin), developed a figure/ground organization theory. These principles of perceptual grouping developed by Gestalt psychology are not firm rules of how perceptions are organized and are thought to be most accurate when everything else is equal (ceteris paribus). Putting all these perspectives together forms a view on perception that is referred to as the constructivist approach. This approach emphasizes that perception is a process of reconstructing the environment as an internal representation from all of its perceptual elements. A very different view of perception was developed by J.J. Gibson, who focused not on reconstructing the environment, but on directly perceiving its properties—without intervening processing. Gibson contributed a great deal to the idea of perception with concepts such as ambient optic arrays (AOAs), texture gradients, and affordance. Finally, another route to understanding perception is to be found in the study of deficits in visual perception, as in cases where patients suffer from visual agnosia or Capgras Syndrome. When interpreted in light of the various theoretical perspectives previously mentioned, deficits such as these can be quite insightful. Review Questions 1. What is meant by the Höffding function and how does it contribute to the process of recognition? 2. How does the template-matching theory envision object recognition, and what is the major weakness of this theory? 3. Accoring to Hintzman (1986), how is secondary memory activated through primary memory? 4. Describe Biederman’s (1986) theory of Recognition by Components (RBC). 5. What is the word superiority effect and how does it differ from bottom-up processing accounts of letter recognition? 6. What is the notion of the ‘grand illusion of perception’ and how does ‘change blindness’ lend credence to this notion? 7. What is the main difference between Gestalt psychology and the views of the Structuralists? 8. How is Gibson’s ecological approach different from the constructivist approach to perception? 9. What are apperceptive agnosia and associative agnosia? 10. How do patients who suffer from prosopagnosia differ from those who suffer from Capgras Syndrome? Answers 1. The Höffding function describes how an emerging percept makes contact with a prior memory trace, resulting in the recognition of the percept as the object previously stored in memory. For this contact to occur the object must have been previously perceived and a trace of that experience must have been left in memory (memory trace). To recognize the object again, the new emerging percept must make contact with the previous memory trace. (p. 50) 2. According to template-matching theory, we store ‘templates’ of objects (or letters) in our memory. The process of recognition then involves matching the object we see with our stored representations to find a ‘match’. The major weakness of this theory is that it is difficult to account for how recognition can occur for objects that are only similar (and not identical) to a given template. 3. Primary memory activates a probe, which is then sent to secondary memory. Within secondary memory this probe activates memory traces which are similar to the probe. These memory traces are then relayed back to the primary memory in the form of an echo. (p. 51) 4. RBC is a theory which assumes that any perceivable object can be broken down into fundamental building blocks, for which the term ‘geons’ (geometric ions) was coined. It further states that only a few geons from any given object need to be discernible for that object to be correctly identified. (p. 53) 5. The word superiority effect is the observation that people more easily recognize a letter when it appears in the meaningful context of a word rather than when it appears alone or in a nonsense word. It differs from bottom-up processing accounts of letter recognition in that it emphasizes the effects of context, knowledge, and expectations, rather than the individual visual features of a letter, on letter recognition. (p. 61) 6. The notion of the ‘grand illusion of perception’ suggests that our internal representation of the external world is not as rich in detail as we experience it. It claims that we actually have a very fragmented and detail-poor representation and that top-down processing seems to fill-in a considerable amount of missing detail. Change blindness lends credence to this notion in that if our internal representation of the world were rich in detail, then we would be expected to notice when our conversation partner changes identity in mid-conversation. (p. 63–65) 7. Gestalt psychology advocates that the whole is greater than the sum of its parts; that is, that we actively organize parts into more meaningful wholes. Gestalters used bi-stable images to illustrate that different perceptions may be organized from the same set of elements. Structuralists believed that the whole is equal to the sum of its parts and thus did not allow for organization to play a role in perception. (p. 67) 8. The constructivist approach views perception as a process of constructing an internal representation (or picture) of the world from basic perceptual elements. Gibson’s approach, on the other hand, viewed perception as a process of directly obtaining information offered by the external world without any intermediary processes such as organizing and constructing. (p. 71) 9. Apperceptive agnosia is the inability to recognize an object due to an inability to create a coherent perception of an object or even simple geometric shapes despite adequate visual fields, acuity, and colour vision. Associative agnosia refers to the inability to recognize an object despite the ability to correctly perceive it as indicated by the ability to reproduce a drawing or match a picture of the object. (pp. 77–78) 10. Patients with prosopagnosia suffer from a conscious impairment of face recognition, while retaining an ability to recognize familiar faces below the threshold of awareness (as measured by SCR). Patients with Capgras Syndrome show the opposite facial recognition capabilities. These patients are able to consciously distinguish familiar faces from unfamiliar ones, but they appear to lack the non-conscious recognition. It is thought that the lack of non-conscious recognition leads to an emotional distance when looking at familiar faces, leading to the assumption that loved ones are imposters. (p. 79) Attention 1/10/2012 10:07:00 AM What is Vision For?  Neuropsychological studies  Visual agnosia: Prosopagnosia  Inability to recognize familiar faces o Acquired (injury to the brain) o Congenital (genetic?) States of Arousal How to define attention? William James (1890)  “Everyone knows what attention is. It is the taking possession of the mind, in clear and vivid form, of one out what seem several simultaneously possible objects or trains of thought…It implies withdrawal from some things in order to deal effectively with others, and is a condition which has a real opposite in the confused, dazed, scatterbrained state which…is called distraction.” Harold Pashler (1998)  “No one knows what attention is, and…there may not even be an “it” there to be known about (although of course there might be).” Metaphors of attention  Posner-Spotlight o Zoom lens o Center that’s illuminated well, and periphery that’s blurry o Things in center are caught by attention, and fades away with space  Eriksen-Zoomlens  LaBerge-Gradient o The resources are allocated to the center and as the space widens, less and less attention resources are allocated Properties of attention 1. Attention is selective  Only a few things are attended Dichotic listening: Participants are exposed to two verbal messages presented simultaneously, and are required to answer questions posed in only one of the messages Selective attention: attending to relevant information and ignoring irrelevant information. Cocktail party phenomenon: the capacity for attending to one conversation in a crowded room in which many other conversations are going on. Shadowing task: exposing the subject to two messages simultaneously while repeating one of them. Selective looking: a visual analogue of dichotic listening in which one is exposed to two sequences of events simultaneously, but attends only to one Early selection: the hypothesis that attention prevents early perceptual processing of distractors Late selection: the hypothesis that both relevant and irrelevant stimuli are perceived, so that the person must actively ignore the irrelevant stimuli in order to focus on the relevant ones. Filter: a stage of information processing that admits some messages but blocks others At what stage in processing does attention act? Broadbent Early Filter Late Filter Accounts E.g, Stroop Effect Stroop task: a list of color names, each of which is printed in a color other than its name  Compares performance in an incongruent condition  With control conditions  Reliably found that the incongruent condition takes more time than oes a control condition  If a process has been overlearned than there may be a tendency to execute that process whther or not we with to do so  If you are presented with a list of words, and you know how to read, it is hard not to read them Controlled versus automatic processes: processes to which we must pay attention in order to execute them properly versus processes that run themselves without the necessity of our paying attention to them.  Automatic process is autonomic, runs by itself without the necessity of our paying attention to it o Bottom up o Stimulus driven o Involuntary  Controlled: must pay attention if we are to execute them properly o Top down o Goal-directed o Voluntary Dorsolateral prefrontal cortex (dlpfc): an area of the brain that may exert a top-down bias that favors the selection of task-relevant information.  Exerting control when task-irrelevant information can effectively compete with task- relevant information for priority in processing Anterior cingulate cortex (ACC): an area of the brain that may detect conflicting response tendencies of the sort that the Stroop task elicits.  Communicating with other equally essential components within its network and having multiple functions depending on the content and origin of the signals from other components in the attentional network Attention Capture and Inattentional Blindness Attention capture: the power of some stimuli on some occasions to grab our attention in spite of the fact that we did not intend to pay attention to them  Ecologically useful as it enables attention to be drawn to new objects in the field because they may well represent either an important threat to be avoided or an important opportunity to be sought out  We are tuned to pick up on useful information even when our attention is directed elsewhere Inattentional blindness: our failure to recall seeing events to which we were not attending Flanker task: an attentional task that involves a visual target presented with distracters located adjacently. The distracters are called ‘flankers’  Faces will attract attention to a greater extent than will other classes of stimuli  Congruent condition-search for bill Clintons name while his picture is being shown  Incongruent condition-searching for Michael Jackson’s name while bill Clintons face was shown o Take longer than congruent, showing that faces were not ignored bt interfered with reaction time o Size of distractor effect was the same at all levels of list length o Effect of list length and a congruence effect, with incongruent trials generally take longer o Congruence effect was reduced and eventually disappeared as th list got longer o Task difficult increases  faces are still distractors o We attend to faces involuntarily even when our goal is to ignore them Domain-specific modules: the hypothesis that parts of the brain may be specialized for particular tasks, such as recognizing faces  Person’s own name has the power to capture that person’s attention  Primary determinany of selective attention and therefore of the content of perceptual consciousness  We see what interests us, what we are looking for and what we are expecting Perceptual cycleexpectancies guiding our exploration of the environment, ut the environment is capable of influencing our experiences of it  If attentional capture were always conditional on an intention, organisms would perceive only what they intended to see,, othr events would rarely be recognized, and threats would be frequently overlooked 2. Attention has limited capacity  Difficult to attend to two things at once o E.g., Divided Attention  Read and Copy Dictated Words  Additive Factors Logic (Donders, Sternberg) Capacity model: the hypothesis that attention is like a power supply that can only support a limited amount of attentional activity Structural limits: the hypothesis that attentional tasks interfere with one another to the extent that they share similar activities  Problem if you are trying to do two highly verbal tasks at the same time, imagining a sentence may require you to say it to yourself, and categorizing the words yous ay yes and no. Saying two things at once is not easy  Interference more likely when coming from same processing source Central bottleneck: the hypothesis that there is only one path through which information relevant to only one task at a time can pass  Central processor can only handle one task at a time 3 stages: a. Identifying stimulus b. Attentional bottleneck or central processor in which the appropriate response is selected c. Execution of the response **Able to achieve levels of performance under dual task conditions that were similar to those obtained under single task conditions **No proof of central bottlenecks that cannot be overcome without pratcie the ability to perform simultaneously without interference may require that the stimulus and response phases of each process be from different modalities Divided attention: the ability to attend to more than one thing at a time Task Switching Attentional set: temporary, top-down organizations that facilitate some responses, while inhibiting others, in order to achieve the person’s goals Switch cost: the indication that performance declines immediately upon switching tasks  Switching back feels like you have to restart  Due to time required to reset the cognitive system so that the behaviors appropriate to the current task are engaged once again and behaviors appropriate to the previous task are
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