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PSYC 310 1st Edition Lecture 5Outline of Last Lecture I. Types of Perception & DefinitionsII. Direct Perception TheoriesIII. Helmholtz’s Theory of Unconscious Inference (~1860)IV. Perceptual OrganizationOutline of Current Lecture I. Heuristics & AlgorithmsII. Neurons & the EnvironmentIII. Perception & ActionIV. Mirror NeuronsV. Signal Detection TheoryCurrent LectureI. Heuristics & Algorithmsa. Heuristic: “rule of thumb” (not concrete)i. Provides best-guess solution to a problemii. Fastiii. Often correctb. Algorithm: procedure guaranteed to solve a problemi. Slowii. Definite ResultThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.c. These Concepts apply to Perception as well as higher-order thoughtd. Other Perceptual Heuristicsi. Light from above heuristic1. Light comes from above2. Is usually the case in the environment3. We perceive shadows as specific information about depth and distanceii. Occlusion Heuristic1. When object is partially covered by a smaller occluding object,the larger one is seen as continuing behind the smaller occluderII. Neurons & the Environmenta. Physical &Semantic regularities in our environmentb. Neurons become tuned to respond best to what we commonly experiencec. Possible Explanations:i. Natural Selection1. Oblique Effect?ii. Experience-dependent plasticity1. Greeblesa. Like faces, greebles are unique but share common featuresb. Before training, greebles produced only very weak activation in fusiform face area (FFA)c. After training, greebles activated FFA almost as much as the faces didIII. Perception & Actiona. Two “streams” for visual perceptionb. What stream: Identifying an objecti. Inferior/Ventral temporal lobec. Where stream: identifying the object’s locationi. Posterior & Dorsal parietal lobed. Using Dissociation Logici. If you are trying to understand a complex system, you can logically deduce conclusions from “malfunctions”ii. Damage to different areas of the brain cause very different deficits1. We can conclude that a specific area is necessary for a specific functioniii. Brain Ablation method allows scientists to damage specific areas of otherwise normal brains (usually in monkeys or cats)1. Controlled damage allows for clear conclusions to be drawniv. Single Dissociation1. One function is lost, another remainsa. Ex: Monkey A has damage to temporal lobe. This monkey is no longer able to identify objects (what) but can still identify locations (where)2. Therefore, what and where rely on different mechanisms, although they may not operate totally independent of one anotherv. Double Dissociation1. Requires two individuals with different damage and opposite deficitsa. Ex: Monkey A with temporal lobe damage has intact “where” but impaired “what”; Monkey B with parietal lobe damage has intact “what” but impaired “where”2. Therefore, what and where streams must have different mechanisms AND operate independently of one anotherIV. Mirror Neuronsa. Neurons that respond the same way when actually performing an act and when observing someone perform that actb. Located in the premotor cortexc. One function of the mirror neurons might be to help understand another person’s actions and react appropriately to themd. Another proposed function is to help with imitationV. Signal Detection Theorya. Detection means classifying stimuli based on the presence/absence of some characteristici. Made difficult by natural variability in stimulib. The target characteristic is the signal, and the variability is noisec. SDT is a way of thinking about & analyzing these situationsd. Applies to perception, recognition memory, jury decisions, medical diagnoses, employee hiring, and many moree. Two Theoretical Distributionsi. Stimuli containing the signalii. Stimuli not containing the signalf. Each stimulus is scored on a theoretical “decision variable”i. Similarity to prototypical signalii. Amount of evidenceg. Challenge is identifying which distribution a given stimulus comes fromi. Some non-signals resemble the signalh. Subject is assumed to pick a criterion value on the decision variablei. Calls anything above the criterion a signali. Analysis:i. Hit Rate = hits/(hits + misses)ii. False alarm rate = Fas/(Fas +CRs)iii. Discriminability of the Distributions (d’)1. Distance between the distribution means d’ = z(Hit Rate) – z(FA Rate)iv. Bias of the criterion (c)1. C = -.5[z(Hit Rate) + z(FA Rate)]v. See if any variable affect these


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