UB PSY 341 - Psy341 lecture 3 (5 pages)

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Psy341 lecture 3



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Psy341 lecture 3

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Pages:
5
School:
University at Buffalo-SUNY
Course:
Psy 341 - Cognitive Psychology
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PSY341 Chapter 3 Perception Sensation o Absorbing raw energy ex light waves sound waves through our sensory organs Transduction o Conversion of this energy to neural signals Attention o Concentration of mental energy to process incoming information Perception o Recognizing selecting organizing and interpreting these signals Not an exact copy of the world Partially based on our past experience and expectations From Sensation to Representation Energy contains information about the world usually incomplete full of noise and distorted Sensory receptor transduces energy into a neural response o Equal playing field what matters is which nerves are excited o Stimulation of a specific nerve provides codes for that one sense Sensory nerve transmits the coded activity to the central nervous system Thalamus processes and relays the neural response o For all senses but olfaction which projects to the olfactory bulb Relayed to specialized areas of the cortex Bottom Up Processing Feature Matching Theories Recognize objects on the basis of a small number of characteristics features o Detect specific elements and assemble them into more complex forms o Brain cells that respond to specific features such as lines and angles are referred to as feature detectors Physiological Evidence For Features Hubel Wiesel 1979 Simple cells detect bars or edges of particular orientation in particular location Complex cells detect bars or edges of particular orientation motion direction Feature Searches Simple features seem to pop out o Fast processing o But sometimes need to engage in serial search for simple features o Occurs when distractors share simple feature as target Serial search o If feature doesn t pop out must rely on serial search Combined features don t pop out o Don t have conjoined feature detectors o Requires serial search Processing speed depends on number of distractors More distractors longer processing o Hierarchical processing Feature Analysis Bottom up processing Perception may start with the senses Incoming raw data Energy registering on receptors Top down processing Perception may start with the brain Persons knowledge experience expectations The use of preexisting knowledge to organize individual features into unified whole o Guided by higher level cognitive processes such as knowledge and expectations Top down processes influence how we perceive objects o Example the multiple personalities of a blob Object Perception Four concepts o Helmholtz s unconscious inference o Regularities Approach o Bayesian inference o Gestalt laws Unconscious inference The problem Stimulus on receptors can be ambiguous The solution Helmholtz s Theory of Unconscious Inference 1860 o We perceive the object that would most likely cause the pattern of stimulation o Termed the likelihood principle Perceptions are the result of unconscious assumptions we make about the environment o We use our knowledge to inform our perceptions o Top down processes help us interpret the signal Regularities in the environment Similar to Helmholtz s idea of unconscious inference This approach suggests that perception is influenced by our knowledge of regularities in the environment Semantic Regularities characteristics associated with the functions carried out in different scenes o Scene Schemas Physical regularities regularly occurring physical properties of the environment o Oblique effect we are biased to perceive vertical and horizontal orientations because those are more frequent than other orientations Light from above assumption Good continuation perceive covered object as continuous in form Object Recognition Perceptual set perceptual expectancy o The tendency to perceive things a certain way because previous experiences or expectations influence those perceptions o Our experiences create schemas Schemas can bias our perceptions Bayesian Inference Unconscious inference and regularities in the environment lead to a third approach based on probabilities Based on o Prior probability initial belief regarding probability of an outcome o Likelihood of the outcome extent to which available evidence is consistent with the outcome Gestalt Psychology A perspective proposed around the time of Helmholtz s theory of unconscious inference o A shift away from structuralism Whole is greater than the sum of its parts Principles of perceptual organization explains how we group objects Law of Pragnanz o Individuals organize their experience in as simple concise symmetrical and complete manner as possible Gestalt and regularities in the environment The Gestalt principle of good continuation is likely related to the fact that object continuations occurs in the environment Perception and action Action facilitates perception Gibson o Movement helps us perceive objects in the environment more accurately What and where streams o What Ventral stream Identifying an object AKA Perception Pathway o Where How Dorsal stream Identifying the objects location AKA Action Pathway Neurons and the environment Neurons becomes tuned to respond best to what we commonly experience o Horizontals and verticals Change Detection Flicker paradigm o Blank intermediate image o Distrupts attention Draws attention away from scene Serial Search Increased reaction time Uninterrupted image o Pop out effect o Decreased reaction time Importance of attention in perception o Interactive processes Change blindness


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