PSYC 213 - Chapter 3

PSYC 213 - Chapter 3 - 1 Chapter 3 Perception (pg.55-66) We...

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1 Chapter 3 – Perception (pg.55-66) We do not perceive perception as a complex task because of the ease with which we perceive o This idea initially misled scientists and it turns out that in reality it is very complex and that idea Perception depends on incoming stimulation as well as knowledge we bring in from situation Humans are better at perceiving than computers because they use perceptual intelligence o This is the knowledge they have gained from their experience in perceiving Perception is central to everyday experiences Bottom-Up and Top-Down Processing in Perception Behaviour is determined by energy reaching person’s receptors and by the knowledge person brings to situation o Ex: Ellen walking in forest – perceiving moth as a piece of moss at first Bottom-up processing : starts at stimulation of receptors and is crucial in determining experience – allowed Ellen to see the light reflected from moth which resulted in transduction process Ellen’s eyes at first detect a patch of dark light, she uses her knowledge of moths to come to the right conclusion Top-down processing: processing that involves person’s knowledge – Ellen uses knowledge to perceive and recognize moth o **it is a collaboration of both the bottom-up processing along with the top-down processing that results in perception The rat-man demonstration (figures 3.5 and 3.6 in text) show how recently acquired knowledge can influence perception Another example of top-down processing: experiment by Stephen Palmer (1975) o Used a context scene (kitchen counter) and flashed objects that where a) appropriate for scene (loaf of bread), b) misleading, as the object is shaped like the appropriate one (mailbox), c) totally inappropriate for scene, (drum) o Again the person’s knowledge of context influenced perception Recognizing Letters and Objects Template Matching: Led to the idea of perception based on features We compare the pattern to a model or template of object that is stored in system o When the pattern matches template there is recognition Caveat: even if object is tilted we can still recognize it Therefore the template-matching theory would require a template for every orientation of object and we can identify different forms of object See example 3.8 on page 61 re: the letter K Therefore this theory is not right – because we would need an astronomical number of templates to be able to identify objects Interactive Activation Model: (from chapter 2) we have cortical neurons called feature detectors that respond to line orientation
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2 This discovery led to the thought that the perceptual system constructs objects from simple features These features helps solve problem associated with template matching McClelland and Rumelhart developed the interactive activation model – says that activation is sent through 3 levels o Feature level: contains feature units – straight and curved lines
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This note was uploaded on 02/13/2011 for the course PSYC 213 taught by Professor Levitin during the Winter '08 term at McGill.

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PSYC 213 - Chapter 3 - 1 Chapter 3 Perception (pg.55-66) We...

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