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Next Week Memory: Articles by Loftus and Sacks (following week article by Vokey)
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Features and Objects in Visual Processing
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The Waterfall Illusion
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The Visual World is an Arrangement of Features Color Motion Form Depth Orientation
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Pre-attentive vs. Attentive Processing Pre-attentive processing –Does the visual system register some basic features automatically (without attention) –if so, what features? –How would you know?
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Pre-attentive vs. Attentive Processing Indicators of Pre-attentive processing –1. processing precedes orienting - if you shift your attention to something or someplace because of some processing you did on the information there, you must have done that processing without attending
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Pre-attentive vs. Attentive Processing Indicators of Pre-attentive processing –2. processing done in parallel - if you can process features of several objects simultaneously, you must have done that processing without attention
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Parts vs. Wholes –We see wholes, but the visual system initially sees parts (i.e. features) of objects
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Parts vs. Wholes For example:
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Parts vs. Wholes Simple features form boundaries
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Parts vs. Wholes Conjunctions don’t form boundaries
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“Early parsing of the visual field is mediated by separate properties, not by particular combinations of properties”
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What does Treisman conclude from this observation? “Analysis of properties and parts precedes their synthesis” What is the “strong prediction” Treisman makes?
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Illusory Conjunctions “errors of synthesis”
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Illusory Conjunctions Identify the letter on the left of the screen and the digit on the right
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Illusory Conjunctions Q 4
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What colored shapes did you see?
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Illusory Conjunctions Illusory conjunction - when perceived combination of attributes was not present
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Illusory Conjunctions Illusory conjunction - when perceived combination of attributes was not present Supports notion that primitive features are processed independently and then bound together to form objects
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What’s another way to investigate pre-attentive feature processing?
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Visual Search…why?
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Visual Search Parallel search - indicates pre-attentive processing of the feature that distinguishes target from distractors Serial search - indicates the target/distractor difference is processed only with the help of attention Parallel Search Serial Search
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Visual Search Search Slopes can be flat for targets defined by: –color –orientation –curvature –motion –depth What does this imply about these features ?
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Visual Search But there are some caveats: –What is a search asymmetry?
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Search Asymmetry
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But it’s the same discrimination…gaps vs. non-gaps !? What model does Treisman propose to explain search asymmetry along with other aspects of visual search?
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Feature Integration Theory Early visual system parses scene into features represented in “feature maps” “Attention Spotlight” can be moved across an overlay of these feature maps to bind features together
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