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?
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
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
Parts vs. Wholes
– We see wholes, but the visual system initially sees parts (i.e. features) of objects
“Early parsing of the visual field is mediated by separate properties, not by particular combinations of properties”
What does Treisman conclude from this observation?
• “Analysis of properties and parts precedes their synthesis”
• What is the “strong prediction” Treisman makes?
Illusory Conjunctions
• Illusory conjunction - when perceived combination of attributes was not present
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
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
Search Slope
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Distractors
Response Time (ms)
Search Slope
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Parallel Search Serial Search
Visual Search
• Search Slopes can be flat for targets defined by:– color– orientation– curvature– motion– depth
• What does this imply about these features ?
Search Asymmetry
• 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?