Visual Search: finding a single item in a cluttered visual scene

Visual Search Serial search: each item is selected until target is found

Visual Search Serial search: each item is selected until target is found

Visual Search Serial search: each item is selected until target is found

Visual Search Serial search: each item is selected until target is found

Visual Search Parallel search: like many independent spotlights

Visual Search Parallel search - search time is independent of distracter number

Visual Search Serial Search - linear increase in search time with number of distractors

Visual Search Conjunction search: NOT FLAT!

Illusory Conjunctions Q 4

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 This binding process is thought to require attention focused on the location of the object to be bound

Treisman’s 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 Focused attention is required to “bind” features together into objects

Feature Integration Theory What term does Treisman use to describe the bundle of features at a specific location?

Feature Integration Theory Object Files are mental (neural?) representations of the features associated with an object –whenever an object is selected by attention its features are bound and an object file is “opened” –when the features of that object change, the object file is updated

Feature Integration Theory How did Treisman et al. test whether the visual system uses object files?

Feature Integration Theory Priming: observers are faster to respond to something they’ve just seen Prediction: if visual system is “object oriented” then priming effect should be attached to objects even when they move around

Feature Integration Theory +

+ G N

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+ G

What Letter?

Feature Integration Theory Compare “primed” box with “unprimed” box. What was the result?

Feature Integration Theory What was the result? –Naming was faster if the prime occurred in the same box, even though the object had moved –Priming isn’t locked to the location of the prime itself

Feature Integration Theory What was the result? –Naming was faster if the prime occurred in the same box, even though the object had moved Interpretation?

Feature Integration Theory What was the result? –Naming was faster if the prime occurred in the same box, even though the object had moved Interpretation? –visual system establishes object files (e.g. a box with a G in it) and updates them as the location and features of the object change –It is faster to make small changes than large changes

Attention and Consciousness Sensory information must be attended for it to be entered into awareness

Attention and Consciousness We’ve seen how orienting and selection interact to enable enhanced perception Enhanced perception includes awareness Thus attentional selection is the gateway to consciousness

Attention and Consciousness The attention orienting mechanism can be confused leading to something called “change blindness”

Attention and Consciousness Change blindness –Change blindness shows us that the feeling of being in a detailed visual environment is really just an illusion –We only have access to the parts of the scene to which we have attended

Attention and Consciousness Change blindness –Change blindness shows us that the feeling of being in a detailed visual environment is really just an illusion –We only have access to the parts of the scene to which we have attended –And that is often not very much!