Week 8: Object-Based Attention and Cogitive Neuropsychology of attention Flashcards
What does attention Act Upon? (2)
Spotlight theory, assume attention acts on a region of space – enhances processing in that region
Alternative: attention acts on objects in space, not space itself: object based theories
object based theories:
Study 1
Rock and Gutman (1981)
Description (S3)
Overlapping figures (abstract)
Participants attend to one and rate aesthetic appeal; ignore other
Then given memory test:
Either on the red or green shapes without the colour, then asked did you study tt
object based theories:
Study 1
Rock and Gutman (1981)
Results (S3)
Good mem for attended figure (cf. Cherry, 1953 -> audio)
Objects occupy same region of space (unlike left right ear)
=> contradict the spotlight of attention, maybe pay attention for object, not space.
What happens to the Unattended Shape in Rock and Gutman (1981)?
Tipper (1985, etc.)
Maybe it’s not perceived or not fully perceived?
Maybe people quickly forget the stimulus they’re not attending to? – inattentional amnesia
(cf. early vs. late selection)
What happens to the Unattended Shape in Rock and Gutman (1981)?
Tipper (1985, etc.)
Negative priming
Pairs of red-green figures: trumpet-kite, anchor-trumpet etc (similar to Rock and Gutman just non-abstract figures)
Ignore green name red (e.g., ignore trumpet name kite)
What happens when trumpet must be named?:
RT to name trumpet is slower if ignored on previous trial
=>“Negative priming” (regular priming produces speed up)
Means ignored shape must have been perceived (recognised and cognitively registered to be ignored) to produce effect on subsequent trial (cf. late selection)
Maybe operating on object, not space
Implications of Rock & Guttman, Negative Priming
Possible to attend to one object and ignore another when both occupy same region of space
Maybe attention operates on the object, not the space
Evidence for Object-Based Attention
Duncan (1984) (s7)
Description
stimuli differing on four attributes: box size (big/small), gap side(right/left), line slant(right/left), style of the line(dotted/dashed)
Flash briefly, ask to report two of the attributes (e.g., line slant, gap side)
two groups:
1) Report 2 from same object (box/line)
2) Report 1 from each object
Evidence for Object-Based Attention
Duncan (1984)
Results
More accurate if the two attributes belonged to same object than different objects
Existence of benefit if belong to same object.
Stimuli occupy same region of space
Evidence that attention operates on the perceptual object, not the space.
Cuing Object-Based Attention
(Egly, Driver, & Rafal, 1994)
(S9)
Description and results
Conditions:
1) cued
2) Miscued same object
3) Miscued different object
the predictions:
Space Theory:
Faster for condition (1). the others would be similar as only space matter.
Object theory:
1) Faster for condition 1 and 2 as they belong to the same object compared to 3.
Cuing Object-Based Attention
(Egly, Driver, & Rafal, 1994)
(S10)
Results
Same object advantage: Mean RTs faster to miscued stimuli if in same object
Evidence that cuing effect spreads to encompass cued objects
Cuing Object-Based Attention with …
Effects of an Occluding Bar (Moore, Yantis, & Vaughan, 1998)
Description and results
Same as (Egly, Driver, & Rafal, 1994) with an Occluding Bar across the the 2 objects
Occluding bar in stereo space: still find same object advantage
Not related to crossing edges or boundaries; agrees with percept of continuous objects.
Neuroimaging Evidence For Object-Based Attention
Selective fMRI activation when viewing houses and faces
Fusiform face area – active when viewing faces
Parahippocampal place area – active when viewing houses
Superimpose: attend to face or house
Viewing Face: FFA up, PPA down;
Viewing House: PPA up, FFA down
Evidence that attention selects objects in space
possibly by enhancing representation of selected object; suppression of other object
Attention to part of an object benefits other parts
Neuropsychology of Attention:
Visual Neglect
Control of attention involves balance of top-down and bottom-up systems
Reflexive system orients to new stimuli, voluntary system provides sustained attentional focus
Failure to focus and failure to disengage and reorient both found in clinical cases
Damage to right parietal lobe -> deficits is lateralised
Attention and Visual Pathways
2 main streams (in the brain)
1) Ventral pathway, temporal lobe: form, colour – what pathway
2) Dorsal pathway, parietal lobe: direction of motion, spatial location – where pathway
Parietal lobe damage disrupts “where” pathway
Neuropsychology of Neglect
Deficit in processing spatial information
Not blind, but difficulty in making left side of space accessible to conscious awareness
Right parietal lobe damage leads to left visual field neglect
usually the results of stroke
Behavioural manifestations: failure to dress left side of body, shave left side of face, etc.
Neuropsychology of Neglect
Manifestations and tests
(drawing test - missing left side; Cancellation test)
Behavioural manifestations: failure to dress left side of body, shave left side of face, etc.
Neuropsychology of Neglect
Cuing Deficits with Right Parietal Damage (Posner)
Compare intact and damaged hemispheres, use intact hemisphere as a control
Posner: normal attention involves engagement, disengagement, and shift (reorienting) of attention
Mean RT:
1) Similar for valid cues
2) lot slower for INVALID Left visual field (Damaged) Vs Right visual field (Intact)
Ability to voluntarily engage attention not impaired; difficulties in disengaging and shifting in response to new information
==> also suggest that this is an attentional deficits not a visual one as it can be overcame by appropriately shifting attention.
Symptoms of Neglect: Extinction - definition
s20
perceptual response of to one stimulus “extinguishes” response to the other
Extinction: Two competing perceptual representations can’t co-exist
Symptoms of Neglect: Extinction
When does it occur?
Simultaneous identification of two stimuli
Unimpaired with only one stimulus
left visual field deficit with two simultaneous stimuli
Symptoms of Neglect: Extinction
Where else was it shown in;
Relevant to which theories
cf. Moray (1970): Normals poor in identifying two weak, simultaneous signals (audio) John Dunken (Vision) -> however need very hard stimuli to get it.
Late selection theory: Only one signal can get through filter to consciousness at a time
Symptoms of Neglect: Extinction
Why Does Extinction Occur
Recognition, identification require activation of neural structures
Damaged hemisphere chronically under-active, stimuli don’t provide activation they should
Effects strongest with activity in other hemisphere (invalid cue, competing stimulus)
Balint’s Syndrome (Patient RM)
where and symptoms
Edv for object based attention
Bilateral lesions in parietal and/or occipital cortex
Inability to focus on individual objects and to see > 1 object at a time (Simultanagnosia) – prone to illusory conjunctions (combining them 2gether S23)
Occurs even when objects overlap (Object based!)
Space-Based and Object-Based Attention:
Maybe it is a combination of both…
Linking both to Neuropsychology of Neglect
Attention seems mainly associated with “where” pathway
Spotlight view: movement of attention through space; neglect associated with left of perceptual space
Object-based view: attention keeps track of objects (“can ignore,” “shouldn’t ignore”)
Inhibition of return: cued spatial location tagged as uninteresting, so slower RT there (can this be shown for objects?)
Tagging associated with objects, not just they space they occupy
Object-Based Inhibition of Return (Tipper, 1991)
S25 to 29
Description
Standard IOR: peripheral cue, wait long SOA, flash target, slower RT at cued location
Object-based IOR: peripheral cue => then rotate display => Markers move to new locations
Measure RT to target in previously cued or miscued marker circle
Object-Based Inhibition of Return (Tipper, 1991)
S25 to 27
Results
Found slower RT at previously cued marker
Inhibition of return tracks cued marker to new location.
IOR follows the cued object, not confined to one region of space
Object-Based Neglect (Behrmann & Tipper, 1994)
Modified form Tipper 1991
S28 to 29
Rationale and methods
Neglect: left visual field deficit with right parietal damage
Neglect of space, or neglect of left side of object?
Barbell stimulus: two location markers + connector, combine into one perceptual object
Longer detection RT on left
(Control)
Behrmann and Tipper’s display: present barbell, rotate 180 deg., present target to be detected
Object-Based Neglect (Behrmann & Tipper, 1994)
Modified form Tipper 1991
S28 to 29
Results
Longer RTs on right
Neglect tracks marker to
opposite visual field!
Neglect of left side of objects, not just left side of space!
Allows space-based and object-based effects to be distinguished
Attention: The Take-Home Messages
Important interplay between theory and experiments: experimental findings suggest new theories to explain them; theories suggest new experiments to test them
Haven’t answered all the questions about attention
