Week Object-Based Attention & the Cognitive Neuropsychology of Attention

Question 1

What does attention act upon?

Answer 1

® Spotlight theory & feature integration theory assume that attention acts on a region of space – enhancing processing in that region.
® Object based theories suggest that attention acts on objects in space, not the space itself

Question 2

Rock and Gutman (1981)

Answer 2

 Overlapping figures: attend to one and rate aesthetic appeal; ignore other
 Memory test: good memory for attended figure, none for unattended figure (cf. Cherry, 1953)
 Objects occupy same region of space.
 Maybe the object of attention is the object, not the space it occupies?

Question 3

What Happens to the Unattended Shape?

Answer 3

 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)

Question 4

Tipper (1985, etc.)

Answer 4

-similar to rock and gutman but use regconisable stimuli
 Pairs of red-green figures: trumpet-kite, anchor-trumpet etc.
® Found that the RT to name the item (e.g. the trumpet) is slower if that object had been ignored on the previous trial. This is evidence of negative priming – where ignoring something previously makes you slower to respond to it than if you hadn’t seen it
® This also means that the ignored shape must have been perceived in order to produce an effect on the subsequent trial (consistent with late selection).
® This is evidence that people can attend selectively to one of two objects which occupy the same region of space.

Question 5

Implications of Rock & Guttman, Negative Priming

Answer 5

 Possible to attend to one object and ignore another when both occupy same region of space – how?
 Maybe attention operates on the object, not the spac

Question 6

Evidence for Object-Based Attention Duncan (1984

Answer 6

® Presented stimuli differing on 4 attributes – box size, gap side, line slant, dotted/dashed line.
® Flashed the stimuli briefly, and asked participants to report two of the attributes (e.g. line slant, gap side).

Question 7

Evidence for Object-Based Attention Duncan result’s

Answer 7

® Found that participants were more accurate if the two attributes belonged to the same object than different objects (same – box size and gap side or line slant and line style. Different – box size and line slant etc.).
- If you only have to report the attributes of one of the objects, then you only have to form a representation of one object and direct your capacity towards it versus forming representations of both and directing your capacity to both – which involves a cost of divided attention.
® He found these costs when stimuli were occupying the same region of space, which is evidence that attention operates on whole objects (rather than regions of space)

Question 8

Cuing Object-Based Attention (Egly, Driver, & Rafal, 1994)

Answer 8

 Miscued locations in same object or different object for the stimuli – same distance from cued location
 Space-based theories says miscuing costs should be the same
Same object advantage: Mean RTs faster to miscued stimuli if in same object
 Evidence that cuing effect spreads to encompass cued objects

Question 9

Effects of an Occluding Bar (Moore, Yantis, & Vaughan, 1998)

Answer 9

-Similar to Egly et al but with Occluding bar in stereo space to create a sens of depth.
-still find same object advantage
 Not related to crossing edges or boundaries; agrees with percept of continuous objects.

Question 10

Neuroimaging Evidence For Object-Based Attention

Answer 10

 Selective fMRI activation when viewing houses and faces. piture of two object fuse with each other
 Fusiform face area – active when viewing faces
 Parahippocampal place area – active when viewing houses
 Superimpose: attend to face or house
 Face: FFA up, PPA down; house PPA up, FFA down

Question 11

What is neglect

Answer 11

® Neglect refers to a deficit in processing spatial information

Question 12

Cause of visual neglect

Answer 12

® Damage to the right parietal lobe leads to left visual field neglect

Question 13

Attention and Visual Pathways

Answer 13

 Two pathways for processing visual information
 Ventral pathway, temporal lobe: form, colour – what pathway
 Dorsal pathway, parietal lobe: direction of motion, spatial location – where pathway
 Parietal lobe damage disrupts “where” pathway

Question 14

Neuropsychology of Neglect

Answer 14

 Not blind, but difficulty in making left side of space accessible to conscious awareness
 Right parietal lobe damage leads to left visual field neglect

Question 15

Way to show neglect

Answer 15

Neglect can also be demonstrated using the cancellation test, where people are asked to cross out line segments on a page. Neglect patients will omit the line segments on one side of the page.
Behavioural manifestations of neglect can often include a failure to dress the left side of the body, shave the left side of the face etc.

Question 16

Cuing Deficits with Right Parietal Damage (Posner)

Answer 16

 Compare intact and damaged hemispheres, use intact hemisphere as a control. show standard cuing effect but damage hemisphere is steeper
 Posner: normal attention involves engagement, disengagement, and shift (reorienting) of attention
 Ability to voluntarily engage attention not impaired; difficulties in disengaging and shifting in response to new information

Question 17

Symptoms of Neglect: Extinction

Answer 17

 Simultaneous identification of two stimuli
 Unimpaired with only one stimulus
 left visual field deficit with two simultaneous stimuli
 Perceptual response to one stimulus “extinguishes” response to the other. only able to know object in an unhinder region

Question 18

Why Does Extinction Occur

Answer 18

-Remember that Moray (1970) found that when two weak, simultaneous signals were presented, individuals had difficulties identifying both signals. This is consistent with late selection theory which suggests that only one signal can get through the filter to consciousness at a time
- Extinction shows that two competing perceptual representations cannot co-exist in consciousness of those with damage to the brain. This occurs because recognition & identification of objects requires activation of neural structures. The damaged hemisphere is chronically underactive, meaning stimuli don’t provide activation as they should. These effects are strongest with activity in the other hemisphere

Question 19

Balint’s Syndrome (Patient RM)

Answer 19

 Bilateral lesions in parietal and/or occipital cortex
 Inability to focus on individual objects and to see more than one object at a time (Simultanagnosia) – prone to illusory conjunctions
 Occurs even when objects overlap (Object based!)

Question 20

Space-Based and Object-Based Attention

Answer 20

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
 Tagging associated with objects, not just they space they occupy

Question 21

Object-Based Inhibition of Return (Tipper, 1991)

Answer 21

-Tipper rotated cueing markers to new locations, and then presented a target to be located in one of these markers.
-He found a slower RT at a previously cued marker, with inhibition of return tracking the cued marker to its new location.
-This shows that inhibition of return follows the cued object, and is not confined to one region of space. consistent with the idea that what is being inhibited is not just a region of space, but the perceptual object at that region of space (IOR is at least in part an object-based phenomenon)

Question 22

Object-based neglect (Behrmann & Tipper, 1994):

Answer 22

 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

Question 23

Object-Based Neglect (Behrmann & Tipper, 1994) rotation

Answer 23

Behrmann and Tipper’s display: present barbell, rotate 180 deg., present target to be detected
 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