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The definition of attention has been __. As __ __ said, '____'. We know how it feels __.
- William James
- 'everyone knows what attention is'
- like subjectively
What are the two types of attention and which one are we focusing on? Are the two usually the same?
- Overt: physiclaly move in order to process one object/region preferentially (moving eyes etc)
- Covert: paying attention without moving the eyes
- We are focusing on covert
- Often the two select the same objects and regions
- BUT, as Hermann von Helmholtz showed, we can covertly select some objects and ignore others with attention independently from eye movements
Who's seminal study revived attention research? What was discovered?
- Cherry (1953)
- Dichotic listening task
- Two messages presented simultaneously in both ears - subjects repeat back one of the messages heard (shadowing experiment)
- Had little difficulty in doing this task --> showing that they can attend to only one ear consciously
- Little was remembered about the unattended message (esp detailed characteristics such as language and semantic content) but certain physical characteristics (like pitch, loudness,location) were recognised.
- My idea: link between this attention phenomena of low-level and high-level features with the low/high distinction of parallel searching in vision?
What is the basic assumption/concept behind the idea of selective attention?
- That there is some 'bottleneck' mechanism in that we cannot consciously attend to all the sensory inputs we receive all the time.
- The different theories differ in terms of which information is selected to pass through this bottleneck.
What are the two models of selective attention you should know about?
- Broadbent's Filter Model (1958)
- Treisman's Filter Attenuation Model (1964)
Explain what Broadbent's Filter Model is.
- Suggested there was a bottleneck in processing
- All sensory info at a given time enters a sensory buffer
- One of the inputs go through filter based on physical characteristics
- Operates priror to contact of sensory info with memory, and thus prior to identification of this info
- To prevent processing overload in the later processes where full processing takes palce
Explain what Treisman's Filter Attenuation Model is.
- Attention filter is not absolute - it does not completely block ignored information but simply attenuates it
- From finding that subjects in shadowing experiments switched from one input to the other when message previously delivered on attended side got switched to other side.
Give 2 studies that seem to support Treisman's Filter Attenuation Model.
- Cherry (1953): cocktail party effect - subject's own name noticed even when presented in gnored sream
- Von Wright & colleagues (1975): word previously associated with electrical shock
- galvanic skin reponses found even when these words (or even similar words) presented on irrelevant side under shadowing conditions
- Both suggest salient stimuli can sometimes overwhelm the attenuation imposed on them by attention.
[Spatial Attention] Describe the study that seems to the support the spotlight attention theory.
- Posner (1980)
- Attention-cueing paradigm
- Endogenously (internally-driven) cued to right or left of a central fixation point --> by point of an arrow
- Faster to detect stimuli if they were validly cued, and slower if they were neutrally or even slower if invalidly
- Exogenous cues (stimulus-driven) - box flashing at possible location but no meaning
- 100ms - valid cue sped up RT, but 850ms (when there is enough time for saccade) it made RT longer.
- Inhibition of return: when there is valid exogenous cue, but interval is too long it is counter-productive, because attention move to opposite side automatically --> a searching spotlight. Encourages vision to not search one spot in an image --> USEFUL!
- Attention is a spotlight moving from one area of a scene to another. Stimuli falling within spotlight reach awareness more rapidly
What is the study relating to attention and sensitivity?
- Hawkins et al (1990)
- d' sensitivity (how easy it is to detect a stimulus from background events)
- Hawkins showed, attention-cueing paradigm, that d' (dee-prime) was higher than neutral when target was validly cued, and lower when invalidly cued.
Explain to me the zoom lens model and the experiment that went with it.
- Eriksen & Eriksen (1974)
- Flanker paradigm
- Subject presented with three letters side-by-side - asked to press left key when they see H or K; right key if S or C in the middle.
- Slower when the flankers are incongruent with response to target.
- However, if spacing of flankers increased above 0.5 retinal angle on both sides, the flanker effect decreased (almost same time to do incongruent and congruent)
- However, closer than 0.5 degrees and incongruent RT is much higher.
- Shows that we cannot ignore flankers nearer than 0.5retinal degree from target. Minimum size of zoom-lens must have approx 1 degree visual angle diameter.
Neurophysiology of attention. What is a good animal study to use?
- Moran & Desimone 1985
- Single-cell recording of visual cortex of monkey trained to attend to stimulus in one location of visual field and not the other.
- Response to unattended stimuli was much lower in V4 cells
- Cells in the striate cortex (V1) were unaffected
- Therefore, seem to suggest filtering happens in extrastriate visual cortex and these neurons may be responsible for ability to identify and remember certain properties of object out of many presented to in retina.
Explain the studies that show how attention seems to modulate cortical processing in the human brain.
- Cortical processing of motion
- Chaudhuri (1990)
- Subjects engaged in discrimination task superimposed on a moving background. Because subjects were not attending to the moving background, motion aftereffect was considerably reduced. Motion aftereffect seems to be susceptible to attentional mechanisms.
- Rees et al 1997Similar paradigm but measured V5 and V1
- Reduced motion aftereffect and reduced activity in V5 motion area (not reduced in V1)
- Cortical processing inhibited when not attended there?
- ALSO - low V5 activation when perceptual load was high (perceptual load theory)
What is Levie's theory of attention?
- Perceptual load theory (connected to Rees' study)
- Early or late selection depending on perceptual load - perception has limited capacity but operate automatically
- When perceptual load high --> early selection (no perception of unattended stimulus)
- Low perceptual load --> late perception
- Load determined the extent to which irrelevant distractors are processed
What 3 disorders should we know about in terms of attention?
- Unilateral neglect
- Balint's syndrome
- Unilateral extinction
- All associated with damage to right parietal lobes
[Disorders of attention] What is the neglect syndrome and give me some studies.
- Neglect of side of space opposite the lesion in temporal parietal junction (eg. will ignore food on left side of plate)
- Eglin et al 1989 - visual conjunction search
- Performance much better when stimulus on intact side. Eye movements almost alwyas on intact side. Search for stimulus on neglect side severely affected by distractors on intact side. Shows inability to move attentin from intact side to neglect side.
- Bisiach & Luzzatti (1978)
- Unilateral neglect patients asked to describe remembered/imagined scene. Description from neglact side omitted. When they were asked to imaigne themselves from the other side of the scene, they cannot describe the side they just did.
- Shows that they hold info of whole picture, but attention inhibits them from accessing certain info.
What is Balint's syndrome?
- Bilateral parietal damage
- Simultanagnosia - inability to see two objects simultaneously
- Fixity of gaze --> difficulty in switching attention between objects
What is unilateral extinction?
- Following similar damage to Unilateral neglect and often co-occurs
- Can perceive single object presented left or right
- When 2 objects presented, one on each side, only notice the right-hand object