Week 6: Structural and Capacity theories and Attentional Orienting Flashcards
Early selection theory VS Late Selection theory
Debate of where the filter is:
Before or after LTM (semantic mem)
Weak semantic activation on unattended channel
VS
Brief semantic activation on unattended channel
Cost of Divided Attention
(Moray, 1970)
description
Objective:
How well we can distribute/divide attention across multiple sources of information.
Dicrotic sounds
Different cases:
1) Selective . (SEL)
Monitor for targets on 1 channel (oneside)
2) Exclusive OR (XOR)
Monitor both, no simultaneous targets
3) Inclusive OR (IOR)
Monitor both channels, simultaneous targets possible
Comparing: simultaneous targets (AND trials) and non-simultaneous (OR trials)
Cost of Divided Attention
(Moray, 1970)
Discovery
SEL > XOR > IOR
67%) (54%) (OR: 52%; AND: 31%
Cost of Divided Attention
(Moray, 1970)
Implications
the findings were not in line with either theory:
Early Selection:
Predicts OR < SEL because there is attenuation with divided attention
Doesn’t predict AND < OR because attenuation shouldn’t depend on identity of stimulus:
the only thing that matter should be Target or nontarget but not that if they occur 2gether. so there shouldn’t be a dif.
Late Selection:
Predicts AND < OR because two simultaneous targets will both be selected by “pertinence” and compete to get through filter
Doesn’t predict OR < SEL because if there aren’t two targets, expect no competition
Structural and Capacity Theories:
2 ways tt attention can limit performance
1) Structural (Bottleneck) Theories
2) Capacity (Resource) Theories
Structural and Capacity Theories:
Structural (Bottleneck) Theories
1) Some neural structures can only deal with one stimulus at a time
2) Competition produces processing “bottleneck” (filter theory)
(ES: bottleneck getting into LTM; LS bottleneck getting out of LTM)
Structural and Capacity Theories:
2) Capacity (Resource) Theories
1) Information processing is mental work
2) activation of neural structure
3) Limited capacity to activate structure
Capacity Theories:
Kahneman, 1973
Focused Attention and Divided Attention:
Idea: we have a set amount of capacity (resources) and we have to allocate them and we can allocate them flexibly
Reduction of capacity produces deficit in divided attention tasks
Prediction:
there will be cost associated with dividing attention vs focused attention
Capacity Theories:
Cost of divided attention.
Strayer and Johnston (2001)
(real world example)
Talking on a mobile phone interferes with driving (sharing capacity reduces accuracy and increases RT)
100 ms @ 60 km/h ~ 1.7 m
Fraction of red lights missed: 0.03 increased to 0.07 (double)
Both tasks needs cog. capacity:
doing both simultaneously requires one to divide ones attention.
Capacity Theories: Cost of divided attention. Dual Task Performance (Li et al., 2002) Description & results central tasks
2 tasks:
1) a group of randomly arranged letters shown for a short while, identify if letters same or different (Attention demanding central task)
2) Easy/Hard peripheral task:
(identify for animal from pic (EASY) or ask for “phase of disk”(HARD))
Participants were measured on % correct.
Difficult task much more affected by central load
(90% VS 50%)
Inattentional Blindness:
Cartwright-Finch & Lavie (2007)
demanding central task
description and results
Participants asked to identify which arm of flashed cross is longer. (cross with blue(v) and green(h) line)
Clearly visible square not detected
Demanding central task uses all available capacity
Study Capacity by Dual Task Trade-Offs
curve (quater circle)
Attention operating characteristic (AOC)
Vary proportion of attention allocated to two tasks in dual task paradigm
“Graceful degradation” of performance as available capacity is reduced
Shape of trade-off curve tells us about capacity demands of tasks
Dual Task Trade-Offs:
Pros and Cons of Capacity Theory
new experiments it led to
Emphasises flexibility of attentional control
Shortcoming: vague (can always come up with a capacity
explanation) hard to falsify
Hindsight:
make capacity theories mathematically precise using decision-
making theories
Attentional Orienting
shift of attention
Issues of eye movement
Natural environment: movement in peripheral vision produces
saccadic eye movement, greater visual acuity in foveal vision
“Covert” attention – movement independent of eye movements
Attention shifts precede eye movements and can occur without them
Attentional Orienting likened to moving spotlight:
why? (2)
Enhanced Processing VS degraded processing
Selective enhancement for stimuli “illuminated by the beam”
Expresses selective, limited- capacity idea in spatial terms
Studying the Spotlight of Attention
Spatial Cuing Paradigm Attentional Costs and Benefits (Posner 1978)
description
Attract attention to A, present stimulus at A or B, compare performance: (Slide 21- 25)
Places
Fixation Field
Cue field (wait for specified SOA 100~300ms)
Present Stimulus: (left box or right box)
MEASURE RT
(Posner, 1978)
types of trials and results (3)
Valid: Cue same with Stimuli (80%)
invalid: Cue opp with Stimuli (20%)
neutral trials: both left and right r cued. used as Baseline to compare valid and invalid
(Posner, 1978)
results
Benefits:
Faster RT with valid
cue
Costs:
Slower RT with invalid
cued
Very flexible: can be used with RT or accuracy, and to compare all kinds of stimuli
Causes of Cuing Effects from the results of (Posner, 1978)
Costs and benefits can be due to:
1) Switching Time
2) Unequal Capacity Allocation
Costs and benefits of Cuing Effects:
1) Switching Time
Time to move the spotlight
Costs of disengaging from wrong location, benefit from engaging at correct location before stimulus
Costs and benefits of Cuing Effects:
2) Unequal Capacity Allocation
RT depends on capacity allocated to location
Neutral: capacity spread across locations; focused: capacity concentrated on one location
difficulty with finding the underlying causes of Effects between:
1) Switching Time
2) Unequal Capacity Allocation
Hard to test between these alternatives
Attentional Orienting: Orienting Systems (2)
1) Top-down (decide to shift attention)
2) Bottom-up (something captures attention)
Need to be able to focus attention, exclude irrelevant stimuli; also to respond to unexpected threats
Is there 2 attentional orienting control system? Observations
1) Need both kinds of systems to function
2) Clinical patients show deficits of both kinds: failure to focus attention, failure to disengage attention
Two systems engaged by
different kinds of cues
Endogenous(voluntary) VS Exogenous cues(reflexive)
Cognitive (Central cue; symbolic): need to interpret
Direct (Peripheral cue; spatial): 60ms
These 2 systems have different properties
Evidence for Separate Orienting Systems:
1) Different time course of central and peripheral cuing
Cuing Effect: MRTinvalid - MRTvalid
Peripheral effect peak < central effect peak
Peripheral effect peaks rapidly (100~150ms), central effect peaks slowly (300ms)
Thus using different processes (systems).
Evidence for Separate Orienting Systems:
Different effects of load (Jonides, 1981)
2 tasks:
1) Pri task: Retain Digits in mem (mem task)
2) Sec task: Detect spot of light cued/uncued location (Orienting task)
Voluntary orienting slowed by memory load; reflexive orienting is not
Consistent with different capacity demands of two systems
Inhibition of Return: defination and purpose
People respond more slowerly to stimuli at locations where they previously (at least 300 ms earlier) viewed a task-irrelevant stimulus
Ecological argument: Allows efficient search of complex environment.
Prevents repeated search of same location. Don’t need to maintain a “mental map” of locations that have been searched
Evidence for Separate Orienting Systems:
Inhibition of Return
finding
Facilitation(benefit) and Inhibition(cost) of short/long SOA
Mean RTs with peripheral cues and long SOAs are longer at cued locations than at miscued locations
If there is a delay of 300ms or more after a peripheral cue. target detection at that location is slowed down.
=>normally facilitatory effect has reversed to become inhibitory.
Found only with peripheral cues, not with central cues
Summary of Multiple sources of evidence for two systems
Effects of SOA and cue type: Reflexive system is faster, more transient; voluntary is slower, more sustained
Affected differently by load: Suggests voluntary system is under more cognitive control
Reflexive shows inhibition of return, voluntary doesn’t. Suggests reflexive controlled by different processes
