PSY20007 Week 6 Attention - Part 3 & 4 PDF

Attention III. Structural and Capacity Theories Readings Goldstein, ch. 4, pp. 99, 105, 106, 112-118 Norman, ch. 4 “A Capacity Model of Attention” Styles, ch. 7 “Divided Attention”  Learning Objectives Global Learning Objective  U...

Attention III. Structural and Capacity Theories Readings Goldstein, ch. 4, pp. 99, 105, 106, 112-118 Norman, ch. 4 “A Capacity Model of Attention” Styles, ch. 7 “Divided Attention”  Learning Objectives Global Learning Objective  Understand and explain the main theories, concepts, and findings in selective attention research from the the 1950s until the present  Understand and explain the complementary relationship between theories and experiments in attention research and the way each drives development of the other  Learning Objectives Today’s Learning Objectives  Explain why Moray (1970) believed his divided attention experiment was inconsistent with both late and early selection  Describe the difference between structural and capacity theories of attention  Explain what is meant by an Attention Operating Characteristic and how capacity theories predict "graceful degradation" of performance when attention is divided  Describe the strengths and weaknesses of capacity theories  Describe Posner's "spotlight of attention" metaphor and how its predictions are tested in cuing experiments  Describe three kinds of evidence for the existence of two different attentional control systems  Explain what is meant by "inhibition of return" and its significance for attentional control  Early vs. Late Selection Debate (1960s)  Developments from Filter Theory (Broadbent, 1958) Attention viewed as a selective filter to protect a limited-capacity system from overload Argument about what gets through the filter and where the filter is located  Summary of Evidence  Early Selection Theory  Filter before LTM  Evidence:  reduced detection accuracy on unattended channel (Treisman & Geffen, 1967)  Late Selection Theory  Filter after entry to LTM  Evidence: Semantic activation on unattended channel (McKay, 1973; Von Wright, Anderson & Stenman, 1975)  Early Selection Reply  Late Selection  Semantic activation on unattended channel shown by indirect means  Early Selection  Doesn't deny weak activation of semantic material on unattended channel. Indirect measures don't show it occurs to the same degree  ES: Weak semantic activation on unattended channel; LS: brief semantic activation on unattended channel. Really possible to distinguish?  Some phenomena not predicted by either?  Shadowing tasks investigate attentional filtering (try to exclude distracting material). Can study divided attention instead.  How well can we distribute attention across multiple channels? Cost of Divided Attention (Moray, 1970) Auditory signal detection: Pure tone stimuli. Selective: Monitor for targets on one channel only Exclusive OR (XOR): Monitor both channels, no simultaneous targets Cost of Divided Attention (Moray, 1970)  Inclusive OR (IOR): Monitor both channels, simultaneous targets possible  Compare simultaneous targets (AND trials) and nonsimultaneous (OR trials)  Moderate cost of divided attention (OR < SEL)  Large cost of simultaneous detection (AND < OR) Implications of Moray Study  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  (Target/nontarget distinction made in limited-capacity system, so if filtering occurs before this, distinction shouldn't matter) Implications of Moray Study  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  So not consistent with either early or late selection?  Maybe need a new kind of theory?  Structural and Capacity Theories (The 70’s View)  Two ways in which attention can limit performance:  Structural (Bottleneck) Theories  Some neural structures can only deal with one stimulus at a time  Competition produces processing “bottleneck” (filter theory)  (ES: bottleneck getting into LTM; LS bottleneck getting out)  Capacity (Resource) Theories:  Information processing is mental work  Work requires activation of neural structure  Limited capacity to activate structure  Capacity Theory (Kahneman, 1973)  Reduction of capacity produces deficit in divided attention tasks  Differs from structural theories because capacity can be allocated flexibly to simultaneous tasks  Interfering Effects of Divided Attention Strayer and Johnston (2001): Talking on a mobile phone interferes with driving (sharing capacity reduces accuracy and increases RT) 100 ms @ 60 km/h ~ 1.7 m  Dual Task Performance (Li et al., 2002) Attention demanding central task (letters same or different?) Easy or hard peripheral task (animal present? “Phase” of disk?) Difficult task much more affected by central load Capacity Theory Explains “Inattentional Blindness” Cartwright-Finch & Lavie (2007) – which arm of flashed cross is longer? Clearly visible square not detected Demanding central task uses all available capacity Study Capacity by Dual Task Trade-Offs  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 Auditory and Visual Dual Tasks Bonnel & Hafter (1998)  Easy auditory and visual tasks (detecting spot of light or tone) – triangles  Difficult auditory and visual tasks (discriminating increases from decreases in intensity of spot or tone  Difficult task trades off, easy one doesn’t  Different capacity demands  Pros and Cons of Capacity Theory (With Hindsight)  Value of capacity theory is new experiments it led to  Emphasises divided attention, flexibility of attentional control Shortcoming is its vagueness (can always come up with a capacity explanation)  Can make capacity theories mathematically precise using decision- making theories  Attention IV. The Control of Visual Attention Styles, ch. 4 “The Nature of Visual Attention” pp. 61-70 Styles, ch. 5 “Visual Attention” pp. 74-77 Goldstein, pp. 94-100  Attentional Orienting (1980s) First work on attention looked at auditory system (stereo tape recorders developed before visual displays) Also problem of eye movements:  Natural environment: movement in peripheral vision produces saccadic eye movement, greater visual acuity in foveal vision  Not interested in this! “Covert” attention – movement independent of eye movements Attention shifts precede eye movements and can occur without them Shifts of attention called attentional orienting  Posner: The “Spotlight of Attention”  Shifts of attention likened to moving spotlight  Selective enhancement for stimuli “illuminated by the beam”  Expresses selective, limited- capacity idea in spatial terms  Studying the Spotlight of Attention  Spatial Cuing Paradigm (Posner)  Attract attention to A, present stimulus at A or B, compare performance Spatial Cuing Paradigm Fixation Field (maintain central fixation throughout trial)  Spatial Cuing Paradigm Cue Field Wait for specified SOA (stimulus onset asynchrony) 100-300 ms  (Saccades take about 200 ms. Need to monitor eye movements at long SOAs, not necessary at short SOAs) Spatial Cuing Paradigm (Detection Target) Present stimulus Measure detection RT Cued (valid) trial: stimulus occurs at attended location Spatial Cuing Paradigm Miscued (invalid) trial: stimulus occurs at other location (with low probability) Spatial Cuing Paradigm Stimulus Field Uninformative cue (50% left, 50% right) Baseline to compare valid and invalid  Attentional Costs and Benefits Posner, Nissen, & Ogden (1978) 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 Costs and benefits can be due to: Switching Time Time to move the spotlight  Costs of disengaging from wrong location, benefit from engaging at correct location before stimulus Unequal Capacity Allocation  RT depends on capacity allocated to location  Neutral: capacity spread across locations; focused: capacity concentrated on one location Hard to test between these alternatives  Attentional Orienting  Natural environment: Shifts in attention can be top-down (decide to shift attention) or bottom-up (something captures attention)  Need both kinds of systems to function  Clinical patients show deficits of both kinds: failure to focus attention, failure to disengage attention  Two attentional control systems? How Many Orienting Systems? Endogenous  (voluntary) Exogenous  (reflexive) Two systems engaged by different kinds of cues One is cognitive (need to interpret); other direct, spatial (no need to interpret) Have different properties  Evidence for Separate Orienting Systems, I Different time course of central and peripheral cuing Peripheral effect peaks rapidly, central effect peaks slowly  Evidence for Separate Orienting Systems, II Different effects of load (Jonides, 1981) Voluntary orienting slowed by memory load; reflexive orienting is not Consistent with different capacity demands of two systems  Evidence for Separate Orienting Systems, III Inhibition of Return:  Found only with peripheral cues, not with central cues  What's the Purpose of Inhibition of Return?  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  Attentional Orienting Experiments  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  Combination of bottom-up and top-down control  Need to be able to focus attention, exclude irrelevant stimuli; also to respond to unexpected threats