Perceptual load as a major determinant of the locus of selection in visual attention Lavie, N.,& Tsal, Y.(1994). Perception & Psychophysics, Vol.56(2), 183- 197.
Perceptual load as a major determinant of the locus of selection in visual attention
Lavie, N.,& Tsal, Y.(1994). Perception & Psychophysics, Vol.56(2), 183-197.
Overview
• Theoretical discussion – perceptual load
• Literature review – Early and late selection
• Conclusion
Background
• Broadbent (1958):– Early selection:
• Limited process• Analysis of physical features
Background
• Deutsch and Deutsch’s (1963):– Late selection:
• Unlimited process• Parallel• Relevant response
Background
• Kahneman and Treisman (1984):– Paradigmatic shift
• Filtering paradigm– Shadowing task (Cherry,1953)– Partial-report technique (Sperling,1960)
• Selective set paradigm–Spatial and semantic priming–Visual search experiment
Some debate about early selection
• Broadbent’s filter model – limited capacity channel
• Physical distinction rather than info load
• Clear physical distinction of relevant info is insufficient for early selection
• Lavie: – Physical distinction→priority→cannot prevent
irrelevant info processing
– Perceptual load of relevant info prevent irrelevant processing
The proposed model for selective attention
• Lavie’s premise:– Limited capacity :
• early selection• late selection (automatic process)
Literature review
• Structural approach
• Perceptual load
• Physical distinctiveness between relevant and irrelevant items
Literature review
Qualitative• Unlimited perception when
one irrelevant stimulus is processed
Quantitative• Limited perception but at the
same time can accommodate more than one item
• early selection =high perceptual load
• Late selection = low perceptual load
Perceptual load Operational definition
1. No. of units/items in the displayEx. A string of letters
word = 1 unitletters = many units
2. Nature of processing for each unit
Physical distinctiveness
• Major factor in determining nature of selection
• Focus on location• Low load – poor distinction / clear distinction
between target and distractor
Low perceptual load + poor physical distinction
• Poor distinction:– relevant and irrelevant stimuli occupy the same
location Ex. Stroop task
– Parallel processing of relevant and irrelevant dimensions
– Asymmetric interference. ex.: word → color
Low perceptual load + poor physical distinction
– Logan (1980): manipulate expectancy– Eriksens (1974):
• AUA AAUAA• irrelevant distractor is identified
Low perceptual load + poor physical distinction
– Eriksens and Schultz (1979):• Prolong the process of target→ increase
distractor effect
Low perceptual load + poor physical distinction
– Miller (1987):– Flank X target appear left– Flank O target appear right
• High correclation:88valid cue 8invalid cue• Low correclation:56valid cue 40invalid cue
Low perceptual load + poor physical distinction
Low perceptual load + poor physical distinction
– Lavie:• Low load→ spare attentional capacity→
irrelevant stimuli
Low perceptual load + poor physical distinction
– Paquet and Lortie (1990):• “+” attenuates associated-flanker effect• Spatial precue reduced distractor effect but not
eliminated it
Low perceptual load + clear physical distinction
• Eriksen (1974):– Contour-to-contour distance
• Keren, O’Hara, and Skelton (1977):– Same-different matching task– Flanking targets
• Tipper (1985):– Negative priming (NP)– Same identity, different shape(letter) → NP still
occurred
• Tipper & Cranston (1985):– Pictures and names → NP still occurred
• Distractor was processed to the semantic level• low load→ clear distinction→ irrelevant
processing
• Merikle and Gorewich (1979):– Size, distance→ incompatible distractor→
interfere
• Hagenaar and van der Heijden (1986):– Color patch→ compatibility
Manipulating display size Studies with high perceptual load
Manipulating display size
• Clearer evidence that early selection is found only under conditions of high perceptual load
1.Navon (1989)“possibility of early selection among all possible combinations of” physical properties {color , size} Semantic property {relevant item: letter / digit}
Items : letters + digits Low load display
• 2 item High load display
• 4 item
Distractor could be compatible / incompatible
1 Target ` 1 Distractor
1 Target ` 3 Distractors
Results
• Color = no effect of display size nor of distractor compatibility
• Category =display size interacted with distractor compatibility effect
2- item 4-item
• responses when the distractor was incompatible than when it was neutral or compatible
• Late selection
• No effect on distractor compatibility
• Distractor interference was reduced when the load was relatively high
• Thus early selection
2. Kahneman and Chajczyk (1983)“manipulated perceptual load in a variation of the stroop task”
• RT for naming color of a central patch appearing together with a black word directly above or below it.
Experiment.
Results• Word spelt a compatible color naming
responses were faster• Compatibility effect was reduced when:
1. second neutral word 2. array of Xs was added
• Reduction of attn. resources by neutral stimulus to capture incompatible distracting stimulus
• “Attn. resources are involuntarily allocated to irrelevant stimuli only when relevant processing is not sufficiently demanding.”
Possible extensions to other modalities (auditory)
Zelinker (1971)• Shadow list of digits (4)• Ignore feedback of their voices (0.2s delay)• 3 groups of shadowing
Results
Easy shadowing
Difficult shadowing
Resources interference
Delayed feedback difficult to ignore
More stuttering
Reduced interference
Barr and Kapadnis (1986)”manipulating difficulty of the relevant task affects the ability to ignore an irrelevant auditory message ”
• Standard shadowing test (English)• Native speakers and non native speakers
Results• Native speakers noticed more changes in
unattended channelEx. Speech interruptions reduction in voice intensity
• Changes caused more interferences in shadowing
• Non-native speakers resources processing of irrelevant message
SummaryEarly or late selection is determined by: 1) perceptual load 2)physical distinctiveness.
Early selection :– desirable perceptual loads ↑– possible when there is a clear distinction between
relevant and irrelevant items