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