Transcript Aging and Visual Search

Aging and Visual Search:
Interaction of Perceptual Load and Selective Attention
David J. Madden and Linda K. Langley
Center for the Study of Aging and Human Development, and Department of Psychiatry and Behavioral Sciences,
Duke University Medical Center, Durham, NC 27710
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EXPERIMENT 1
Younger Adults
Incompatible
Compatible
Neutral
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Sample Displays for Each Trial Condition and Display
Size (the target is the letter C in each display)
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H
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L D
X C B
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Q LT
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L D
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H
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Incompatible
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C
Display Size:
6
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C
R
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R
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C B
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L T
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B
R
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Younger Adults
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Older Adults
Incompat. - Neutral
Compat. - Neutral
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2
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Experiment 1 Results
 Error rates were comparable for younger adults (5.3%) and
older adults (6.4%).
 As depicted in Figure 2, search rates (display size effects)
varied as a function of age group. RT slopes were
significantly steeper for older adults (M = 60 ms/item) than for
younger adults (M = 48 ms/item).
 As depicted in Figure 3, there was an interaction of
perceptual load and selective attention effects. The distractor
effects diminished with increasing display size. RTs in both
the compatible and incompatible conditions were significantly
higher than RTs in the neutral condition, but only at display
sizes 2 and 4, not at display size 6. RTs in the incompatible
and compatible conditions did not differ significantly.
 Contrary to prediction, distractor effects did not vary as a
function of age.
EXPERIMENT 2
Method
Participants
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Display Size
Distractor Effects for Experiment 1
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Older Adults
Incompatible
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Display Size
 32 younger adults (mean age 20 yrs, range 18-29 yrs) and 32 older adults
(mean age 68 yrs, range 60-81 yrs).
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Display Size
 The task was a two-choice version of visual search in which one of four
target letters (H, C, S, or K) was present in the circular display on each trial.
 Participants pressed one response key if the letters H or C were present
and the other response key if the letters S or K were present.
 Each display also contained two distractor letters and either one, three, or
five nontarget letters.
 The two distractor letters were positioned at 3 and 9 o’clock within the
circle. Participants were instructed to ignore these distractors. Thus, the
number of relevant display items was 2, 4, or 6 (see Figure 1).
 The identity of the distractor was determined by the trial condition
(response-compatible, incompatible, and neutral). For example, if the
identity of the target letter was C, the distractors’ identity was H in the
compatible condition, S or K in the incompatible condition, and R in the
neutral condition.
 Following presentation of a warning signal (asterisk) for 500 ms, the display
appeared for 250 ms for younger adults and 750 ms for older adults.
Display offset was followed by a blank screen. For both younger and older
adults, 2500 ms from the onset of the display was allowed for the response.
Younger Adults
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Stimuli and Procedure
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Method
Participants
Older Adults
Reaction Time (ms)
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Display Size Effects for Experiment 2
Difference Score (ms)
We conducted two visual search experiments to explore the
Maylor and Lavie (1998) findings further. We included both
response-compatible and incompatible distractors to determine
whether the distraction was due entirely to response selection. We
also placed the distractors inside the display, to determine whether
distraction required the presence of a single item outside the
display configuration.
Reaction Time (ms)
Maylor and Lavie (1998) reported that age differences in
visual search are influenced by the interaction between perceptual
load and selective attention. The disruption of visual search
associated with response-incompatible distractors (presented
outside of the search display) decreased as the number of items in
the display (perceptual load) increased. This result was consistent
with Lavie’s (1995) proposal that selection occurs only when
capacity limitations are exceeded. Distraction effects were more
pronounced for older adults than for younger adults at lower levels
of perceptual load, but diminished more rapidly for older adults
with increasing load. Maylor and Lavie characterized their findings
in terms of (a) an age-related decline in inhibitory control, which
limited the efficiency of selective attention at lower loads, and (b)
an age-related reduction in processing capacity, which led to an
improvement in selectivity with relatively smaller increases in load.
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Display Size Effects for Experiment 1
Difference Score (ms)
INTRODUCTION
 24 younger adults (mean age 20 yrs, range 18-24 yrs) and 24 older
adults (mean age 70 yrs, range 60-81 yrs).
Stimuli and Procedure
 The task and procedures were the same as those used in Experiment 1,
except the display remained on the screen until a response was made or
10 sec had elapsed.
Distractor Effects for Experiment 2
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Younger Adults
Older Adults
Incompat. - Neutral
Compat. - Neutral
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Display Size
Experiment 2 Results
 The results of Experiment 2 replicated those of Experiment
1. Error rates were comparable for younger adults (2.4%)
and older adults (2.1%).
 Again, the display size effect varied between age groups
(see Figure 4). RT slopes were significantly steeper for
older adults (M = 123 ms/item) than for younger adults (M =
72 ms/item).
 Distractor effects again diminished with increasing display
size (see Figure 5). RTs in the compatible and
incompatible conditions were significantly higher than RTs
in the neutral condition at display sizes 2 and 4 but not at
display size 6. RTs in the incompatible condition were
significantly slower than those in the compatible condition
only at display size 4.
 Distractor effects did not vary as a function of age.
References
Lavie, N. (1995). Perceptual load as a necessary condition for selective
attention. Journal of Experimental Psychology: Human Perception and
Performance, 21, 451-468.
Maylor, E. A., & Lavie, N. (1998). The influence of perceptual load on age
differences in selective attention. Psychology and Aging, 13, 563-573.
Acknowledgements
This work was supported by National Institute on Aging grant R37 AG02163.
 The distraction from irrelevant items occurs prior to response
selection: The degree of disruption is comparable for
response-compatible and incompatible items.
 Perceptual load and selective attention interact:
The disruption of performance from irrelevant items  Under these viewing conditions, the efficiency of selective
decreases as a function of increasing display size.
attention is not compromised substantially by aging.
CONCLUSIONS