Aging and Visual Search

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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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INTRODUCTION
Display Size Effects for Experiment 2
Display Size Effects for Experiment 1
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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 Lavies (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. 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.
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Younger Adults
Older Adults
Younger Adults
Older Adults
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Reaction Time (ms)
Reaction Time (ms)
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Display Size
Display Size
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Distractor Effects for Experiment 2
Distractor Effects for Experiment 1
EXPERIMENT 1 Method

• Participants
• 32 younger adults (mean age 20 yrs, range 18-29
  yrs) and 32 older adults (mean age 68 yrs, range
  60-81 yrs).
• Stimuli and Procedure
• 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 oclock 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.

Experiment 1 Results
Experiment 2 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.

• 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.

EXPERIMENT 2 Method
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.

• Participants
• 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.

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Sample Displays for Each Trial Condition and
Display Size (the target is the letter C in each
display)
Acknowledgements This work was supported by
National Institute on Aging grant R37 AG02163.
Compatible
Incompatible

• The distraction from irrelevant items occurs
  prior to response selection The degree of
  disruption is comparable for response-compatible
  and incompatible items.
• Under these viewing conditions, the efficiency of
  selective attention is not compromised
  substantially by aging.

CONCLUSIONS

• Perceptual load and selective attention interact
  The disruption of performance from irrelevant
  items decreases as a function of increasing
  display size.

Neutral