Adult age differences in a visual search, luminance contrast discrimination task
Abstract
This thesis examined the ability of younger and older adults to use peripherally presented word
cues in a luminance contrast discrimination task. Observers were ten older adults (aged 55 to
69) and ten younger adults (aged 23-29). All observers were screened using the Wechsler Test of
Adult Reading and the Digit Symbol subscale of the Wechsler Adult Intelligence Scale (WAISIII).
Stimuli were presented on a 13 X 16° high-resolution monochrome monitor with an
average background luminance of 70 cd/m2. Target (distractor) stimuli were l°-diameter
luminance-incremented (decremented) discs. The spatial location o f the targets were cued using
luminance decremented ‘YES’ or ‘NO ’ words presented in 9 x 9 array prior to the presentation
of a 9 X 9 array containing one target and eight distractors that were positionally congruent to the
cued array. The discriminability (d') between target and distractors was varied and the contrast
increment threshold needed to just detect the target was calculated. Contrast increment
thresholds and mean correct yes response times were analyzed using a mixed two (Age Group) x
two (Sex) X three (Cue Validity) x two (Relevant Set Size) mixed ANOVAs. Pre-testing did
detect sensorimotor deficits in the older observers, but there were no significant main effects of
Age Group or Sex with respect to contrast increment thresholds or response time. Neither group
was able to take advantage of the word cues to allocate visual attention. In fact the sensitivity
and response times of all observers improved as cues became less informative. This suggests that
the ability to discriminate luminance contrasts is relatively preserved in older adults and that the
inhibitory effect o f the cues appeared to effect both age groups in a similar manner.
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- Retrospective theses [1604]