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Abstract:
Variability is a known factor in aging studies. What is less
known is whether individual subjects are more variable and what
affect this may have on attention. We examined inter- and
intra-subject variability on a sustained attention task which
requires that key press responses be withheld to rare (one in nine)
targets. Subjects were tested on four consecutive days which
alternated between morning and evening sessions. There was no
effect of time of day. Analyses of reaction times preceding and
following rare target stimuli reveal increasing reaction times
before a correctly withheld response followed by significantly
faster responses. Both young and old subjects respond faster to
nontarget stimuli prior to making an incorrect response to targets;
old subjects, however, show increased reaction time following an
error while young subjects show little change in their reaction
times. Measures of variability reveal that while both young and old
subjects show greater variability in the reaction time following an
incorrect response to rare targets, old subjects show greater
overall inconsistently in their responses and the greatest
variability on trials just following false alarms to the targets.
These results indicate that older subjects do perform more
inconsistently than younger subjects and may employ different
strategies when attempting to sustain their attention on this
task.
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