One fundamental aspect of attention is that it fluctuates from moment-to-moment, which manifests in performance variability. Increased variability in performance has been related to compromised functioning across many populations such as older adults and those with ADHD. Though previous studies have directly compared attentional fluctuations between groups of older and younger adults, they utilized small samples (N100) and the nuanced details of this developmental process have yet to be fully characterized. To address this, we administered the gradual onset continuous performance task (gradCPT), a sensitive sustained attention task, to a very large web-based sample (N4,000, testmybrain.org). The gradCPT requires participants to respond to the majority of stimuli (cities-90%) and withhold to rare target images (mountains-10%). The images gradually transition from one to the next every 800ms, which eliminates the exogenous effects of abrupt stimulus onsets and makes the task more reliant on intrinsic sustained attention abilities. The results demonstrate a highly significant positive relationship between age and reaction time variability that was best described by a quadratic function (adjusted R2=.20). Specifically, variability increased more rapidly with increased age. This age/reaction time variability relationship was significant after controlling for age-related changes in overall reaction time, response criterion, and accuracy, suggesting that it may be a unique aspect of aging. We also found substantial linear relationships between age and post-error slowing (R2=.17) as well as between age and caution towards erroneously pressing to mountain scenes (criterion C, R2=.10). Overall these results suggest two dissociable aging processes: a strategic, linear shift towards caution and reactivity to errors and a nonlinear increase in attentional fluctuations.
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