Distractibility, circadian arousal, and aging: A boundary condition?

Two studies assessed the presence of a synchrony effect between peak circad ian arousal and time of testing for both older and younger adults. Particip ants performed a reading aloud task that included distracting words that we re either present or absent and, if present, were either thematically relat ed or unrelated to the target text. As well, the distracting material was p resented in either spatially predictable or unpredictable locations. In eac h experiment, older and younger adults were tested at optimal versus nonopt imal times. Both experiments showed age differences in susceptibility to di straction, replicating earlier findings (e.g., M. C. Carlson, L. Hasher, R. T. Zacks, & S. L. Connelly, 1995). Neither showed differences due to time of testing, suggesting a boundary condition for cognitive disruptions assoc iated with circadian arousal patterns.