BACKGROUND/STUDY CONTEXT: Older adults' peak performance on memory and cognitive inhibition tasks tends to be in the morning, whereas younger adults' peak performance tends to be in the afternoon. Although these tasks require efficient attentional processes for optimal performance, previous research examining age differences in the effects of time of day has not measured the distinct aspects of attention quantified by the Attention Network Test (ANT; Fan, McCandliss, Sommer, Raz, & Posner, 2002, Journal of Cognitive Neuroscience, 14, 340-347).
Methods: The authors examined the relationship between time of testing and the efficiency of alerting, orienting, and executive attention networks by randomly assigning younger (18-28 years; n = 27, M = 21.37 years, SD = 2.39) and older (65-85 years; n = 32, M = 73.34 years, SD = 5.18) adults to morning (AM) or afternoon (PM) testing of alerting, orienting, and executive attention. Mean reaction times for each network were analyzed with a univariate analysis of variance (ANOVA) with age (younger, older) and time of day (AM, PM) as between-subjects factors.
Results: Consistent with the authors' hypotheses, although time of day had little effect on orienting or executive attention, it affected alerting in opposite ways for younger and older adults, with alerting cues benefiting performance most at participants' off-peak times of day. A larger benefit from alerting cues was observed when participants were tested at their off-peak (M = 30.11 ± 15.66) relative to their peak (M = 2.18 ± 15.97) time.
Conclusion: These findings show that age-related circadian patterns influence the alerting component of attention, with both age groups showing the largest benefit from alerting cues when testing occurs at nonoptimal times of day. Overall, these findings underscore the importance of controlling for time of day in investigations of attention and add to our understanding of how age differences in circadian patterns impact attention.