Look Out—It's Your Off-Peak Time of Day! Time of Day Matters More for Alerting than for Orienting or Executive Attention

Abstract

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.

Acknowledgments

This research was supported by National Institutes of Health grants R01 AG025340 and K02 AG032309.

Notes

¹In contrast, Fernandez-Duque and Black (2006) observed a larger alerting effect in older relative to younger adults. However, this study incorporated a modified version of the ANT with larger stimuli and a longer duration for alerting, which may have contributed to the enhanced alerting effect in older adults. In addition, the error data suggest a more conservative response criterion for older adults may have also contributed to the larger alerting effect (Fernandez-Duque & Black, 2006).

²Answering the questions involved reporting today's date, naming the current and previous presidents, counting backwards by threes, repeating and later recalling and then recognizing three words the interviewer said, and describing how a dog and a lion are alike and how sugar and vinegar are different. Most participants answered all questions correctly. The one question some participants missed was the delayed recall for the three words (the most missed was two words). However, perfect performance on the recognition test that followed was required for the participant to be invited to come in for the session.

³All older adult participants completed the ANT. Of the 32 younger adult participants, data from 5 were excluded because of a computer malfunction that resulted in premature termination of the ANT.