Time of day preferences and resource allocation

Abstract

Previous studies have shown that circadian rhythms can have a significant impact on cognitive task performance (Bodenhausen, 1990; May, Hasher, & Stoltzfus, 1993), and that performance is better during participants’ optimal time of day for explicit memory tasks and for tasks where inhibition of responses is required. Researchers have concluded that deficits during one’s non-optimal time of day are due to inefficient inhibition (e.g., May & Hasher, 1998). However, previous studies have not sufficiently addressed possible changes in resource allocation, or the amount of resources that are allocated to the primary task versus the amount of resources used to actively inhibit distracting information, and how these changes might be influenced by chronotype and time of participation. One way to address this issue is to use dual-task methodology because past research has shown that when participants are asked to engage in two tasks concurrently, performance on one or both tasks suffers, presumably due to inefficient resources (e.g., Baddeley, 1996). Two experimental paradigms, the psychological refractory period (PRP) and explicit memory dual task, were used to investigate how time of day preferences affected changes in resource allocation. Results showed that, at least for college students, performance on these tasks was not more efficient during peak times, suggesting that optimal allocation of attentional resources does not rely on chronotype synchrony. However, further analyses suggested that synchrony effects may be masked by including Morning and Evening types in the same analysis, as opposed to separating the chronotypes when examining peak and off-peak groups. These two groups of participants showed a pattern of opposite effects in the current experiments, with only Evening types showing a trend towards synchrony. Given that the majority of previous synchrony effect results have been confounded by age, more research should be conducted to disentangle these two factors.