To evaluate the nap duration that achieves maximal cognitive gain with practicality of implementation, the present work employs a within-subject design comparing nap durations of 10 minutes, 30 minutes, and 60 minutes with a no nap condition on benefits to alertness, vigilance, mood, speed of processing and memory over post-nap intervals of 5 minutes, 30 minutes, 60 minutes and 240 minutes. The effect of nap duration on memory encoding will also be examined.

Naps are a global phenomenon and a commonly adopted lifestyle countermeasure to reduce sleepiness and performance impairments. Experimental studies have also shown that naps can improve cognitive functioning and enhance memory and mood. However, the implementation of naps is highly varied amongst individuals, and it remains uncertain what duration of naps achieves the greatest cognitive benefit. Given the potential for naps to boost productivity in societies such as ours where insufficient nocturnal sleep is prevalent and where work hours are long, an investigation of the optimal nap duration is warranted.

Previous studies suggest that the benefits of brief naps (5-15 minutes) occur immediately after the nap and last a limited period (1-3 hours). Longer naps (>30 minutes) are more likely to produce some temporary decrements due to sleep inertia but have the potential to improve cognitive performance for a more sustained period. These findings need to be strengthened through replication and extended to include memory measures that are evaluated over a longer post-nap testing period. To evaluate the nap duration that achieves maximal cognitive gain with practicality of implementation, the present work employs a within-subject design comparing nap durations of 10 minutes, 30 minutes, and 60 minutes with a no nap condition on benefits to alertness, vigilance, mood, speed of processing and memory over post-nap intervals of 5 minutes, 30 minutes, 60 minutes and 240 minutes. The effect of nap duration on memory encoding will also be examined.

The investigator's findings are expected to inform theoretical models of sleep and cognition and will aid in the design of practical lifestyle strategies to alleviate sleepiness and improve cognitive performance that may be adopted in an everyday context to boost societal well-being and productivity.

Inclusion Criteria:

• Participants aged from 21 - 35 years and who have an average sleep duration of 6-6.5 h are eligible for this study.

Exclusion Criteria:

• Participants who have an average sleep duration of less than 6 h or more than 6.5 h, who report sleep apnea symptoms, who report drinking more than 5 cups of caffeinated drinks a day, who have a BMI greater or equal to 30, or report elevated depression or anxiety symptoms will be excluded.