A study involving five experimental groups investigated the effects of naps, caffeine naps, naps combined with cold face/hand washing, and naps with bright light exposure on alertness, cognitive performance, and sleepiness.

“the study that comes to mind there was a brilliant investigation Herculean in its study design from a great sleep research group out in Japan and they asked okay the nap is good the caffeine nap may be a little bit better but can we go further um and so they designed a series of studies they had five different experimental groups and they tried to basically create a stack a stacking system they had across the 5 groups there was a non naap group that's the control then there was a nap group then there was a nap plus caffeine group then there was a nap Plus Cold face and cold handwashing immediately after you wake up I'll come back to explain why that we think that works and then the final group was a group that was a nap plus bright light”