... Circadian arousal patterns affect explicit and implicit memory differentially depending on the time of testing (May, Hasher, & Foong, 2005). Explicit memory, that is, conscious recollection of previous experiences (Graf & Schacter, 1985), is better when tested at on-peak times of circadian arousal (Baddeley, Hatter, Scott, & Snashall, 1970;Hasher, Chung, May, & Foong, 2002;Intons-Peterson, Rocchi, West, McLellan, & Hackney, 1998;May, Hasher, & Stoltzfus, 1993;West, Murphy, Armilio, Craik, & Stuss, 2002;Yang, Hasher, & Wilson, 2007). In contrast, implicit memory, that is, performance facilitation in the absence of conscious recollection (Graf & Schacter, 1985;Schacter, 1987), may be better when tested at off-peak times of circadian arousal (May et al., 2005). ...