Aschoff and wever

• Wever and Aschoff (1976) had a group of participants live in a WWII bunker for four weeks and found that the sleep/wake cycle lasted just under 25 hours for these participants concluding that external factos (light hours’/meal times) may have an impact mediating the cycle
• All but one of the participants (whose sleep/wake cycle extended to 29 hours) displayed a circadian rhythm between 24 and 25 hours
• both siffre’s experience and the bunker study suggests that the ‘natural’ sleep/wake cycle may be slightly longer than 24 hours but that it is entrained by exogenous zeitgebers associated with our 24-hour day