Individual differences

• One further issue which complicates the generalisation of findings from studies of the sleep wake cycle is that individual cycles can vary in some cases from 13 to 65 hours (Czeisler et al 1999)
• in addition a study by Duffy et al 2001 revealed that some people display a preference for going to bed early and rising early whereas some people prefer to do the opposite
• There ate also age differences in sleep/wake patterns. According to neuroscientists teenagers‘ circadian rhythms typically begin two hours after those of adults