Infradian and Ultradian Rhythms

• A strength of research into infradian rhythms is its practical application.
• For example, an effective treatment for SAD is phototherapy which is a lightbox that stimulates strong light in the morning and evening.
• This is thought to reset melatonin levels in the pineal gland.
• This strengthens both the applicability and support for research into infradian rhythms as phototherapy relieves symptoms in up to 60% of sufferers.
• A limitation of research into infradian rhythms is the existence of confounding variables.
• For example, it is argued that there are many factors that may affect the change in periods such as stress, diet and weight.
• These might act as confounding variables which suggests a lack of control of extraneous variables within Stern and McClinktock's study.
• This weakens both the internal validity and support for research into infradian rhythms given that any supposed pattern of synchronisation is no more than would've been expected to occur by chance.
• A strength of research into ultradian rhythms is evidence which supports quantitatively different stages in sleep.
• For example, Dement and Kleitman monitored sleep patterns of 9 participants and found evidence for the stages sleep, especially REM sleep.
• Participants woken during dreaming reported accurate recall of their dreams, which suggests that REM activity during sleep correlated with dreaming.
• This strengthens both the internal validity and support for research into ultradian rhythms as the study suggests REM sleep is a distinct ultradian rhythm.
• Another strength of research into ultradian rhythms is the methodology used in Dement and Kleitman's study.
• For example, they used brain scans to record the evidence and to monitor sleep patterns amongst all 9 participants.
• This means that the findings can easily be re-tested and replicated by other researchers.
• This strengthens both the reliability and support for research into ultradian rhythms as the methodology used is both empirical and objective, making it free from bias.