Infradian rhythms are biological rhythms lasting more than 24 hours e.g. the menstrual cycle which is regulated by the secretion of oestrogen and progesterone over a month. It was originally thought to be controlled by the hypothalamus acting as an endogenous pacemaker. But, evidence shows external zeitgebers play a role. Another example is PMS which occurs a few days before menstruation and is characterised by loss of appetite, stress and poor concentration.
Russel et al used sweat of donor women causing other female participants menstrual cycles to become synchronised with that of the donor suggesting exogenous zeigebers influence a women's infradian rhythms and that endogenous pacemakers and exogenous zeitgebers interact to control infradian rhythms. However, a small sample was used and results may have occurred due to random occurrence raising issues of validity of findings. But, other research has found similar findings suggesting it is reliable and valid. The women used in the study has similar length menstrual cycles which may have acted as a confounding variable in whether their infradian rhythms synchronised or not, evidence of women with different length cycles synchronising would be needed to increase the external validity of findings. This study is reductionist and only focuses on the role of hormones and other factors such as the environment are ignored. Such factors may have acted as confounding variables influencing the menstrual cycle and thus the women's infradian rhythms.
Issues occur into research especially regarding PMS, as this has cited as a mental disorder and used as legal defence e.g. Ms English drove her car into her partner after an argument, killing him, using PMS as legal defence resulting in her being put on probation. Such anecdotes are deterministic and suggest women have no control over their behaviour when influenced by such infradian rhythms. This could result in responsibility being taken away from women who behave aggressively, and violent women being acquitted for violent acts.
Ultradian rhythms are biological cycles that last less than 24 hours. An example of this is the stages of sleep. Stages one and two are light sleep, heart rate reduces and muscles relax. Stage two also has noticeable sleep spindles and K-complexes. In stage 3 sleep spindles decline being replaced by delta waves. Stages 3 and 4 are slow wave sleep (SWS). Stage 4 is deep sleep, delta waves increase and metabolic rate is low. It takes about an hour to pass through stages 1-4 and after 90 minutes after falling asleep REM is entered. As the night progresses more time is spent in REM. This is fairly universal but there are developmental differences.
Dement and Klietman found participants when woken during REM sleep dreaming was reported 90% of the time and was recalled in detail. Only 7% reported dreaming in NREM. EEG recordings were used in order to wake participants up during different stages of sleep providing results with higher reliability and validity as researcher could determine which stage of sleep participants were in. From findings it could be assumed that REM sleep is dreaming sleep. However, this assumption is reductionist assuming all individuals will experience that same ultradian rhythms. Dreaming was not always reported in REM, additionally dreaming was reported in NREM although not as frequently. Results were inconclusive meaning the REM dream link is still unclear and that further research is needed in order to gain a better understanding of why dreams occur within this ultradian rhythm.
Russell, and Dement and Kleitman's research provides us with evidence of internal infradian and ultradian rhythms which help control cycles within the body. Such research is mostly conducted in a laboratory setting which lacks external validity as results may not generalise to real life settings. However, research has a piratical application to help us gain a better understanding of how our biological rhythms work. This may aid in providing better treatment for those who cannot synchronise rhythms or have difficultly controlling behaviour because of them.
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