Describe and Evaluate Research studies into Infradian and Ultradian Rhythms (24 marks)
Infradian Rhythms repeat themselves over a greater period of time – rhythms that last longer than a day. For example, they may repeat themselves weekly, monthly or even annually (known as a circannual rhythm), for example, hibernation, bird migration and many reproductive cycles. One of the main human biological Infradian rhythms is the menstrual cycle.
Several research studies have been done into Infradian rhythms, and how to regulate them. Infradian rhythms are governed by endogenous pacemakers (internal cues) and exogenous zeitgebers (external cues). One zeitgeber that helps regulate Infradian rhythms is the release of pheromones; a biochemical substance produced in the endocrine system and distributed throughout the blood, which is then released into the air which often affects other individuals.
Research into these zeitgebers was carried out by Russell (1980) who used pheromones to synchronise women’s periods within a small group. He took the pheromones of one woman and applied them to a group of sexually inactive women by taking cotton pads from the armpit and rubbed them onto the group of women’s lips. It was found that 4 out of 5 women in the experimental group had menstrual cycles that synchronised within 24hours of the donor’s, as opposed to none in the control group. This suggests suggested pheromones act as exogenous zeitgebers and can influence endogenous pacemakers.
Russell’s research has empirical support from McClintock & Stern (1998) who set up a 10-year longitudinal follow-up study of Infradian rhythms, following Russell’s research using a bigger sample of 29 women with a history of irregular periods. It was found that 68% of women responded to the pheromones and their menstrual cycles changed dramatically up to 14 days to match the other synchronisation.
On the other hand, these results can be explained through other means and do not form conclusive evidence for zeitgebers affecting pacemakers within infradian rhythms. This is argued using a similar study testing a women’s basketball team for an extended period which found no correlation found between the infradian menstrual rhythm and pheromones, therefore suggesting that healthier women who play basketball are not prone to stress, weight issues or immobility which could otherwise act as unaccounted variables producing varying menstrual cycles, making Russell’s study low in internal validity.
In addition, a biological process such as the release of pheromones is an automatic…