Infradian rhythms

• What is an Infradian rhythm

  An Infradian rhythm is a rhythm that lasts longer than 24 hours to complete for example the Menstral cycle or seasonal affective disorder
• What is seasonal affective dissorder

  Seasonal affective disorder occurs during the winter months in colder? darker climates. It is characterised by depression like symptoms and a low activity and mood when deprived of sunlight
• What is the menstrual cycle

  The menstrual cycle typically takes 28 days to complete and involves rising levels of oestrogen which cause an egg to be released by the ovaries. Hormones steadily increase throughout the cycle until yje women experiences a period then the cycle begins again
• What is an endogenous pacemaker

  An endogenous pacemaker is an internal factor
• What is a exogeneous pacemaker

  An external factor
• What is synchronization

  The idea that women's menstural cycles can run at the same time this occurs between women in close proximity
• What was Stern and McClintock's (1998) research:

  Stern and McClintock investigated the extent to which the menstrual cycle is controlled by pacemakers or zeitgebers. They used a sample of 29 women, they collected sweat from 9 of these women over the course of their cycle. They applied the sweat from these women to the upper lip of the other women in the sample. Over time they found 68% of the women experienced changes to their menstrual cycle
• What was McClintock's (1971) research

  McClintock (1971) studied 135 women living in all-female halls at university. She found that those women who spent considerable time together reported that their menstrual cycles had become synchronised
• Research support of infradian rhythms

  Evolutionary theory could explain why synchrony happens. If females are synchronised, then they are likely to have offspring at the same time, therefore, they can share the energy and resources required to raise offspring. This will increase the survival rate of babies and potentially the mothers as well. Equally, any baby that loses a mother after childbirth may be able to survive if another mother is available
• Research limitation of infradian rhythms

  There are issues with small samples and cofounding variables in Stern and McClintock's study. For example diet, activity and lifestyle
• Application of Infradian rhythms

  Research into SAD has led to effective treatments such as light therapy, where individuals are exposed to certain frequencies of light, However, studies have found large placebo effects. It is possible that the belief that sunlight will make them feel happier has an effect on the mood of sufferers
• Research limitations of Infradian rhythms

  There is conflicting evidence for the idea that synchrony happens at all. Yang and Schank (2006) found in a sample of 186 Chinese women that there was no evidence of synchronization beyond that of chance