infradian rhythms

• how long does an infradian rhythm last?

  more than 24 hours.
• what is an example of an infradian rhythm?

  the menstrual cycle
• Infradian rhythm research - McClintock (1971)

  he kept a record of 135 participants menstrual cycles, as they lived in a women's college from September until April. their cycle ended up syncing. he believed this was due to their pheromones.
• evaluation of McClintock (1971) - infradian rhythms

  this suggests that pheromones are important in regulating the menstrual cycle. therefore exogenous factors play a role, as well as endogenous ones. however, pheromones were not directly investigated in this study.
• infradian rhythm research - Russel et al (1980)

  they applied the pheromones of one women to a group of sexually inactive women. a swab was taken from the donors armpit daily, the pads were alcohol to remove any bacteria and then rubbed on to the upper lips of the sexually inactive women. he found that 4/5 synced with the 'odour donor', confirming that pheromones have a role in syncing the menstrual cycle.
• evaluation of Russel et al (1980) - infradian rhythms

  this study is an advancement on McClintocks study. the experimental design had high levels of control over potentially confounding variables such as sexual activity. this means a causational relationship can be established. however, the sample size was small which makes it difficult to generalise beyond the study. it also gave no explanation on why one person did not respond to the pheromones. this study is, however, consistent with the explanation that the role of pheromones is to give evolutionary advantage.