Infradian rhythms

• Infradian Rhythms - consistent cyclical variations over a period longer than 24 hours such as menstruation
• Research into infradian rhythms:

  Russel et al - applied pheromones of one woman to a group of sexually inactive women.

  A swab was taken from the donors armpit daily and the pads used were treated with alcohol to remove any bacteria and then rubbed onto the upper lips of the sexually inactive women.
• Research - Russel et al

  On day 1 - pads from the start of the menstrual cycle were applied

  On day 2 - they were given pads from the second day of the cycle and so on.

  Some women in a control group recieved the same treatment but using pads that had not collected perspiration. Participants did not know what group they were in.
• Findings from Russel et al

  At the end of the experiment it was found that 4/5 women in the odour group had menstrual cycles that had synchronised to within a day of the odour donor.

  This confirmed the role of pheromones in regulating the menstrual cycle.
• Research - McClintock

  Studied 135, 17-22 year old student women.

  They were asked to recall previous menstrual periods over the last year.

  They found that women who lived or spent a lot of time together had synchronised menstrual cycles. She also found that women who work with men have shorter menstrual cycles.
• Evaluation - McClintock

  Suggests pheromones are important in regulating menstrual cycles.

  Therefore exogenous factors play a role as well as endogenous ones. However pheromones were not directly investigated in this study
• Evaluation - Russel

  Advancement on McClintock study in measuring the direct impact of pheromones on synchronising women menstrual cycle.

  It used an experimental design with high levels of control over potentially confounding variables such as sexual activity and awareness of which group they were in. This means a causal relationship can be established.

  Sample size was small which makes it difficult to generalise beyond this study

  1/5 of the women did not respond to the donors odour