Evaluation

• Implication - role of exogenous zeitgebers

  • Stern and McClintock - 29 women with irregular periods
  • Samples of pheromones gathered from 9 of the women at different stages via cotton pad on armpit for 8 hours
  • Pads frozen and rubbed on top lip of 20 women
  • 68% of women experienced changes in cycles closer to donor's
  • Therefore, infradian rhythms also use exogenous zeitgebers
• Methodological issues

  • Many confounding variables in synchronisation studies
  • Any supposed pattern of synchronisation is no more than would have been expected to occur by chance
  • Explains why other studies (Trevathan et al.) failed to replicate findings
  • Therefore, studies are flawed, decreasing internal validity