Infradian Rhythms

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Created by
Shekinah Obare

Cards (7)

  • Infradian Rhythm
    Biological process that repeats less frequently than once every 24 hours. (eg weeks/months) Infradian = Infrequent.
  • Briefly outline two Infradian Rhythm’s
    • Seasonal affective disorder or (SAD), Takes a year to complete. Emotional mood lowers in winter and improves in summer. It is suspected this is due to the lack of bright sunlight in winter.
    • The menstrual cycle is a 28 day cycle with a 6 day period of fertility, however cycles can be shorter or longer ranging between 24 and 35 days.
  • Describe the biological process of the menstrual cycle infradian rhythm.
    Releasing the egg (ovulation), thickening of the womb lining and losing the womb lining during menstruation. These biological changes are regulated by the hormones oestrogen pre ovulation and progesterone post ovulation. The levels of these hormones act as endogenous pacemakers keeping the biological processes to time.
  • McClintock (1971) 

    Studied 135 women who lived in the same dorm at university, recording period onset and duration. Results showed women appeared to synchronise their cycles with their friendship groups. Other researchers have demonstrated similar findings when women cohabit (Russell 1980).
  • Stern and McClintock (1998) 

    Investigated if synchronisation was due to women sharing pheromones. 20 women given pads to wipe on their top lip each day. Pads had been taken from the armpits of 9 donor women at varying stages of their menstrual cycle. found that the women would either shorten or extend their menstrual cycle to match the donor’s cycle.
  • What counter research is there on McClintocks Infradian Rhythm findings
    Trevathan (1993) showing cohabiting lesbian couples did not synchronise, the optimal conditions for possible synchronization.
  • What alternative explanation is there for McClintock’s findings?
    As menstrual cycles can vary in length, women can appear to synchronise just due to their variability in their cycles, something not taken into consideration in all of the studies showing positive results.