infradian rhythms

• infradian rhythms


  last longer than 24 hours and can be weekly, monthly or yearly
• monthly

  • female menstrual cycle
  • regulated by hormones that either promote ovulation or stimulate the uterus for fertilisation
  • ovulation occurs roughly halfway through the cycle when oestrogen levels are at their highest, and usually lasts for 16-32 hours
  • after ovulatory phase , progesterone levels increase in preparation for the possible implantation of an embryo in the uterus
  • important to note that although the usual menstrual cycle is around 28 days, there is considerable variation, with some women experiencing a short cycle of 23 days and others experiencing longer cycles of 36 days
• mcclintock


  mcclintock:

  • believed that womens menstrual cycles are controlled by pheromones
  • 29 women with a history of irregular periods
  • samples of pheromones were gathered from 9 of the women at different stages of their menstrual cycles, via a cotton pad placed in their armpit.
  • pads were worn for at least 8 hours to ensure that pheromones were picked up
  • pads were treated with alcohol and frozen, to be rubbed on the upper lip of other Ps
  • day 1, pads from the start of the menstrual cycle were applied to all 20 women
  • day 2, they were all given a pad from the second day of the cycle etc
• mcclintock - findings


  findings:

  • found that 68% of the women experienced changes to their cycle which brought them closer to the cycle of their 'odour donor'
• dalton


  • summarised many studies of behaviour change which could ne attributed to the menstrual cycle
  • 63-84% of crimes committed by women occur in the pre-mestrual period; accident and suicide rates increase, while there is a decline in the standard of schoolwork, in scores of intelligence tests and in speed of response
• infraradian rhythms - seasons

  research has found seasonal variation in mood where some people become depressed in the winter, which is known as seasonal affective disorder (S.A.D)

  • is an infraradian rhythm that is governed by a yearly cycle

  psychologists claim that melatonin, which is secreted by the pineal gland during the night, is partly responsible

  • the lack of light during the winter months results in a longer period of melatonin secretion, which has been linked to the depressive symptoms
• reinberg


  reinberg:

  • examined a woman who spent 3 months in a cave with only a small lamp to provide light
  • noted that her menstrual cycle shortened from the usual 28 days to 25.7 days
  • results suggest that the lack of light (an EZ) in the cave affected her menstrual cycle, and therefore this demonstrates the effect of external factors on infraradian rhythms
• russell et al.


  russell et al.:

  • found female menstrual cycles became synchronised with other females through odour exposure
  • 1 study, sweat samples from one group of women were rubbed onto upper lip of another
  • 2 groups were separate, but menstrual cycles synchronised
  • suggests that synchronisation of menstrual cycles can be affected by pheromones, they effect people nearby rather than on the person producing them
• russell et al. - conclusion

  conclusion:

  • these findings indicate that external factors must be taken into consideration when investigating infradian rhythms and that perhaps a more holistic approach should be taken, as opposed to a reductionist approach that considers only endogenous influences