Biological rhythms; Infradian and Ultradian rhythms
Infradian rhythms: Take longer than 24 hours to complete its cycle.
The menstrual cycle: Controlled by monthly changes in hormones which regulates
ovulation, a complete cycle is every 24-36 days. 1, the lining of the womb sheds 2, during
end of the cycle Oestrogen levels heighten during each cycle causing development of an egg
which becomes ovulated. 3, following ovulation, womb lining thickens for pregnancy (If
pregnancy does not occur, egg is absorbed into the body and lining sheds)
Related study: Stern and Mcclintock (2005)
Can menstrual cycles synchronise in response to exogenous factors? Studied 29 women with
history of irregular periods. Samples of pheromones collected from 9 of the women at
different times of the menstrual cycle (cotton bud under armpit). These pheromones were
rubbed on the upper lip of the other participants.
Day One: given pads from first day of menstrual cycle Day Two: given pads from second day
of menstrual cycle etc.
Results: 68% of women experienced changes to their menstrual cycle which bought them
closer to the cycle of their 'odour donor'.
Seasonal Affective Disorder (SAD): A depressive disorder diagnosed in the DSM-5.
has a seasonal pattern of occurrence, believed to be caused by lack of daylight hours
during winter months (winter blues). Causes low moods, lack of interest in hobbies.
Psychologists infer the hormone Melatonin plays a role in SAD, as the pineal gland
responds to lack of light and produces this.
Evaluation of Infradian rhythms:
Some further research suggests that menstrual cycles can be changed by exogenous zeitgebers.
Reinberg (1967) examined a woman who spent 3 months in a cave with one dim lamp as a light source. It
was noted that her menstrual cycle changed from her usual 28 days to 25.7 days, suggesting that the
lack of light affected her menstrual cycle, demonstrating the effect of exogenous zeitgebers on this
infradian rhythm. However, there is a chance that the change of time period was a confounding variable,
as the occurrence of menstrual cycles can fluctuate depending on stress, diet and amount of exercise.
Therefore, this could be supportive of the influence on infradian, perhaps further research is needed in
this field to be more credible.
There is research to suggest that infradian rhythms can impact regulation of behaviour. Penton -voak et
al. (psychologist into evolutionary psychology of facial attractiveness) found that woman preferred
feminised faces during the least fertile stage of their menstrual cycle and had a preference for a more
masculine face at their most fertile point. This suggests that infradian rhythm can motivate woman's
sexual behaviour.
Infradian rhythms: Take longer than 24 hours to complete its cycle.
The menstrual cycle: Controlled by monthly changes in hormones which regulates
ovulation, a complete cycle is every 24-36 days. 1, the lining of the womb sheds 2, during
end of the cycle Oestrogen levels heighten during each cycle causing development of an egg
which becomes ovulated. 3, following ovulation, womb lining thickens for pregnancy (If
pregnancy does not occur, egg is absorbed into the body and lining sheds)
Related study: Stern and Mcclintock (2005)
Can menstrual cycles synchronise in response to exogenous factors? Studied 29 women with
history of irregular periods. Samples of pheromones collected from 9 of the women at
different times of the menstrual cycle (cotton bud under armpit). These pheromones were
rubbed on the upper lip of the other participants.
Day One: given pads from first day of menstrual cycle Day Two: given pads from second day
of menstrual cycle etc.
Results: 68% of women experienced changes to their menstrual cycle which bought them
closer to the cycle of their 'odour donor'.
Seasonal Affective Disorder (SAD): A depressive disorder diagnosed in the DSM-5.
has a seasonal pattern of occurrence, believed to be caused by lack of daylight hours
during winter months (winter blues). Causes low moods, lack of interest in hobbies.
Psychologists infer the hormone Melatonin plays a role in SAD, as the pineal gland
responds to lack of light and produces this.
Evaluation of Infradian rhythms:
Some further research suggests that menstrual cycles can be changed by exogenous zeitgebers.
Reinberg (1967) examined a woman who spent 3 months in a cave with one dim lamp as a light source. It
was noted that her menstrual cycle changed from her usual 28 days to 25.7 days, suggesting that the
lack of light affected her menstrual cycle, demonstrating the effect of exogenous zeitgebers on this
infradian rhythm. However, there is a chance that the change of time period was a confounding variable,
as the occurrence of menstrual cycles can fluctuate depending on stress, diet and amount of exercise.
Therefore, this could be supportive of the influence on infradian, perhaps further research is needed in
this field to be more credible.
There is research to suggest that infradian rhythms can impact regulation of behaviour. Penton -voak et
al. (psychologist into evolutionary psychology of facial attractiveness) found that woman preferred
feminised faces during the least fertile stage of their menstrual cycle and had a preference for a more
masculine face at their most fertile point. This suggests that infradian rhythm can motivate woman's
sexual behaviour.
