Infradian Rhythms

Question 1

What is an infradian rhythm?

Answer 1

Rhythms that have a duration of over 24 hours

Question 2

Give an example of a monthly rhythm

Answer 2

• The menstrual cycle takes about 28 days.
• The cycle is regulated by hormones, rising levels of oestrogen causes the ovary to develop and release an egg (ovulation)
• Progesterone thickens womb lining
• If pregnancy doesn’t occur, egg is observed and womb lining sheds

Question 3

Give an example of an annual rhythm

Answer 3

• SAD (Seasonal Affective Disorder) is a depressive disorder with seasonal patterns. Symptoms triggered during winter when daylight hours are shorter
• SAD may be caused by melatonin, the pineal gland secretes melatonin until dawn, during winter, the lack of light in the morning means secretion goes on for longer
• Indirect effects of less serotonin the brain (depressive symptoms)

Question 4

Give a study of a monthly rhythm

Answer 4

• Studied 29 women with irregular period
• Pheremones taken from some at different stages of their cycle via a cotton pad under their armpits. Cotton pads cleaning with alcohol then rubbed on the upper lips of other participants
• 68% of the women’s cycles got closer to that of their ‘odour donor’
• Menstrual cycles may synchronise due to the influence of female pheremones

Question 5

Give evaluation for infradian rhythms (evolutionary basis)

Answer 5

• A strength of menstrual synchrony research is that it can be explained by natural selection
• Synchronisation of the menstrual cycle, as observed in the Stern and McClintock study, may have some evolutionary value. It may have been advantageous for women to menstruate together and become pregnant at the same time. This would allow babies who lost their mother at childbirth to access milk, and improving their chances of survival.
• Supports the synchronicity of the menstrual cycle

Question 6

Give evaluation for infradian rhythms (methodological limits)

Answer 6

• A limitation of synchronisation studies is they may have been subject to confounding variables
• e.g. There are many exogenous factors that may affect the menstrual cycle, including stress, diet and exercise. These confounding variables, which means that any supposed pattern of synchronisation is no more than what would’ve neem expected to occur by chance. Similarly, the study relied on women accurately reporting the onset and duration of their cycles.
• This suggests that McClintock’s findings only occurred by change and the result is not useful and invalid

Question 7

Give evaluation for infradian rhythms (real-world application)

Answer 7

• Research into SAD has produced great practical application for sufferers
• e.g. Light therapy work by simulating a very strong light, in the morning and the evening. It resets melatonin and relieves symptoms in up to 60% of sufferers found by Eastman
• This a major strength as understanding the role of melatonin has helped to produced therapies to aid SAD patients
• However, light therapy can produce headaches and eyes strain, which can lead to people relapsing, therefore reducing its successfulness