Biological Rhythms: Infradian Rhythms

Question 1

What is an infradian rhythm?

Answer 1

A type of biological rhythm with a frequency of less than one cycle in 24 hours

e.g. menstration

Question 2

What is the menstural cycle?

Answer 2

• Governed by monthly changes in hormone levels which regulate ovulation
• Takes approx 28 days to complete
• During each cycle rising levels of the hormone oestrogen cause the ovary to develop an egg & release it (ovulation)
• After ovulation progesterone helps womb lining to grow thicker readying womb for pregnancy
• If pregnancy doesnt occur egg is absorbed into body

Question 3

What was the research conducted on synchonising the menstural cycle?

Answer 3

Stern & McClintok:
- Studied 29 women with a history of irregular periods
- Samples of phermones were gathered from 9 of women at different stages in their mentural cycle via a cotton pad placed under their armpit
- Pads worn for at least 8 hours to make sure phermones were picked up
- Pads were treated w alchol & frozen to be rubbed on the upper lip of other ppts

Question 4

What did Stern and McClintock find?

Answer 4

• On day one pads from start of menstural cycle were applied to all 20 women
• On day 2 they were given a pad from the second day of the cycle & so on

S&M found that 68% of women experienced changes to their cycle which brought them closer to the cycle of their ‘odour donor’

Question 5

How is SAD (seasonal affective disorder an infradian rhythm?)

Answer 5

• Particular type of infradium rhythm called a circannual rhythm as it is subject to a yearly cycle

Question 6

How have psychologists hypthesised that melatonin is linked to SAD?

Answer 6

• During the night the pineal gland secretes melatonin until dawn where there is an increase in light
• During winter the lack of light in the morning means this secretion process continues for longer
• This is thought to have a knock on affect on production of serotonin in the brain

Question 7

What is one strength of menstural synchrony research?

Answer 7

It may be explained by natural selection
Thought by some to have evolutionary value

• For our distant ancestors it may have been advntageous for females to menstrate together & become pregnant at same time
• So babies who had lost their mother during/after birth could have access to milk

Suggesting that synchronisation is an adaptive strategy

Question 8

What is one limitation of synchronisation studies?

Answer 8

• Their methodological short comings
  Many factors affecting a womens menstural cycle- stress,diet,exercise etc
  These may act as confounding variables meaning any supposed pattern of synchronisation is no more than would have been expected to occur by chance

Suggesting menstural synchrony studies are flawed