Biopsychology: Infradian rhythms

Question 1

What type of cycle does an Infradian rhythm have?

Answer 1

A cycle that lasts more than 24 hours

Question 2

What’s an example of an Infradian rhythm? and why would it be seen as an Infradian rhythm?

Answer 2

The menstrual cycle

• governed by monthly changes in hormone levels which regulate ovulation
• Occurs roughly every 28 days

Question 3

What type of system is the menstrual cycle?

Answer 3

An endogenous system

Question 4

What does evidence suggest about the menstrual cycle?
- what may it be influenced by (+ example)

Answer 4

It may be influenced by exogenous factors, such as the cycles of other women

Question 5

Who did a study on how menstrual cycles may synchronise as a result of the influence of pheromones?

Answer 5

Stern & McClintock

Question 6

Stern & McClintock
AIM:
METHOD:
RESULTS:

Answer 6

AIM: To see if menstrual cycles may synchronise as a result of the influence of pheromones

METHOD:
- 29 women with a history of irregular periods
- samples of pheromones gathered from 9 of the women at different stages of their cycle (cotton pad placed in armpit)
- pads worn for at least 8 hrs to ensure pheromones were picked up
- pads treated with alcohol & frozen, to be rubbed on upper lip of other participants

RESULTS:
- 68% of women experienced changes to their cycle
- which brought them closer to the cycle of their ‘odour donor’

Question 7

What’s another example of an Infradian rhythm? and what is it?

Answer 7

Seasonal affective disorder (SAD)

• depressive disorder which has a seasonal pattern of onset

Question 8

What is Seasonal affective disorder (SAD) described & diagnosed as by the DSM-5?

Answer 8

A mental disorder

Question 9

What are the main symptoms of Seasonal affective disorder (SAD)?

Answer 9

• persistent low mood
• general lack of activity & interest in life

Question 10

What are these symptoms triggered by?

Answer 10

The winter months when the number of daylight hours becomes shorter

Question 11

What 2 types of infradian rhythm can SAD be classed as and why?

Answer 11

A circannual rhythm - subjected to a yearly cycle

A circadian rhythm - the experience of SAD may be due to the disruption of the sleep/wake cycle

Question 12

What have psychologists hypothesised about the hormone melatonin?

Answer 12

That it is implicated in the cause of SAD

Question 13

Explain how melatonin works and why it might be linked to the cause of SAD?

Answer 13

1. During the night, the pineal gland secretes melatonin until dawn where there is an increase in light
2. During winter, the lack of light= secretion process continues for longer
3. Thought to have a knock-on-effect on the production of serotonin in the brain - a chemical that has been linked to the onset of depressive symptoms

Question 14

STRENGTH of menstrual cycle synchrony research

Answer 14

POINT: May be explained by natural selection

EVIDENCE:
- Synchronisation of the menstrual cycle (like in Stern & McClintock’s study) is thought to have evolutionary value.
- Distant ancestors - may have been advantageous for women to menstruate together and become pregnant at same time.

EXPLAIN:
- In a social group, would allow babies who has lost their mothers during or after childbirth to have access to breastmilk
- Improving their chances of survival

LINK: Suggests that synchronisation is an adaptive strategy

Question 15

LIMITATION of synchronisation studies

Answer 15

POINT: Methodological limitations

EVIDENCE:
- are many factors that may effect change to menstrual cycle (e.g. stress, changes in diet, exercise, etc)

EXPLAIN:
- These may act as confounding variables
- suggests why others have failed at replicating the findings (e.g. Trevathan et al)

LINK: Suggest that menstrual synchrony studies are flawed