Biological rhythms: Infradian rhythms

Question 1

Infradian rhythm

Answer 1

more than 24 hours periodicity- longer than a day
* e.g. the menstural cycle and seasonal affective disorder

Question 2

Research into the menstural cycle

Answer 2

Stern and McClintock
* 1998
* menstural cycle is an endogenous system, but theres evidence to suggest it may be influenced by exogenous factors - the cycles of other women
* 29 women with irregular periods
* samples of of pheromones gathered from 9 of the women at different stages of menstural cycles, via a cotton pad placed under the armpit for at least 8 hours
* pads then treated with alcohol and frozen to be rubbed on upper lip of other participants
* day 1- pads from start of menstural cycle were applied to all women
* day 2- ppts were all given a pad from the second day of the cycle
* found that 68% of women experienced changes in their cycle which brought them closer to the cycle of the ‘odour donor’
* this implies that it is possible to influence the menstural cycle through exogenous factors

Question 3

Evaluation

Answer 3

• confounding variables
• self report methods
• low in population validity
• critiques from other studies
  + evolutionary research

Question 4

Confounding variables

Answer 4

stress, changes in diet etc, are extraneous variables
this means that any supposed patterns of synchronisation may have occured by chance

Question 5

• Self report methods

Answer 5

relies on ppts to self report the onset of their menstural cycle. this leads to demand characteristics and social desirability bias

Question 6

• Low in population validity

Answer 6

study used 29 ppts which means its a small sample size

Question 7

• critiques from other studies

Answer 7

other studies failed to find similar results (e.g. Travathan et al). much of knowledge of the influence of pheromones on behaviour is derived from animal studies

Question 8

+ Evolutionary research

Answer 8

synchronization could have an evolutionary advantage- women having menstural periods are more likely to have children together and collectively care

Question 9

SAD

Answer 9

Seasonal affective disorder
* depressive disorder, diagnosed as a mental disorder by DSM - 5
* winter blues (symptoms develop in winter season= infradian rhythm )
* its a particular infradian rhythm known as a circannual rhythm as its subject to a yearly cycle
* melatonin has been implicated with SAD
* during night penal gland secretes melatonin
* during winter this occurs for a longer period as there is less daylight
* melatonin reduces brain activity and decreases the amount of serotonin in the brain, affecting mood

Question 10

Research into SAD

Answer 10

• one of the most effective treatments of SAD is phototherapy
• this stimulates very strong light in the mornings and evenings and is though to reset melatonin levels
  Eastman (1988) found that phototherapy relieves symptoms in up to 60% of sufferers

Question 11

Evaluation

Answer 11

• Placebo effect

Question 12

• Placebo effect

Answer 12

the same study recorded a placebo effect in 30% of ppts using a different form of treatment. the placebo affect is when the ppts are given a different form of treatment but are told that its phototherapy. this is a problem because it casts doubts on the chemical influence of phototherapy