Infradian Rhythms Flashcards
what are examples of infradian rhythms?
menstrual cycle
seasonal affective disorder (SAD)
what happens to the body during the menstrual cycle?
rising levels of oestrogen cause the ovary to develop and release an egg
then, progesterone helps the womb lining to thicken, readying the body for pregnancy
if pregnancy does not occur, the egg is absorbed back into the body and the womb lining goes away and leaves the body (menstrual cycle)
what did Stern and McClintock (1998) study?
how exogenous zeitgebers synchronise menstrual cycles
what was the process of Stern and McClintock’s (1998) study?
studied 29 women with irregular periods
pheromones were taken from them at different stages in their cycles via a cotton pad worn underneath their armpit for 8 hours
the pads were cleaned with alcohol and later rubbed on the upper lip of other participants
what were the results of Stern and McClintock’s (1998) study ?
68% of women experienced changes to their cycle which brought them closer to the cycle of their ‘odour donor’
what is an example of a circannual yearly cycle?
sad
how may melatonin cause seasonal affective disorder?
during the night, the pineal gland secretes melatonin until dawn when there is an increase in light
during winter, the lack of light in the morning means that the secretion goes on for longer
this has a knock-on effect of the production of serotonin in the brain (low serotonin levels are linked to depressive symptoms)
what are the strengths of research into infradian rhythms?
research on the menstrual has evolutionary value - Schank (2004)
research into SAD has practical applications - Eastman et al (1998)
what did Schank (2004) question?
it may have been advantageous for our female ancestors to menstruate together and become pregnant at the same time so offspring can be cared for collectively, increasing chance of survival
Schank (2004) questions the validity of this, as this produces competition for the highest quality males, lowering the fitness of potential offspring
what did Eastman et al (1998) find?
found phototherapy (a light box that stimulates very strong light in the morning and evening, thought to reset melatonin levels) relieves symptoms in up to 60% of sufferers
but the same study recoded a placebo effect of 30% using a ‘sham negative-ion generator’ - doubts the real value of phototherapy
what are the weaknesses of research into infradian rhythms?
methodology in menstruation synchronisation studies - different factors may affect the cycle
use of animals - the role of pheromones in animal sexual behaviour is well-documented and the basis of most of our knowledge, the role of pheromones in humans is speculative and inconclusive
