infradian and ultradian rhythms

Question 1

infradian rhythm

Answer 1

a type of biological rhythm with a frequency of less than one cycle in 24 hours
e.g. menstrual cycle

Question 2

ultradian rhythm

Answer 2

a type of biological rhythm with a frequency of more than one cycle in 24 hours
e.g. the stages of sleep

Question 3

infradian rhythm research study
McClintock

Answer 3

• demonstrated how menstrual cycles may synchronise as a result of the influence of female pheromones
• 29 women with a history of irregular periods
• samples of pheromones were gathered from 9 women at different stages in their cycle via a cotton pad placed in their armpit for 8 hours
• the pads were treated with alcohol and frozen to be placed on the upper lip of other pps
• on day 1, pads from the start of the menstrual cycle were applied to all 20 women, on day 2 they were all given a pad from day 2 of the cycle and so on

Question 4

findings of McClintock’s study

Answer 4

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

Question 5

seasonal affective disorder (SAD) as an infradian rhythm

Answer 5

• a depressive disorder which has a seasonal pattern of onset
• symptoms are triggered during the winter months when the number of daylight hours become shorter
• psychologists have hypothesised that the hormone melatonin is implicated in the cause of SAD
• 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 results in a slower release of melatonin which has a knock-on effect on the production of serotonin

Question 6

stages of sleep

Answer 6

• psychologists have identified 5 distinct stages of sleep that altogether span 90 minutes and repeats throughout the night
  stages 1 and 2 - light sleep where the person may easily be woken and brainwave patterns become slower as sleep goes on
  stages 3 and 4 - involves delta waves which are slower and this is known as ‘deep sleep’
  stage 5 - REM (Rapid Eye Movement) sleep in which the body is paralysed but brainwaves are reflective of an awake brain, the stage associated with dreaming

Question 7

evaluation: evolutionary basis of the menstrual cycle

Answer 7

• menstrual synchrony is thought to have evolutionary value
• this is because it may have been advantageous for our ancestors to menstruate together so that they could fall pregnant at the same time
• this would result in the raising of babies as a group, improving their chances of survival

Question 8

evaluation: methodological implications in synchronisation studies

Answer 8

• commentators argue that there are many factors, such as confounding variables, that can change a woman’s menstrual cycle
• this means that any supposed synchronisation, as seen in the study by McClintock, is no more than a synchronisation that would have occurred by chance
• this reduces the validity of the research

Question 9

evaluation: evidence supports the idea of the stages of sleep

Answer 9

• brainwave activity was recorded on an EEG and the researchers controlled for the effects of caffeine and alcohol
• REM activity during sleep was highly correlated with dreaming, brain activity varied according to how vivid the dreams were, and those woken during dreams had very accurate recall
• this study shows that REM sleep is an important component of the ultradian sleep cycle