A03 - Ultradian & Infradian Rhythms

• Strength Infradian & Ultradian Rhythms - Menstrual Cycle

  P: One strength is research on the menstrual cycle shows its evolutionary basis.

  E: For our distincy ancestors it may have been advantageous for females to menstruate together and become pregnant at the same time.

  E: In a social group, this would allow babies who had lost their mothers to have access to breast milk, thereby improving their chances of survival.

  L: This suggests that synchronisation is an adaptive strategy.
• HOWEVER - Menstrual Cycle (Infradian & Ultradian Rhythms)

  P: There is conflict in views when trying to understand the adaptive need for synchronicity of menstrual cycle.

  E: Initially it seems adaptive, as it meant females in group fall pregnant at same time & newborns can be cared for collectively.

  E: BUT, Schank (2004) argues would lead to too much competition for best mate & lower the fitness/chances/success of offspring.

  L: This makes it difficult to see value of menstrual synchronicity from evolutionary perspective & alternative explanation needed to try to understand this phenomenon.
• Empirical Evidence for stages of sleep - (Infradian & Ultradian Rhythms)

  P: There is empirical evidence from EEG studies to support the existence of distinct stages of sleep.

  E: Dement & Kleitman (1957) monitored ppts sleep & found REM activity was highly correlated with the experience of dreaming.

  E: Additionally, brain activity varied depending on how vivid those dreams were.

  L: This shows accuracy of understanding of the REM stage of sleep where the body is paralysed yet brain activity speeds up, increasing the validity of the theory.
• Real world application - (I&U Rhythms) - PT 1

  P: One of most effective (& cheapest) ways of treating SAD is with phototherapy (REAL WORLD APPLICATION).

  E: Light therapy reduces debilitating effects of SAD (e.g. excessive sleepiness) in around 80% people (Sanassi 2014). It's safer than using antidepressants.

  E: Rohan et al. (2009) recorded relapse rate of 46% over successive winters, compared to 27% in comparison to groups receiving CBT.

  L: Suggests light therapy may be effective short-term treatment but additional treatments may be required if benefits are to be maintained.
• Real World Application & SAD - (Infradian & Ultradian Rhythms)

  - PART 2

  E: Eastman et al (1998) found symptoms were relieved in 60% of sufferers who looked at a light box in the morning and evening. Eastman et al (1998) found symptoms were relieved in 60% of sufferers who looked at a light box in the morning and evening. However, the same study found a 30% improvement in sufferers treated with a placebo.

  L: This questions the chemical influence of phototherapy and suggests SAD may be treated equally well using psychological techniques instead.
• Low External Validity - Infradian & Ultradian Rhythms- PART 1

  P: EEGs are primary source of data collection in this area.

  E: This good in sense EEGs provide objective data & all participants measured in lab in same way thus increasing reliability & validity of results.

  E: Sleep measured in lab, one of benefits of lab settings is control of extraneous variables, like noise/temperature that affect sleep. BUT, ppt's awareness of situation may affect their sleeping patterns affecting validity of results.
• Low External Validity - Infradian & Ultradian Rhythms- PART 2

  E: Also, lab studies involve ppt being attached to complicated machinery, so their sleep doesn't represent ordinary patterns.

  L: So until there is more natural way of collecting data, caution must shown when analysing EEG data. This dilemma means might be best to conduct some studies in people’s own homes and compare patterns with records made in lab settings.
• Chance limitation of Infradian & Ultradian Rhythms

  P: One limitation is the methodology used in synchronisation studies:

  E: There are many factors that may change a woman's menstrual cycle and act as confounding variables (e.g. stress, changes in diet, etc).

  E: Any supposed pattern may occur by chance. This may be why other studies (e.g. Trevathan et al 1993) have not replicated Stern and McClintock’s original findings.

  L: This suggests that menstrual synchrony studies are flawed.
• Individual Differences/methodological issues limitation - Infradian & Ultradian Rhythms

  P: One limitation is individual differences in sleep stages:

  E: Tucker et al (2007) found large differences between participants in the duration of stages 3 and 4.

  E: They suggest that these differences are biologically determined.

  L: This makes it difficult to describe ‘normal sleep’ in any meaningful way.
• Practical Value of Ultradian Rhythms - strength of Infradian & Ultradian Rhythms

  P: One strength is understanding age-related changes in sleep.

  E: SWS reduces with age. Growth hormone is produced during SWS so this becomes deficient in older people.

  E: Van Cauter et al (2000) suggest the reduced sleep may explain impairments in old age. SWS sleep can be improved using relaxation and medication.

  L: This suggests that knowledge of ultradian rhythms has practical value.
• A03 - Infradian & Ultradian Rhythms

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• A03 EVALUATION - Infradian & Ultradian Rhythms


  EVALUATION:

  + Practical Value of Ultradian Rhythms

  -Individual Differences/methodological Issues

  -Chance

  -Low External Validity

  +Real World Application

  +Empirical Evidence for stages of Sleep

  +Menstrual Cycle

  -HOWEVER (menstrual cycle)