Biopsychology : Infradian Rhythms Flashcards
What is an infradian rhythm?
nfrequent – biological rhythm controlled by a cycle which lasts more than one day. E.g, menstrual cycle, SAD
Describe the sequence of the menstrual cycle
Governed by monthly changes in hormonal levels that regulate ovulation. Rising levels of oestrogen cause the ovary to develop and releases egg. Progesterone helps womb lining grow thicker to prep for implantation of embryo. If no pregnancy, egg is absorbed into body and womb lining comes away and leaves body (menstrual flow).
McClintock & Stern (1998) study - Aim
to investigate whether the menstrual cycle is influenced by pheromones from other women
McClintock & Stern (1998) study - Procedure
29 female uni students not on birth control at diff stages of their period. Samples of pheromones gathered from 9 women via a cotton pad under their armpit (for 8hrs). The other 20 participants exposed to the pheromones and their menstrual cycles were monitored.
McClintock & Stern (1998) study - Findings
when the experimental group inhaled secretions from women about to ovulate, their cycles became shorter. When they inhaled secretions from women who’d just ovulated, their cycles became longer. McClintock found that
68% of women experienced changes to their cycle.
McClintock & Stern (1998) study - Conclusion
the experimental groups cycles were affected by the secretions from control group. This explains why when a group of women live in close proximity, their cycles tend to synchronise. Their infradian rhythms were affected by external (exogenous) factors.
Seasonal Affective Disorder - What is it?
SAD is a depressive disorder w a seasonal pattern onset, described and diagnosed as a mental disorder in DSM-5. Same as other forms of depression, you have a persistent low mood alongside general lack of activity and interest in life. ‘Winter blues’ – triggered during winter months when daylight becomes shorter.
Seasonal Affective Disorder - What type of infradian rhythm is it?
Circannual – subject to yearly cycle. During the night the pineal gland secrets melatonin which has a knock on effect to serotonin (happy chemical) and since there’s more darkness during winter.
Seasonal Affective Disorder - How do you treat it?
Light therapy – exposure to bright artificial light mimicking sunlight, helping to reset circadian rhythms. It increases serotonin by reducing melatonin.
Strengths of infradian rhythms…
• Supporting evidence that the menstrual cycle is influenced by exogenous zeitgebers → Reinberg (1967) reported on a woman who spent three months isolated in a cave with minimal light (only a small lamp). During this period, her menstrual cycle shortened from the typical 28 days to 25.7 days. But, lack of control of EVs plus only 1 case study.
• Evidence that EZs play a role in sexual preference → Penton-Volk et al. (1999) conducted research showing that women preferred feminine male faces during the least fertile stage of their menstrual cycle, and more masculine faces.
Limitations of infradian rhythms…
• Lack of rigorous control → While the research attempted to demonstrate exogenous influences on biological rhythms, it didn’t account for a variety of factors that could affect the timing of a woman’s period (stress, dietary changes, physical activity, environmental factors – light exposure.)
• Contrary evidence from evolutionary theory → assumes synchrony has adaptive value by enabling collective childcare and increasing offspring survival. However, it’s challenged by Schank (2004), who argued that if too many women cycle together, it could lead to increased competition for the most desirable males.
• Contrary evidence that EZs affect SAD → While phototherapy (lightbox to simulate strong light in morning and evening), is an effective treatment for many, with Eastman et al. (1998) reporting a 60% relief in symptoms, the same study also found a 30% placebo effect using a fake generator.
• SAD therapy has short term solutions → Sanassi (2014) found that light therapy reduced symptoms in 80% of people, but Rohan et al. (2009) recorded a relapse rate of 46% over next winters, compared to only 27% in a comparison group receiving CBT.
Limitations of infradian rhythms…
• Lack of rigorous control → While the research attempted to demonstrate exogenous influences on biological rhythms, it didn’t account for a variety of factors that could affect the timing of a woman’s period (stress, dietary changes, physical activity, environmental factors – light exposure.)
• Contrary evidence from evolutionary theory → assumes synchrony has adaptive value by enabling collective childcare and increasing offspring survival. However, it’s challenged by Schank (2004), who argued that if too many women cycle together, it could lead to increased competition for the most desirable males.
• Contrary evidence that EZs affect SAD → While phototherapy (lightbox to simulate strong light in morning and evening), is an effective treatment for many, with Eastman et al. (1998) reporting a 60% relief in symptoms, the same study also found a 30% placebo effect using a fake generator.
• SAD therapy has short term solutions → Sanassi (2014) found that light therapy reduced symptoms in 80% of people, but Rohan et al. (2009) recorded a relapse rate of 46% over next winters, compared to only 27% in a comparison group receiving CBT.
