Biological Rhythms: Infradrian rhythms Flashcards
What are infradian rhythms?
Infradian rhythms are biological rhythms that last more than 24 hours/longer than a day
What were the findings of the research into the menstrual cycle being an infradian rhythm (endogenous system), being affected by exogenous factors (pheromones + pads)
Stern and McClintock found 68% of the women experienced changes in their cycle which brought them closer to the cycle of the “odour donor”. This study implies it is possible to influence the menstrual cycle through exogenous zeitgebers
Outline the research into the menstrual cycle being an infradian rhythm (endogenous system), being affected by exogenous factors (pheromones + pads)
Sterna and McClintock looked at 29 women with irregular periods. Samples of pheromones were gathered from 9 of the women at different stages of their menstrual cycles, through cotton pads placed under their armpits for 8 hours. These cotton pads were then placed on the upper lip of the other participants. On day one, pads from the start of the menstrual cycle were applied to all 20 women, on day 2 they were all given a pad from the second day of the cycle etc.
What are the limitations of research into the menstrual cycle being an infradian rhythm (endogenous system), being affected by exogenous factors (pheromones + pads)?
1. confounding variables
2. self report method
3. sample size
4. replicability
- There are a few confounding variables within the study. The woman could have been experiencing stress, changes in their diet etc. This could have meant that any supposed patterns of synchronization may have occurred by chance
- This experiment used a self report method, relying on the participant’s own report of their onset of menstrual cycle. This could result in inaccurate results
- This study had a small sample size of 29 women making any findings found less generalisable. Also resulting in a lack of population validity
- Other studies have failed to reproduce similar results. This is because much of the knowledge of the influence of pheromones on behaviour is derived from animal studies. As a result this study lacks external reliability
What is a strength of the research into the menstrual cycle being an infradian rhythm (endogenous system), being affected by exogenous factors (pheromones + pads). (evolutionary adavantage)
Sychronization could have an evolutionary advantage. This is because women having menstrual periods together are more likely to have children together and therefore share caring collectively
What is another example of infradian rhythms? (SAD)
Seasonal affective disorder
What is seasonal affective disorder (SAD)?
Seasonal affective disorder is a depressive disorder known as the winter blues
What type of biological rhythm is seasonal affective disorder?
Circannual rhythm
How long does a circannual rhythm cycle last for?
The circannual rhythms has a yearly cycle
What causes seasonal affective disorder?
The hormone melatonin has been implicated in seasonal affective disorder. At night, the penal gland secretes melatonin. During winter, this occurs for longer periods as there is less daylight . This causes higher levels of melatonin
What are the effects of melatonin on the brain?
Melatonin reduces brain activity and decreases the amount of serotonin in the brain, affecting moods
Outline the research study into seasonal affective disorder:
One of the most effective treatments for seasonal affective disorder is phototherapy. This treatment stimulates strong light in the morning and evenings, as a means of resetting melatonin levels
What is an evaluation of the research study into seasonal affective disorder?
The study recorded a placebo effect in 30% of participants using a different form of treatment. A placebo is when participants are given a different form of treatment but told it is the original treatment. This casts double on the chemical influence of phototherapy
