Infradian rhythms Flashcards
What are infradian rhythms?
A type of biological rhythm with a frequency of less than one cycle in 24 hours
What are two examples of infradian rhythms?
Menstural cycle
Seasonal affective disorder (SAD)
What is the menstural cycle governed by?
Monthly changes in hormone levels which regulate ovulation
How long is a menstural cycle?
Typically 28 days but can be anywhere between 24 and 35 days
Outline Stern and McClintock (1989)
Took pheromone samples from 9 women at different stages of their menstural cycle via swabs left in the armpit for 8 hours. These swabs were then rubbed on the top lip of a sample of 2 women with irregular periods over the course of a month. It was found that 68% of the sample experienced changes to their cycle which brought them into ‘sync’ with their ‘odour donor’
What is the value of menstural synchrony?
Evolutionary value - for our ancestors it may have been advantageous for females to mensturate together and therefore fall pregnant around the same time as newborns could be cared for collectively within the social group, increasing the offspring’s chance of survival
What does Schank (2004) argue about menstural synchrony?
Argued that the evolutionary perspective may lack validity. He argues that if there were too many females cycling together within a social circle, this would produce competition for the highest quality males and thereby lowering the fitness of any potential offspring.
Therefore, the avoidance of synchrony would appear to be more adaptive from an evolutionary perspective
Evaluate stern and McClintock (extraneous variables)
Criticised as it has been argued that there are many factors which may affect the menstural cycle including stress, changes to diet etc, all of which may act as confounding variables.
What is seasonal affective disorder (SAD) characterised by?
Persistent low mood and a general lack of interest in activities. It is also referred to as ‘winter blues’ as symptoms are triggered during the winter months when daylight hours are shorter
How is melatonin implicated in SAD?
As during the night the pineal gland secretes melatonin until dawn, lack of light in the morning means melatonin secretion continues for longer which is thought to have a knock on effect on serotonin production
What is the treatment used for SAD? What are the findings from this?
Psychotherapy - a lightbox which stimulates very strong light in the morning and evening and is thought to reset melatonin levels in sufferers of SAD
Eastman et al (1998) found that this treatment relieves symptoms in up to 60% of sufferers. However, the same study recorded an improvement in 30% of the sample using a placebo.
