Biopsychology: Infradian Rhythms

Question 1

What Is An Infradian Rhythm?

Answer 1

• Any biological cycle that lasts longer than 24 hours.

Question 2

The Menstrual Cycle.

Answer 2

• Monthly rhythms.
• Refers to the day when the women is on her period to the day before her next.
• Cycle can last 23-36 days but most common is 28 days.
• During each cycle there is a rise in oestrogen causing the ovary to develop an egg and release it (ovulation) accompanied with oestrogen peak of 16-32 hours.
• After ovulation, progesterone levels are increased and helps womb lining grow thick in case of pregnancy.
• If pregnancy does not occur the egg is absorbed into the body and lining leaves body through period.

Question 3

Stern And McClintock’s Research.

Answer 3

Aim: Investigated whether menstrual cycles synchronises as a result of the influence of female pheromones.

Procedure: 29 women with irregular period were used. Samples of pheromones were taken from 9 women at different stages of their menstrual cycle, via cotton pad placed in their armpit. The pads were worn for at least 8 hours. The pads were then treated with alcohol and frozen. On day one pads from the start of the menstrual cycle were applied to the upper lip of 20 women. On day two they were given a pad from the second day of the cycle and so on.

Findings: 68% of women experienced changes to their cycle which brought them closer to the cycle of the order donor.

Conclusion: Menstrual cycles synchronise as a result of the influence of female pheroomones.

Question 4

Seasonal Affective Disorder (SAD).

Answer 4

• SAD is a depressive disorder which has a seasonal pattern.
• Main symptoms are low mood and general lack of activity and interest in life.
• Often referred to as the winter blues as they are triggered during the winter months when number of daylight hours becomes shorter.
• SAD is a particular type of infradian rhythm called a circannual rhythm as it is a yearly cycle.
• Melatonin is believed to cause SAD as due to the lack of light the pineal gland secretes melatonin for longer which has an effect on the produce of serotonin which has been linked to depressive symptoms.

Question 5

Illness And Deaths.

Answer 5

• In humans the calendar year influences behaviour regardless of the changes in temperature.
• The winter is associated with an increase in heart attacks, which varies seasonally and peaks in winter.
• There is an increase in annual deaths occurring in January.

Question 6

Infradian Rhythms Evaluation: Speculation Of Synchrony (CW).

Answer 6

• It may have been an advantageous for our female ancestors to menstruate together and become pregnant at the same time.
• This would have meant that offspring could be cared for collectively within a social group, increasing the offspring’s chance of survival.
• This would have been an evolutionary advantage.
• However, Schank questions the validity of the evolutionary perspective.
• Too many females cycling together within a social group would produce competition for highest quality males because the females would want the best potential genes for their offspring.
• Competition would likely lower the genetic fitness of potential offspring as the highest quality males are already taken.
• From this pov, avoidance of synchrony may be adaptive evolutionary strategy therefore the one that is naturally selected.

Question 7

Infradian Rhythms Evaluation: Weakness - Menstrual Cycle Confounding Variables.

Answer 7

• Critics argue that there are many factors that may change a woman’s menstrual cycle and act as a confounding variable.
• For example, stress and change in diet.
• This means that any supposed pattern of synchronisation as seen as McClintock’s study may have happened by chance.
• This suggests that important aspects of synchronisation studies may lack validity.

Question 8

Infradian Rhythms Evaluation: Strength - SAD Practical Applications.

Answer 8

• Research into SADs has practical application.
• An effective treatment for SAD is phototherapy, a lightbox that stimulates strong light in the morning and evening,
• It is thought to work by resetting the melatonin levels.
• This relieves symptoms in up to 60% suffers.
• This shows that research into infradian rhythms is beneficial as it helps improve the quality of peoples lives.

Question 9

Infradian Rhythms Evaluation: Weakness - Menstrual Cycle Speculative And Inconclusive.

Answer 9

• The role of pheromones in human behaviour is speculative and inconclusive.
• In Stern and McClintock’s study pheromones were taken from armpits of odour donors and given to participants.
• This is not reflective in how pheromones work in the real world.
• This questions the validity of the study and further questions the true role of pheromones in human behaviour.