Biological Rhythms

Question 1

Define a circadian rhythm with an example.

Answer 1

A bodily rhythm that lasts roughly 24 course. E.g. sleep-wake cycle.

Question 2

Define an ultradian rhythm and give an example.

Answer 2

A bodily rhythm that lasts less than 24 hours. E.g. stages of sleep cycle.

Question 3

Define an infradian rhythm and give an example.

Answer 3

A bodily rhythm that lasts longer than 24 hours e.g. Seasonal Affective Disorder or the Menstrual Cycle.

Question 4

Define and exogenous zeitgeber.

Answer 4

An external factor that influences the biological rhythm in question. E.g. light, temperature.

Question 5

Outline Siffre’s study.

Answer 5

He spent up to six months in a cave, when he came out, his circadian rhythm had been effected to such an extent that he thought it was a month earlier than it was.

Question 6

Give an advantage of the Circadian Rhythm.

Answer 6

Advantages:
- Supporting evidence - Aschoff and Wever - repeated Siffre’s study on a larger scale - pps demonstrated a circadian rhythm of 24 hours - exogenous zeitgebers do have an impact.

• Supporting evidence from Folkard - a clock in a cave was slowly sped up unbeknownst to participants resulting in them having a circadian rhythm of 22 hours - no pps could comfortably adjust - circadian rhythm may be effected by endogenous zeitgebers.

Question 7

Give a disadvantage of circadian rhythms.

Answer 7

• Circadian rhythms differ on an individual basis - Duffy et al - ‘morning people’ and ‘evening people’ - samples must consist of those of similar classification.
• Buhr et al - temperature may be more influential than light - more holistic approach to research may be required.
• Extraneous variables may confound the results - Czeisler found that artificial light can influence the circadian rhythm - Siffre’s use of light may invalidate the findings.

Question 8

Provide an advantage of infradian rhythms.

Answer 8

Advantages:
- Evidence supports the role of melatonin in SAD - Terman - countries in the northern hemisphere produce higher rates of SAD - 10% in New Hampshire - 2% in Florida.

• Supporting evidence for the role of exogenous zeitgebers - Reinberg - artificial light can influence the menstrual cycle, in his case, making it shorter.
• Further evidence supporting the role of exogenous zeitgebers - McClintock et al - pheromones of other females synchronised their menstrual cycles - though does not discredit other exogenous factors.

Question 9

Provide an advantage of Ultradian Rhythms.

Answer 9

Advantages:
- Supporting evidence of the sleep-wake cycle - Dement and Kleitman - positive correlation between brain activity and REM sleep - correlational - no causation.

• Evidence from case studies - Randy Gardener - stayed awake for 264 hours - only recovered 1/4 of the lost sleep - demonstrates the flexibility of ultradian rhythms.

Question 10

Provide a disadvantage of infradian rhythms.

Answer 10

Disadvantages:
- Methodological flaws in research into infradian rhythms - small sample of McClintock’s study - low population validity.

Question 11

Provide a disadvantage of ultradian rhythms.

Answer 11

Disadvantages:
- Differences in people make pattern studying difficult - Tucker et al - found significant differences in duration of stages 3 and 4 - caution must be taken when drawing conclusions from these studies.

• Artificial methodology - carried out in a controlled way where participants may have difficulty sleeping - low ecological validity.