Biological rhythms- exogenous zeitgebers Flashcards
If the point is:
A strength of exogenous zeitgebers is that there’s evidence to support their role in regulating circadian rhythms like the sleep/ wake cycle.
What is the evidence and link?
Evidence- Vetter et al investigated the effect of changing light temperature at the workplace from 4000K to 8000K on the sleep/wake cycle and activity rest behaviour. The experimental group that experienced the light change was compared with a non intervention group that remained in the 4000K environment throughout the 5 week study period. Sleep logs continuously assessed sleep/wake behaviour and activity patterns. The results suggested that artificial blue enriched light competes with natural light as a zeitgeber. The subjects working under the warmer 4000K light synchronised to a natural dawn and the subjects exposed to blue enriched 8000K light synchronised to office hours.
Link- This supports the idea that light is the dominant zeitgeber in the human sleep/ wake cycle.
If the point is:
A weakness of exogenous zeitgebers is that many of the studies are conducted in lab environments with artificial tasks.
What is the evidence and link?
Evidence- For example, in Vetter’s study, it is unrealistic that no one was exposed to any blue light, giving the study low ecological validity.
Link- Therefore, this research may not provide credible evidence for the role of exogenous zeitgebers in controlling circadian rhythms.
If the point is:
Another weakness of exogenous zeitgebers is that there is contradictory evidence about the role of light being one.
What is the evidence and link?
Evidence- For example, Luce and Segal suggested light levels can be overridden. In the arctic circle, people still maintain a reasonably constant sleep pattern, averaging 7 hours a night, despite 6 months of darkness in winter followed by 6 months of light in summer.
Link- This suggests that, in these conditions, it appears to be social factors that act to reset endogenous rhythms, rather than light levels.
If the point is:
Another weakness of exogenous zeitgebers is that individual differences need to be taken into account when exploring the role of exogenous zeitgebers in regulating circadian rhythms, as the role of these may be underestimated.
What is the evidence and link?
Evidence- Such as the number of hours a person naturally sleeps at night.
Link- This means the role of exogenous zeitgebers isn’t straight forward, as variables like age, lifestyle, personality and even culture can have a significant effect on circadian rhythms.
What are exogenous zeitgebers?
External stimuli from the environment which provide information about elapsed time and prompt changes in bodily activity and the patterns of our biological rhythms
What are the evaluations for exogenous zeitgebers?
+ There’s evidence to support their role in regulating circadian rhythms like the sleep/ wake cycle
— Many of the case studies are conducted in lab environments with artificial tasks
— There is contradictory evidence about the role of light being an exogenous zeitgeber
— Individual differences need to be taken into account when exploring the role of exogenous zeitgebers in regulating circadian rhythms, as the role of these may be underestimated
