Exogenous Zeitgebers AO3

• -Different environments- exogenous zeitgebers don’t have the same effect on people who live in places where there is very little darkness in summer and very little light in winter. The Innuit Indians of the Arctic Circle have similar sleep patterns all year round, despite spending almost 6 months in total darkness. This suggests the s/w cycle is primarily controlled by endogenous pacemakers that can override environmental changes in light.
• -Miles reported the case of a man, blind from birth, with an abnormal circadian rhythm of 24.9 hours. Despite exposure to social cues - meal times- his s/w cycle couldn’t be adjusted. This suggests social cues alone aren‘t effective in resetting the biological rhythm and the natural body clock is stronger.
• +-Duffy found that natural changes in circadian rhythms mean older people fall asleep earlier and have poorer quality sleep. However Hood found that management of insomnia improved if elderly people were more active and had more exposure to natural light during the day. This suggests that exogenous changes in lifestyle may be just as likely to cause age related insomnia as internal, biologial changes.