The significance of the role on endogenous pacemakers is revealed by the case study of MICHEL SIFFRE. SIFFRE, a French geologist, decided to investigate what would happen if all Zeitgebers were removed. He spent 7 months underground in a cave where no natural light or sound could reach him. He had food, drink, could exercise, and was in contact with the outside world via a telephone. He had no means of knowing what time it was. It was found that Siffre’s physiology and behaviour remained cyclical but his day was extended to 25 hours rather than 24 hours.
The findings of this research are based on a case study involving a single individual and it might be argued that we cannot make generalisations from a single case study to the general population as it fails to reflect individual differences. However, case studies can be insightful and in fact, the study by SIFFRE suggests that our natural rhythm is 25 hours and this is confirmed by the case history of a young adult male, blind from birth, who had a 24.9 hours circadian rhythm (MILES).
