To investigate what would happened to our natural sleep-wake cycle if we had no external cues from the environment such as daylight telling us what time it was. Siffre spent long periods of time underground to understand his own biological rhythms.
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Procedure 1
Siffre was a speleologist (cave expert) who investigated the natural duration of his own sleep-wake cycle. Siffre spent six months in a cave with only weak artificial light starting on - 14th February 1972
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Procedure 2
There was no natural light, so he didn't know what time it was, and he had no external cues to guide his rhythms - no daylight, clocks or radios.
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Procedure 3
He had contact with researchers via a telephone, and his psychological functions were measured, and behaviour observed throughout
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Procedure 4
Siffre had no clock or any reference to time; however, he did have verbal contact with the outside world. he would phone his team of researchers above ground to let them know he was awake and when he thought the day had begun.
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Procedure 5
He simply woke, ate and slept when he felt like it. The only influence on his behaviour was his 'internal clock'
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Procedure 6
His new temporary home was a large chamber in which there was a bed table and chair. He took frozen food and 780 gallons of water to sustain him whilst he carried out several experiments underground.
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Experiments included:
taking blood pressure, various memory and physical tests.
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Results 1
The findings were that his sleep-wake cycle settled naturally around 25 hours, although sometimes it would range up to 48 hours.
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Results 2
Siffre organised his day into a fairly normal pattern of alternating periods of sleep and activity, and his day was separated by his eating behaviours. However, his biological clock shifted to 25-hour-days.
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Results 3
The effects on Siffre himself were quite severe. He became depressed and longed for company to break the monotony and his loneliness. He thought about abandoning the project any times and even had suicidal thoughts.
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Conclusion 1
Siffre concluded that the absence of natural daylight allowed his biological clock to run at its natural rate, and that normally daylight acted as an exogenous zeitgeber to resynchronise the cycle
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Conclusion 2
Siffre (1975) found the absence of external cues significantly altered his circadian rhythm: when he returned he believed that the date was to be a month earlier that what it was (no external cues).
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Conclusion 3
This suggests that his 24-hour sleep-wake cycle increased by the lack of external cues. There is internal control of the circadian rhythm, since even in the absence of external cues we are able to maintain a regular daily cycle.
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Other cards in this set
Card 2
Front
Siffre was a speleologist (cave expert) who investigated the natural duration of his own sleep-wake cycle. Siffre spent six months in a cave with only weak artificial light starting on - 14th February 1972
Back
Procedure 1
Card 3
Front
There was no natural light, so he didn't know what time it was, and he had no external cues to guide his rhythms - no daylight, clocks or radios.
Back
Card 4
Front
He had contact with researchers via a telephone, and his psychological functions were measured, and behaviour observed throughout
Back
Card 5
Front
Siffre had no clock or any reference to time; however, he did have verbal contact with the outside world. he would phone his team of researchers above ground to let them know he was awake and when he thought the day had begun.
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