What change in sleep/wake cycle was observed in a study by Siffre after spending 3 months in a cave?

• A. Adjusted to 22-24 hours
• B. Adjusted to 25-30 hours
• C. Adjusted to 27-29 hours
• D. No significant adjustment

Answer: (B)

In the study conducted by Michel Siffre, after spending three months in a cave, a noticeable change in the sleep/wake cycle was observed where participants adjusted to a rhythm that ranged from approximately 25 to 30 hours. This adjustment indicated that in the absence of external cues like natural light and societal time signals, the body's internal biological clock, or circadian rhythm, lengthened beyond the typical 24-hour cycle that is commonly associated with humans.

Siffre's findings highlight the flexibility of our biological rhythms and how environmental factors can influence our sleep patterns. The increase in cycle length suggests that our internal clocks are not strictly tied to the day-night cycle, but can adapt and shift significantly when those cues are removed. Understanding this phenomenon is crucial in the field of biological psychology as it informs us about how external environments and lack of sensory stimuli can affect our physiological processes, including sleep.