Research into circadian rhythms

Circadian rhythms: a type of biological rhythm based on a 24 hour cycle which regulates a number of body processes, for example, the sleep-wake cycle and changes in body temperature

Michael Siffre's cave study (1962)

• Hid in a dark cave for two months with no clock or reference to time
• Siffre's sleep-wake cycle settled to one that was around 25 hours and he fell asleep and woke up on a regular schedule
• Conclusion: even without natural light, our sleep-wake cycle is…