In a study, a blind individual had a sleep/wake cycle of how many hours?

• A. 24.0 hours
• B. 24.5 hours
• C. 24.9 hours
• D. 25.0 hours

Answer: (C)

The correct answer is based on research regarding the circadian rhythms of individuals who are blind. For many blind individuals who do not receive light cues that help regulate the circadian rhythm, their biological clock can shift and deviate from the standard 24-hour cycle. Studies have shown that some of these individuals exhibit sleep/wake cycles that can extend to approximately 24.9 hours. This subtly longer cycle reflects the inherent biological variations that occur in the absence of external light cues, which are critical for synchronizing the circadian rhythm to the environment.

This phenomenon highlights the interplay between biological processes and environmental factors, underlining the importance of visual cues in regulating sleep patterns for individuals with normal sight. The deviation in the sleep/wake cycle for blind individuals often leads to challenges in maintaining regular sleep patterns, but evidence indicates that an approximate 24.9-hour cycle is a common finding in such cases.