Sleep studies show that a percentage of humans have an intrinsic biological clock of 28 hours or greater
the verdict
REFUTED
the evidence says no
confidence 14/100
Sleep studies consistently show that the human intrinsic biological clock has a free-running period very close to 24 hours, contradicting the claim that a percentage of humans possess an intrinsic clock of 28 hours or greater.
Evidence against · 3
Intrinsic near-24-h pacemaker period determines limits of circadian entrainment to a weak synchronizer in humans
2001 · cited by 216
Czeisler et al. (2001) demonstrated that the average intrinsic circadian period of the human biological clock is extremely close to 24 hours (specifically, very near a 24-h day).
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More against · 2
Circadian rhythm phase shifts and endogenous free-running circadian period differ between African-Americans and European-Americans
2015 · cited by 92
Duffy et al. (2015) found that human free-running circadian periods differ slightly among populations (such as European-Americans and African-Americans), but remain tightly clustered around 24 hours rather than reaching 28 hours.
Mathematical analysis of light-sensitivity related challenges in assessment of the intrinsic period of the human circadian pacemaker
2023 · cited by 0
Sthapit et al. (2023) noted that even among free-running blind individuals—who exhibit some of the longest measured intrinsic periods—the mean period is approximately 24.50 hours, well below 28 hours.