Photoentrainment as Bayesian Inference: How the central circadian clock may weight and integrate the intensity and wavelength of natural light to estimate astronomical time

A Bayesian model for the mammalian central circadian clock shows how it can infer astronomical time from natural light by weighting intensity and spectral composition using prediction errors and relative uncertainty.

• Why it matters: Natural light varies with weather and seasons, so any single light value is an uncertain cue for time of day, yet the central clock stays closely aligned with astronomical time.
• What they did: The authors built a Bayesian inference framework that predicts the probability of observing light features given time of day, then updates clock phase via a weighted average of internal prediction versus observed light reliability.
• The result: Using one week of measurements from 59 human observers and 100 days of environmental spectra, the model characterizes daily light variability and explains the canonical phase response curve shape and integration of light properties by reliability.

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