Circadian fluctuations in glucocorticoid level predict perceptual discrimination sensitivity

Summary Slow neurobiological rhythms, such as the circadian secretion of glucocorticoid (GC) hormones, modulate a wide variety of body functions. Whether and how such endocrine fluctuations also exert an influence on perceptual abilities is largely uncharted. Here, we show that phasic, moderate increases in GC availability prove beneficial to auditory discrimination. In an age-varying sample of N = 68 healthy human participants, we characterise the covariation of saliva cortisol with perceptual sensitivity in an auditory pitch-discrimination task at five time points across the sleep--wake cycle. First, momentary saliva cortisol levels were captured well by the time relative to wake-up and overall sleep duration. Second, within individuals, higher cortisol level just prior to behavioural testing predicted better pitch discrimination ability, expressed as a steepened psychometric curve. This effect of glucocorticoids held under a set of statistical control models. Our results pave the way for more in-depth studies on neuroendocrinological determinants of sensory encoding and perception.