Pupil-linked arousal does not differ between white, pink and brown noises

Coloured noises, such as white, pink, and brown noise, have gained attention in popular media as potential tools for enhancing memory consolidation, sleep quality, attentional focus, and more. These terms refer to distinct spectral slopes, which give rise to perceptually different noise stimuli. Although empirical research on their effects remains limited, a prevailing hypothesis suggests that their influence may be mediated by differential effects on arousal. In this study, we investigated this hypothesis using pupillometry, a physiological marker closely linked to arousal. Participants (N = 31) listened to three types of noise (white, pink, and brown), each presented for 10 sec, while their pupil diameter was recorded. The results showed no significant modulation of pupil size across noise conditions. These findings suggest that, despite widespread claims about the distinct arousing or calming properties of coloured noises, they do not differentially affect sustained pupil-linked arousal.