Neural basis of melodic learning explains cross-cultural regularities in musical scales

SummarySeeking exposure to unfamiliar experiences constitutes an essential aspect of the human condition, and the brain must adapt to the constantly changing environment by learning the evolving statistical patterns emerging from it. Cultures are shaped by norms and conventions and therefore novel exposure to an unfamiliar culture induces a type of learning that is often described as implicit: when exposed to a set of stimuli constrained by unspoken rules, cognitive systems must rapidly build a mental representation of the underlying grammar. Music offers a unique opportunity to investigate this implicit statistical learning, as sequences of tones forming melodies exhibit structural properties learned by listeners during short- and long-term exposure. Understanding which specific structural properties of music enhance learning in naturalistic learning conditions reveals hard-wired properties of cognitive systems while elucidating the prevalence of these features across cultural variations. Here we provide behavioral and neural evidence that the prevalence of non-uniform musical scales may be explained by their facilitating effects on melodic learning. In this study, melodies were generated using an artificial grammar with either a uniform (rare) or non-uniform (prevalent) scale. After a short exposure phase, listeners had to detect ungrammatical new melodies while their EEG responses were recorded. Listeners performance on the task suggested that the extent of statistical learning during music listening depended on the musical scale context: non-uniform scales yielded better syntactic learning. This behavioral effect was mirrored by enhanced encoding of musical syntax in the context of non-uniform scales, which further suggests that their prevalence stems from fundamental properties of learning.