A two-decade review puts the foundations of beat perception in the newborn brain

In the newborn work the review leans on, the informative trial is the silent one. Recordings of newborn brain activity show responses to sounds omitted at metrically important positions, even when nothing louder marked those positions ^[6]. A loudness-detection account predicts no response there. The rival explanation is that the infant has learned which sound tends to follow which, and newer experiments indicate the responses cannot be explained by that statistical order alone ^[7]. What is left is an early sensitivity to periodic structure and to beat-based prediction ^[8].

The authors set the limit themselves. Neural sensitivity is not the same thing as conscious experience, and early timing capacities go on developing, so the review declines to credit newborns with fully mature beat or meter perception ^[9]. "Newborns are not miniature adult listeners, but their brains already seem prepared to use rhythmic structure to predict when something should happen," Honing said. "Experience does not create this capacity from scratch; it calibrates and enriches it" ^[10]. Across infancy and childhood, auditory exposure, motor development and musical enculturation improve the precision, flexibility and hierarchical organization of rhythmic processing ^[12].

Outside primates the record is thin. Synchronization has been observed in a small number of species, including some birds and a sea lion, and the review describes the evidence from nonhuman animals as sparse ^[15]. Rarity measured on a literature that small is partly a statement about how many species have been tested.

The human-versus-other-primate difference the review defends is one of degree and of integration among systems both groups have, since its GAER proposal has human beat perception emerging from tighter coupling of old auditory, motor, predictive-timing and reward systems ^[16][14]. A circuit humans alone possess would be a different claim. "The difference between humans and other primates may be not only whether they can match the tempo of the music, but whether synchronizing is intrinsically motivating and whether auditory, motor and reward systems work together strongly enough to stabilize prediction," Honing said ^[17].

Of the four claims the review examines, the phys.org account reports evidence bearing on three: spontaneous development, predictive timing, and distribution across species. It does not say what the authors concluded about near-universality across human cultures ^[20]. The summary verdict quoted there, that the available evidence does not justify every stronger claim made in the field, is not attached to any particular one of the four ^[5].

The authors ask for closely matched experiments across newborns, adults and other species ^[18]. They also want behavioral, neurophysiological, genetic and computational work alongside the neuropsychological methods that dominate the field, so that passive tracking of a stimulus can be told apart from internally generated prediction of a beat ^[18].