Music is characterized by acoustical forms that are predictive of its behavioral functions. For example, adult listeners accurately identify unfamiliar lullabies as infant-directed on the basis of their musical features alone. This property could reflect a function of listeners' experiences, the basic design of the human mind, or both. Here, we show that American infants (= 144) relax in response to 8 unfamiliar foreign lullabies, relative to matched non-lullaby songs from other foreign societies, as indexed by heart rate, pupillometry, and electrodermal activity. They do so consistently throughout the first year of life, suggesting the response is not a function of their musical experiences, which are limited relative to those of adults. The infants' parents overwhelmingly chose lullabies as the songs that they themselves would use to calm their fussy infant, despite their unfamiliarity. Together, these findings suggest that infants are predisposed to respond to universal features of lullabies. Music is a human universal 1-3 that appears often in the lives of infants and their families 4-8. Infants demonstrate a remarkable variety of responses to music as they develop: in the first few days of life, newborns remember melodies heard in the womb 9 ; distinguish consonant from dissonant intervals 10 ; and detect musical beats 11. Older infants differentiate synchronous movement from asynchronous movement in response to music 12 ; become attuned to the rhythms of their native culture's music by their first birthday 13 ; garner social information from the songs they hear 14,15 ; and recall music in impressive detail 16,17 after long delays 14. Why are infants so interested in music? One possibility centers on the dynamics of parent-offspring interactions. Relative to other animals, human infants are helpless; to survive, they rely on resources provided by parents and alloparents 18. Such resources, whether material (like food) or not (like attention) constitute parental investment 19. Human parental investment is routinely provided to infants in response to their elicitations, which often take the form of fussiness and crying 20. Infant-directed songs may credibly signal parental attention to infants, conveying information to infants that an adult is nearby, attending to them, and keeping them safe 21,22. Singing indicates the location, proximity, and orientation of the singer (even when the singer is not visible, as at night); and it is also costly, in that the singer could be expending their energy on some other activity. Because parental attention is a key resource for helpless infants, they likely are predisposed to attend to signals of it: infants should be particularly interested in and reassured by vocal music with features suggesting that it is directed toward them. Studies of people with genomic imprinting disorders provide a unique test of this hypothesis because these disorders are characterized by divergent behaviors related to parental investment 23,24. For example, infants with Prader-Willi syndrome eli...

Music is characterized by acoustical forms that are predictive of its behavioral functions. For example, adult listeners accurately identify unfamiliar lullabies as infant-directed on the basis of their musical features alone. This property could reflect a function of listeners’ experiences, the basic design of the human mind, or both. Here, we show that American infants (N = 144) relax in response to 8 unfamiliar foreign lullabies, relative to matched non-lullaby songs from other foreign societies, as indexed by heart rate, pupillometry, and electrodermal activity. They do so consistently throughout the first year of life, suggesting the response is not a function of their musical experiences, which are limited relative to those of adults. The infants’ parents overwhelmingly chose lullabies as the songs that they themselves would use to calm their fussy infant, despite their unfamiliarity. Together, these findings suggest that infants are predisposed to respond to universal features of lullabies.