Does the language of a lullaby play a role in soothing infants?

Written by Karen M. Johnston, MD, Ph.D., Neurosurgery

In a recent Nature and Human Behaviour issue Bainbridge et al (1) challenge the reader with the idea that lullabies in many (most?) languages have the ability to soothe an infant despite the baby not recognizing the music or the language. As with our International Association for Music and Medicine, the study benefits from an approach and authorship that is multidisciplinary, multi centered and international.

Their introductory review of the literature highlights a variety of responses to music seen in infants, citing examples at multiple stages of infant development. They describe that infants may remember melodies, intervals and rhythms of their native culture music. This may be thought to be part of the parent-offspring interaction. The authors point out that infant directed songs likely signal parent attention, proximity and reward.

Additionally the authors offer medical models and across species examples of the relevance of this issue. They describe how across cultures infant-directed versus adult-directed speech are acoustically different and introduce the example of lullabies. Lullabies are recognized by adults as soothing to a baby and across cultures are distinguished by “slow tempos and smooth minimally accented melodic contours” (2).

The thought is if a lullaby conveys parental attention, the baby should experience relaxation. Indeed this has been shown if the songs are familiar and in a familiar language. In this most recent paper, the authors raise the interesting question as to whether or not this effect is also seen when these elements are unfamiliar to the infant.

About the Study

The study includes 144 infants from the United States. In order to investigate these questions, they look at known relaxation effects including:

• heart rate
• pupillometry (pupil dilation)
• electro dermal activity

The music includes eight lullabies in eight languages from around the world. They pair these with other song types as controls including dance, love and healing songs recorded from 86 world cultures, all from The Natural History of Song Discography. The music is presented acapella and in solo voice. The infant is introduced to the music via videos of an animated character who lip-syncs the song.

Results

They present their compelling findings that infants from 2-14 months indeed relax to unfamiliar lullabies. According to them, there is a “core set of acoustic features that is associated with infant-directedness.” This occurs across cultures and produces the relaxation effect.

In fact, the parents also chose the lullaby rather than the non-lullaby without being familiar with the music. The authors propose this supports a universal role for infant-directed song in parental investment.

Future

The authors leave the reader with three interesting questions.

• First, what features of the lullaby make it relaxing for the infant and is this reflected in a response to music as an adult?
• Second, is there an interaction with other features of the infant world example environment, rocking, and/or stories?
• Third, is there a role for social preference for the singer or caregiver?

We look forward to learning more as the answers to these questions are revealed. Let us know what you think about these very interesting findings in the comments!

1. Bainbridge C, Bertolo M, Younger J, Atwood S, Yurdum L, Simson J, Lopez K, Xing F, Martin A, Mehr, S. Infants relax in response to foreign unfamiliar lullabies. Nature Human Behaviour. 2020 Oct 19. doi: 10.1038/s41562-020-00963-z. Online ahead of print
2. Mehr S et al Universality and diversity in human song. Science 366, 957-970, 2019