Lyrics don’t matter in a good lullaby

Babies love lullabies and they aren’t fussy about what language we sing them in, a new study suggests.

When researchers at Harvard University played 16 songs from regions as diverse as Polynesia and the Middle East – and sung in everything from Scottish Gaelic to Native America Hopi – the results were largely the same.

The US infants responded to the universal elements, despite the unfamiliarity of the melodies and words. And they relaxed.

“There’s a longstanding debate about how music affects listeners as a result of both prior experiences with music and the basic design of our psychology,” says Samuel Mehr, from Harvard’s Music Lab.

“Common sense tells us that infants find the lullabies they hear relaxing. Is this just because they’ve experienced their parents’ singing before and know it means they’re safe and secure, or is there also something universal about lullabies that produces these effects, independently of experience?”

The new findings, published in the journal Nature Human Behaviour, support the latter hypothesis.

In the experiment, each infant watched an animated video of two characters singing either a lullaby or a non-lullaby and the researchers measured pupil dilation, heart rate changes, electrodermal activity (electrical resistance of the skin), frequency of blinking, and gaze direction as indicators of relaxation or agitation.

Generally, they report, the infants experienced a decrease in heart rate and pupil dilation, and attenuated electrodermal activity in response to the unfamiliar lullabies.

The songs were chosen through a previous study and included lullabies and other songs originally produced to express love, heal the sick, or encourage dancing.

Separately, researchers asked parents to listen to both types of song and choose which they would use to soothe their infant. They almost always chose the lullaby, the researchers say, indicating that they also recognised the universal elements of the lullaby, even subconsciously.

They acknowledge that the study only looked at one cultural group (known as WEIRD, for Western, educated, industrialised, rich and democratic) but are confident they could be replicated more broadly.

They also plan to investigate questions raised during the experiment, such as which of the acoustical elements of a lullaby encourage relaxation, how singing interacts with other activities and environments to induce relaxation, and what inferences infants might make during listening.

“While the music in general was relaxing, there was something about the lullabies that was especially relaxing, so in theory there could be ways to optimise the music we provide to infants, to make them more effective,” says co-lead author Connie Bainbridge.

“Additionally, it’s an interesting area to explore as far as the function of music; is it an adaptation that we evolved to have or a by-product of language or auditory cognition?

“Our findings do seem to support the idea that there is actually an evolutionary function of music.”