Infants are soothed by unfamiliar and foreign lullabies

A lullaby in any other language would send me off to sleep...
26 October 2020

Interview with 

Constance Bainbridge and Mila Bertolo, Harvard


Two twin babies sleeping.


As exhausted parents know, at 3am it feels like there’s nothing more important than soothing a crying baby, and a lullaby can sometimes do the trick. Incredibly, it turns out that your baby doesn’t have to understand the language, or even be familiar with the music style, to nevertheless find lullabies relaxing, as Eva Higginbotham heard from Mila Bertolo and Constance Bainbridge...

Constance - So we wanted to see if listening to these lullabies would relax infants compared to songs that were not lullabies. And that was indeed what we found.

Eva - What age were the babies that you were looking at?

Constance - We looked at babies from the ages of 2 months up through 14 months. And we did actually make sure that we had an even distribution in each age category so that we could examine for age effects, which we did not find, which is super interesting because this suggests that the response to these lullabies is not something that the infants learn during that first year of life, but there might actually be some inclination to relax to these from a very early age. We had animated characters sing these songs to the infants that came into lab. All of these songs actually come from the Natural History of Song discography which is from previous research in our lab. And these songs include small scale societies, they're really scattered across the world. And the songs include these lullabies as well as dance songs, love songs and healing songs.

Eva - Mila, you also worked on this project. How did you actually collect the data from the babies to see if they were being soothed by the lullaby?

Mila - When the babies came into the lab, before we sat them in their seat where they watched this little animation and heard these songs, we fit them with a little monitor that's similar to a Fitbit that recorded their heart rate and electrodermal activity, which is this measure of sweat gland activity, which is basically how excited you are. And in real time, while they were listening to the songs, we could track how their heart rate and electrodermal activity was changing in response to those songs.

Eva - How long were the songs? Because I would imagine that it would take a few minutes for music to produce a, you know, a calming or an exciting reaction. Is that what you found or were they just short clips of songs?

Mila - The clips of songs that we used were only 14 seconds each and they alternated pretty rapidly. So obviously in the real world, infants' experience of music is much richer. They listen to music for minutes on end, in their parents' laps and things, but in order to really isolate any possible effect that purely musical features might have, we chose to snip down the songs to about 14 seconds each and to alternate them, just to see if the infants were immediately reactive to the musical features.

Eva - And what did you find?

Mila - There was a main effect that if you compare their heart rates between the lullabies and the non lullabies, we found that the heart rates dropped in response to the lullabies and something similar also in their electrodermal activity where it was lower during the lullabies relative to the non lullabies.

Eva - And you've actually sent me some samples to listen to. And this is your favourite lullaby, right?


Eva - Oh, it is very relaxing isn't it? And then the babies would have listened to that, and also to this other song, it's a love song I think

Love song

Eva - Yeah, certainly sounds passionate! Were you surprised by the results and what might this tell us about how humans actually relate to music?

Mila - I think this result really is quite surprising. On the face of it it might seem pretty obvious that of course lullabies are soothing, but it's actually not at all intuitive that what we as kind of Western listeners deemed to be relaxing, musical patterns are the same musical patterns that people in other societies would find relaxing.

Constance - It is potentially surprising that even across many different cultures, producing vastly different music in other dimensions, that these lullabies still have something about them that makes them recognisable. And I think one of the coolest things about this is this may very well suggest that there is actually an evolutionary function to lullabies. So sometimes there can be debate over, is music just this sort of, in the words of Steven Pinker, "auditory cheesecake"? Is it just something fun that we kind of came up with as a culture? Or is there actually a purpose to music? And maybe lullabies are one of the first links for us to kind of get to that question.


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