When it comes to memory for music, humans show an interesting quirk: we’re better at remembering melodies that are sung by voice, compared to those played on an instrument. Even a melody sung without any lyrics — just a series of la la las, for instance — becomes lodged in our memory in a way that a tune played on the piano, say, does not.
Now a new study published in Cognition has looked into why our memory is so much better for sung melodies. Researchers have suggested that listening to a voice singing a melody leads us to perform “subvocalisations” — internal speech that involves tiny movements of the muscles involved in speaking (you’re probably doing it right now as you read this text). But we can’t mimic an instrumental piece in the same way. After all, it’s easy to repeat “la la la” in your head, but not to reproduce the sound of piano keys.
Psychologists already know that this kind of silent rehearsal boosts memory for words — and that memory is impaired if we speak or make movements of the mouth and tongue, which interferes with these subvocalisations. So, theorised Michael Weiss and colleagues at the University of Montreal, if a similar process is responsible for our superior memory for vocal melodies, then people’s memory should be compromised if they make other mouth movements or sounds while listening.
In the first study, the team asked 38 participants to listen to 24 melodies, which were based on British and Irish folk tunes. Half of the tunes were played on the piano, and half were sung (as “la la la”). While listening to the melodies, half of the participants chewed gum vigorously, while the others squeezed a bean bag with their hand.
After taking a break to fill in questionnaires, the participants then completed a surprise recognition task, in which they heard the same 24 melodies as well as 24 new ones. They simply had to indicate whether or not they had heard each tune previously.
Similar to the findings of past work, participants were better at recognising the vocal melodies than the piano ones. But this “voice advantage” was the same whether participants had been chewing gum or squeezing the bean bag while listening. That is, the chewing motion — which uses the same muscles as articulating a word— had no effect on participants’ memory, suggesting that silent rehearsal wasn’t responsible for their superior recognition of the sung tunes.
Still, chewing gum is considerably different from actually mouthing words or making sounds, so might not be enough to interfere with any subvocalisations. So next, the team asked a new group of participants to either mouth “la” over and over again (without making any noise), or make a humming sound. In a subsequent study, participants whispered “la la la”.
In both studies, participants still recognised the vocal melodies better than the piano ones, despite making mouth movements or sounds. This again suggested that silent rehearsal of the sung melodies wasn’t responsible for boosting participants’ memories.
It’s worth noting that there wasn’t a control group in either of these studies, which makes it hard to completely rule out the possibility that making mouth movements or sounds could have reduced memory for vocal melodies, even if it didn’t entirely get rid of the memory advantage over instrumental tunes. However, the team did compare their results with an earlier study, in which participants listened to vocal and instrumental melodies without doing a task, and found no difference in memory performance between the two papers.
Overall, then, the studies suggest that our superior memory for sung melodies isn’t down to internal, silent rehearsal of the tunes. So what could explain the effect? Well, perhaps it’s just that humans are more attuned to voices than other sounds, the authors say. “The best current account of the voice advantage in memory remains that the voice is special, by virtue of being a conspecific, communicative, and biological signal, which is more engaging or distinctive to listeners than instrumental sounds,” they conclude.