The scientific reason we hear a sentence like a song when it's repeated over and over

  • If you say the same set of words over and over, it can start to sound like a song.
  • This can happen with random sounds too, which are perceived as having more of a song-like quality than if the sequence is played just once.
  • Researchers from the University of Kansas have tried to work out what’s happening in the brain.
  • Essentially, we have different nodes for words and syllables, and when the word node gets tired, the syllable one takes over – so we focus on the rhythm rather than the meaning.
  • Illusions are a unique way to get another angle on what’s going on in the brain and remind us that perception is subjective.

Repetition has an interesting effect on the brain. If you keep hearing a sequence of numbers – like 4, 8, 15, 16, 23, 42 – chances are it will eventually stick.

But it can feel like repetition bends reality sometimes too. For example, hearing a phrase over and over again can make it sound musical. New research from the University of Kansas has looked into why this might be.

The study, published in the journal PLOS ONE, investigated this “speech-to-song illusion,” which scientists started investigating in the 90s.

“The illusion occurs when a spoken phrase is repeated – but after it’s repeated several times it begins to sound like it’s being sung instead of spoken,” said Michael Vitevitch, a professor and chair of psychology at KU.

Previous studies have found that brain regions that process speech are active when a phrase is perceived as such, but different areas that process music fire when it is heard as a song. You can listen to the illusion here:

“But nobody had a good explanation about how this illusion was coming about in the first place,” said Vitevitch.

Along with his team, Vitevitch designed six studies to look for what could be happening in the brain when words turn into song. They tested the “node structure theory” in 30 participants, which is where word nodes and syllable nodes act as “detectors” and recognise the different aspects of syllables, words and phrases.

“You’ve got word detectors and syllable detectors and, like with lots of things in life, as you use them they’re going to get worn out – like your muscles. As you use them, they get tired,” Vitevitch said. “Like with muscles, you have a type of muscle for short bursts of sprinting and also muscles for endurance, like running a marathon. Word nodes are like sprinting muscles, and syllable nodes are like endurance muscles.”

Woman commute train listening to music headphones subwayDean Drobot/Shutterstock

Results suggested that initially when hearing the words, word detectors are activated, giving the perception of speech. But they get tired as the phrase is repeated, so when you continue to hear the same words over and over, the syllable detectors are activated. After a while, this shifts our perception of hearing a song, because syllables are associated more with the rhythm of language than individual words.

“We tried to strip musicality away by randomly putting words together without intonation shifts, so it didn’t sound musical at all, to begin with,” said Vitevitch. “When people hear it once, they said it didn’t sound musical at all. The fact that we could get people to shift perception to something musical after several repetitions gives us confidence that we’re on the right track with the mechanism explaining the effect.”

Perception is an important part of language, and it can sometimes seem like our minds are playing tricks on us – like with Yanny and Laurel. For example, cognitive scientist Elizabeth Hellmuth Margulis described in her work how we prefer a song when we’ve heard it before, and how familiar statements are more likely to sound true than unfamiliar ones, with something called the “mere exposure effect.”

Strange things happen with individual words too, like semantic satiation, which is when repeating a word ad nauseam can make you stop focusing on what the word means and instead listen to the sounds – which is why people tend to say the word has “lost all meaning.”

“Everyone is built a little differently so there will be some variation in how much one experiences this (or any other) illusion,” Vitevitch told Business Insider. “In the case of the speech to song illusion if the rate at which the words are presented matches the rate at which your word detectors fatigue then you are likely to experience this illusion, but if your detectors are set differently you might not perceive the illusion as strong as someone else does, or even at all.”

Researchers are all trying to understand how things work, whether that’s the universe, the brain, or individual atoms, Vitevitch said. And illusions are a unique way to get another angle on what’s going on.

“Whatever a particular scientist is trying to study in nature ‘Mother Nature’ hides her secrets very tightly from the prying eyes of a scientist,” he said. “Things like illusions, which most people dismiss as simply a party trick or something like that, actually are useful and allow scientists to peek behind the curtain to see how things actually work.”

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