Laurel vs Yanny Explained By a Neurologist

The Laurel versus Yanny debate quickly fascinated the online community worldwide and the debate continues. Neurologist Matthew Leonard from the University of California San Francisco joins Hari Sreenivasan via Google Hangout, to discuss the varying perceptions of Laurel versus Yanny.

TRANSCRIPT

[ Computerized voice saying 'Yanny/Laurel' ]

The Laurel versus Yanny debate quickly fascinated the online community worldwide, and the debate continues.

Neurologist Matthew Leonard, from the University of California, San Francisco, joins us via Google Hangout to discuss the varying perceptions of Laurel versus Yanny.

So, your field of study -- how does this help us explain what's happening when people hear this sound?

Yeah, so, the Laurel versus Yanny illusion is a really interesting example that actually tell us a lot about the work that our brains do to make a noisy and ambiguous world around us make sense.

So, just to kind of explain the illusion itself a little bit, the sound actually is ambiguous, and it actually contains all of the information for both the words 'Yanny' and 'Laurel.'

So, how we know that --

So they're both in there.

They're both in there.

Exactly.

So, sound and speech are made up of a lot of different frequencies that change over time.

You can kind of think of that like, you know, musical pitch or harmony.

And what happens is that the ears break down those sounds into those individual frequencies and pass that information along to the brain.

[ Computerized voice saying 'Yanny/Laurel' ] And then it's up to the brain to somehow interpret it and make sense of it for the listener.

So, when we actually look at the Yanny/Laurel sound itself, it just happens to be a really strong mix of the frequencies that make up both of those words.

If all of the information is in there, can you actually design sounds that would have multiple, well, words in it?

I had a feeling that it had something to do with particular combinations of frequencies that were making people hear it one way or another.

So, what I actually did was -- I took the sound file and I just completely removed all of the higher frequencies.

And the higher frequencies are actually the ones that more strongly resemble Yanny.

And so what I heard, when I removed those higher frequencies, was -- it actually switched for me, from sounding like 'Yanny' to sounding like 'Laurel.'

And when you do the opposite, removing the lower frequencies, you can change the perception from 'Laurel' to 'Yanny.'

So, this sound actually is a good example of that, where both of the words are there.

So, this was a case of our ears and our auditory senses thrown for a loop?

A few months ago, we had the case of the dress and how people perceived it.

That was kind of one of these scenarios that you're describing, but with our eyes.

Exactly. And I think, you know, that also just kind of highlights the fact that this is not something that we could call modality-specific.

So, really, you have these kinds of -- You know, we have the five senses, and each of those is connected to the perceptual systems of the brain.

And the perceptual systems, you know, are areas that we're very interested, in a lot of our work, to be able to understand, you know, not only how we sense the world around us and navigate it, but actually understand it.

How common are these sorts of instances where our sense perception is out of whack?

They're incredibly common.

Just in the auditory domain and even just the speech-and-language domain alone, it's actually incredibly common.

We've done some work with some of our colleagues to look at a phenomenon that's called phoneme restoration.

And the idea is that you take a word and you completely remove one sound from it and you replace that with noise.

So this is really analogous to if we're having a conversation, instead of you're in a quiet studio, I'm in a quiet office, we're out on the street corner.

There's traffic.

There's, you know, cars honking.

Or, if we're in a restaurant, there's a lot of commotion.

It's actually incredibly common for certain sounds not to even really reach the brain.

But we don't notice that.

Most of the time, we just go on as if we heard something.

And so, in this phoneme restoration, we've kind of -- There's a way that you can kind of stimulate that.

And what we've done in our work is -- we've looked at how some of the perceptual regions of the brain respond to that sound when it's perceived one way or another.

Does this happen often as we walk through life or is this just these kind of outlier cases, and thanks to social media that we're sharing it and we're seeing it?

I mean, I think the Yanny/Laurel example is kind of an extreme case of this, where my understanding is that the sound itself was just -- The actual word that was recorded was 'Laurel,' but through the way that the sound was recorded on a phone or something like that, there was some interference that was introduced to it, and it kind of distorted the frequencies a little bit.

But there are definitely just everyday examples of these kinds of ambiguities that exist all over the place.

All right.

Matthew Leonard, from the University of California, San Francisco, thanks for joining us.

Thank you.