Yanny or Laurel? Science explains why you’re hearing one and not the other

On Tuesday, the internet broke out into an all-consuming debate, dividing people into two camps: those that heard “Laurel,” and those that heard “Yanny.”

The factioning began when social media influencer and vlogger Cloe Feldman tweeted a simple question about a short piece of audio: “What do you hear?! Yanny or Laurel?”

From then on, like “The Dress” three years before it, the internet split itself in two. One group was adamant that the voice in the audio clip was saying, “Yanny.” The other group would bet their firstborn the voice was saying “Laurel.”

In a YouTube video, Feldman explained the post originally came from Reddit, and she then posted it to Twitter. The original Reddit post appears to have been uploaded by a user who goes by RolandCamry, who said the word originated on Vocabulary.com.

The original word on Vocabulary.com is “Laurel,” but according to a reply RolandCamry posted on Reddit, his sister heard the word “Yanny.”

However, Marc Tinkler, chief technology officer for Vocabulary.com, said a student in Georgia was the first person to notice the auditory illusion. Tinkler said the website started as a project for high school students and the fact that one discovered the now-viral phenomenon “makes us happy.”

Feldman and RolandCamry did not respond to interview requests from NBC News.

Poppy Crum, chief scientist at Dolby Laboratories, said a number of things are causing the divide in the great Yanny/Laurel debate.

First, there’s a simple explanation as to why some people hear “Yanny” and some people hear “Laurel.”

What do you hear?! Yanny or Laurel pic.twitter.com/jvHhCbMc8I

— Cloe Feldman (@CloeCouture) May 15, 2018

Literally everything at my show just stopped to see if people hear Laurel or Yanny. I hear Laurel. https://t.co/efWRw1Gj0L

— Ellen DeGeneres (@EllenDeGeneres) May 15, 2018

“People who hear or weight high/mid-high frequency more strongly will hear ‘Yanny,'” Crum said. “The perception of ‘Laurel’ is experienced when the lower frequency information is dominant in the experience.”

But there are other reasons, Crum said. Human beings perceive sound differently on a physiological level. This can be attributed to age, gender and other personal demographics that determine how we hear sound. Additionally, external elements like language and dialect can create biases in interpreting sound that change the perceptions in different people.

“Language, dialect, exposure to relevant sounds in someone’s environment, and even gender from the content of our own voices can alter how we experience the exact same information,” Crum said.

This is why two people could be sitting together listening to one device and still hear different things.

“We each have a different cookie cutter in how our brain is interpreting this information, which influence how we hear things differntly than another person,” Crum said.

Crum also said another influence on people’s perceptions is the device they listen to the sound on.

“Obviously, what you hear is influenced by what playback device you have because that will alter frequency of that sound,” she said.

"I said it's #Yanny, recruit, not #Laurel!"

A @USMC Drill Instructor corrects a recruit after completing the rappel tower on Parris Island, #SouthCarolina. #KnowYourMil #Marines pic.twitter.com/XRhmsB4KiG

— Department of Defense 🇺🇸 (@DeptofDefense) May 16, 2018

it's so clearly laurel. I can't even figure out how one would hear yanny.

— chrissy teigen (@chrissyteigen) May 15, 2018

But the final piece of the puzzle is how the human brain categorizes sound and language. Crum said the human brain puts sounds into categorical boxes, especially when it comes to language.

“You could imagine a situation — if every subtlety with how someone pronounces a vowel, if you had to get it just right, that would be really unproductive,” Crum said. “Instead, you can have a lot of sounds that are very similar, and our brain wants to homogenize them more than they might be at a fundamental stimulus level, and something like that has happened here.”

As for where Crum falls in the Yanny/Laurel debate?

“I hear Yanny all the time even though I know it’s the wrong word, but that’s my perceptual reality,” she said. “It is what it is.”