'Yanny' or 'Laurel'? Why Your Brain Hears One or the Other in This Maddening Illusion

This article was updated at 4 p.m. ET.

An auditory illusion that's making the rounds online seems to have divided people into passionate camps depending on whether they hear the word "Yanny" or "Laurel" when listening to a recording.

If you hear one, you don't hear the other, and you'll be convinced the audio clip could only be saying … "Laurel" (in my case). Are you #teamyanny or #teamlaurel?

There's some science to suggest that depending on how you look at the explanation, either both teams are correct or neither are. That's because no "true" word has been recorded, Andrew Oxenham, a professor in the Departments of Psychology and Otolaryngology at the University of Minnesota, told Live Science.

The illusion first popped up on Reddit a few days ago. It is being likened to the famous dress debate of 2015, in which some people swore the garment was black and blue and others said it was white and gold. According to a study of that illusion, people saw the different colors because of assumptions the brain made about the illumination of the dress under different lighting conditions.   

Filling in missing information

What do you hear when you listen to the audio clip?

This latest "illusion," although based on auditory perception and not vision, also likely boils down to the brain's wackiness. One idea is that, if there is any ambiguity about a sound or word, the brain will lock onto one word or sound and deem that the correct interpretation. When there is a "perceptually ambiguous stimulus," the University of Sydney's David Alais told The Guardian, "the brain locks on to a single perceptual interpretation. Here, the Yanny/Laurel sound is meant to be ambiguous because each sound has a similar timing and energy content — so, in principle, it's confusable."

Alais, who studies audiovisual perception, added, "All of this goes to highlight just how much the brain is an active interpreter of sensory input, and thus that the external world is less objective than we like to believe."

Researchers are saying it's the auditory version of the so-called Rubin's vase, an image that is visually ambiguous and can be interpreted in one of two ways: as the profiles of two people, or a vase, according to various news reports on the illusion. [The Most Amazing Optical Illusions (and How They Work)]

Because your brain plays tricks on you here, your expectations about what you'll hear, or even your past experiences, could shape whether you feel strongly about Team Yanny or Team Laurel, The Guardian reported.

In addition to sending vital auditory clues to your brain, your ears play a role in this maddening Yanny/Laurel interpretation. Each sound is made up of several frequencies, and those that create "Yanny" are higher than those for "Laurel," said Lars Riecke, a cognitive neuroscientist at Maastricht University in the Netherlands, as reported by The Verge. The speakers you're using may change the frequency, leading to the different interpretations, he added.

But your ear shape and your age could also play roles. Turns out, as people age, they start to lose the ability to hear the higher sounds, so they may be more likely to hear "Laurel," which was the case for Alais, who is 52.

Sound frequencies

"Basically, there is no 'true' word and the stimulus has 'clues' based on the formant frequencies that point to either one or the other word," Oxenham said. A formant refers to the frequencies that carry the most energy when a sound is made, and they depend on the different parts of a person's vocal tract.

The shape of the tract and the resulting frequencies that come out when a person speaks are due to the placement of the tongue, according to psycholinguist Suzy Styles of the Nanyang Technological University, who tweeted about the Yanny/Laurel puzzle.

It seems like a speech synthesizer must have created the clip, according to Oxram and Styles. In normal speech, Styles tweeted, there are three formants that a person produces, but in this clip, there are more than three.

"So unless this speaker had two completely separate tongues, this ambiguous speech has been carefully crafted to fool the ears. Shall we call it an Ear-llusion?," Styles tweeted.

Reportedly, if you mess with the sound on your speakers to remove the high frequencies, you'll hear "Laurel" and vice versa when you remove the lower frequencies.

Why Laurel or Yanny?

As for what makes a person sway one way or the other after listening to this audio clip, that's anyone's guess for now.

"I'm not sure that anyone knows why some people hear it one way and other people hear it another way, but that's often the way with these visual and auditory illusions — our brains 'fill in' missing information, and how that happens seems to vary a lot from one person to the next," Oxenham said.

Bharath Chandrasekaran, an associate professor in the Department of Communication Sciences and Disorders at the University of Texas at Austin, said he doesn't know either, but he's planning to find out. He told The Verge that he is going to look for volunteers in both camps and then run tests in which he looks at their brain waves while they listen to the audio clip.

So, which camp are you in?

Update: Bad news for Team Yanny: The New York Times tracked the original source of the soundbite to vocabulary.com, where a computer-generated voice offers the pronunciation of the word... laurel.

Original article on Live Science.

Jeanna Bryner
Live Science Editor-in-Chief

Jeanna served as editor-in-chief of Live Science. Previously, she was an assistant editor at Scholastic's Science World magazine. Jeanna has an English degree from Salisbury University, a master's degree in biogeochemistry and environmental sciences from the University of Maryland, and a graduate science journalism degree from New York University. She has worked as a biologist in Florida, where she monitored wetlands and did field surveys for endangered species. She also received an ocean sciences journalism fellowship from Woods Hole Oceanographic Institution.