It’s an epic auditory insult. Akin to: I say tomato and you say “blow it out your ear.” I just listened to the new amazing illusion, in which about half of the denizens of my current café hear a voice say “Yanny” whereas I clearly hear “Laurel.” It’s a magical-seeming deception that seems innocent when you hear it. But it reveals itself as mysterious—and a little bit sinister—when you ask your friends, listening to the same recording at the same time, what they hear, and its totally different from what you hear. Try it now:

My wife agrees with me—Laurel—saving our marriage from otherwise certain divorce—but our three rotten kids instead all hear “Yanny.”

So what is going on? We’ll have to find out when neuroscientists around the world start digging in to determine its neural underpinnings of this equivocal percept in the lab. But this is what we can tell you at this time, drawing some inferences from equivalent visual illusions, like The famous Dress that took the world by storm in February of 2015.

Dress Illusion, about half of the world’s population sees a white-gold dress, whereas the other half sees a blue-black dress. Like the Yanny-Laurel Illusion, nothing at first seems amiss, until you start talking to somebody about your experience and discover that their sensation is completely different from yours.

Since The Dress came out, we’ve learned a number of facts that have shed some light on why the illusion occurs, though the full mechanistic pathway remains incompletely known. First, scientists have determined that the colors at play in the dress are critical: it only happens with colors along the blue-yellow axis of the color-wheel. This makes good sense, from an evolutionary biology perspective, if you consider that our color vision evolved during the daytime: everything we ever saw in the history of our species was either yellowish (illuminated by direct sunlight) or bluish (seen under scattered light, shaded from the sun). So The Dress looks White/Gold when you perceive that the garment is in the shade, whereas it looks Blue/Black when you perceive it to be under direct sunlight.

What was new about The Dress wasn’t its inherent ambiguity: dozens of color illusions already existed where observers perceived red as green and yellow as blue. What was mysterious about The Dress is that half the people saw it as in the shade, and the other half as in the sun. Scientists have looked hard for an explanation and thus far there is no consensus on how or why the human population got split along this tectonic fissure.

So what is the deal with The Yanny-Laurel illusion? Well, it’s clearly an ambiguity illusion, which is nothing new to auditory science. Ambiguous auditory percepts have been known for quite some time. But, as with The Dress, it’s far less common for different individuals listening to the same sound clip on the same device to hear it differently from each other. Usually when an ambiguity is introduced, everybody within earshot hears the ambiguous sound bite in the same way. That’s what occurs, for example, in The McGurk Effect, in which the visual system and the auditory system interfere with each other to create a sound that was never uttered. In one such scenario, you see a face say the word “ba,” while a sound is simultaneously played “da.” What you hear—really hear as if with your ears—is “badah.” Everybody watching the screen with their eyes and ears open hears it the same way. Which of course only existed in their minds, which conflate the visual with the auditory.

Already scientists have begun to dissect the Yanny-Laurel effect. Brad Story from University of Arizona reported in Zöe Schlanger’s article in Quartz that auditory analysis of the sound clip reveals clear points of physical ambiguity, which Zöe concludes explains the effect. But the physical basis for the ambiguity may not be the most scientifically interesting, but the fact that different people hear it differently. The question that remains unasked and thus unanswered is: do half of us hear Yanny, and half of us Laurel, because of our assumptions about the speaker or the environmental sound conditions? And if so, why does that happen and why are we dissimilarly predisposed into different groups?

Perhaps the Yanny-Laurel Illusion will divide humanity down the middle like cat vs dog people, glass-half-full vs glass-half-empty people, and for the same unknown reasons. We just don’t yet know.