We are wired to respond to sound in a thousandth of a second. With that kind of visceral, automatic response we sometimes get it wrong. I’ve been looking at the research of perceptual and cognitive psychologist Diana Deutsch. She has spent her career exploring and assembling audio illusions and curiosities. We’ll look at a few of them together and ask “can you trust your ears?”
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I posed the question to some of my colleagues at VPR. They volunteered to experience a few audio experiments with me.
James: Why don’t you give your names?
Brendan: My name is Brendan Kinney.
Joe: Joe Tymecki.
Leslie: and I’m Leslie Blount.
James: Okay guys. So, this first one is kind of an internet meme. It’s gone around a lot.
Leslie: Okay.
James: Do you remember the dress? Is it blue? Is it…
Brendan: Right.
Leslie: Yeah.
James: Ok. What name do you hear?
Brendan: Laurel.
Leslie: I heard Laurel too.
Joe: (chuckles) Laurel.
James: You hear Laurel?
Joe: I hear Laurel.
Some people hear Laurel and some hear Yanny. What about you? Listen to that audio sample again. Unlike the famous image of the dress, which has to be one color or the other, this audio sample actually does contain both names simultaneously. Yanny and Laurel are separated by high and low frequencies. There is almost a 50/50 split between those that hear Laurel and those that hear Yanny. It all depends on what frequencies you are personally tuned into. I personally always hear Laurel unless I slow down the audio 25 percent then Yanny comes into focus.
This next experiment is best experienced with head phones. I’ll play you a simple melody in one ear and then the other. Once again, listen to the way the melodies bounce around a little bit in one ear and the other. Now, I’ll play both audio samples at the same time in both ears. Did you hear what happens? It’s the same exact bouncing melodies, but when experienced together they produce a simple scale moving in contrary motion. This is called the Deutsch Scale Illusion. Our mind is rigged to perceive patterns and it will automatically place similar notes together in a line. That’s the power of this illusion, to make you hear a scale when neither audio sample is playing it.
Let’s listen to one more audio experiment called the Shepard-Risset Glissando. The challenge is to follow a single pitch all the way down to the bottom… you’ll see what I mean.
Joe: Obviously, I hear notes descending and then at some point it seems like I just lose track of where it is and my ear sort of resets up to some higher note again and just like, locks on a higher note.
Leslie: I was hearing… my mind made me think, and you said glissando, that the note was going down but as I listened to it, it’s just layered.
Brendan: It never hit bottom.
Leslie: It never went down, right? It just stayed. And the longer I heard it I was like, wait a minute. We’re just staying right where we were.
Brendan: Right.
Leslie: It just had this depth to it.
The Shepard-Risset Glissando is a bit like an old fashioned barber shop pole spinning in place, creating the illusion of infinite motion. The reality is we have a limited frequency range that our ears can perceive and as the low notes go down below our hearing, new notes replace them from above. Our mind perceives the loop.
These experiments point to some limitations of our hearing and perception. In our next episode we’ll look at some of the ways our minds can fill in the gaps of what we’re hearing. Until then we’d love to hear from you. Let us know what you think and you perceive in the “Yanny/Laurel” experiment or the scale and glissando illusions.
Timeline is an exploration into the development of Western music.
