Dr. Jennifer Groh

And I think one of some of my favorite videos for, you know, for really appreciating this is our videos of actual ventriloquists working with their puppets.

Because there they are, you know, the puppeteer is speaking and they're making it seem like the puppet is speaking.

And they're making our perceptions switch back and forth from their own face to the puppet face, back and forth, depending on what they're actually saying.

Yeah, they try to speak like this without moving their lips too much.

And they sometimes will do a trick of like, there are certain sounds that you just cannot make without closing your lips in front.

And that's really...

hard to fool people about.

So for example, if it's a word that begins with a B or has a B in it, they might subtly just cover their mouth a little bit while they're making that B sound so that it's a kind of misdirection like a magician would do to sort of keep you from attending too much to the ventriloquist.

and throw your attention over to the puppet.

So our perception can switch back and forth between where our brains are telling us this is the most likely candidate for the source of this sound.

So I'm gonna override what my ears are telling me to perceive the sound as coming from here versus here.

It has to be learned and it has to be continuously updated during the course of development until you reach your adult body size.

So let me back up a little bit and talk about how do we localize sound, especially when we're not talking about, you know, screens and video and movies and whatnot, but just like out there in the real world.

The way we tell where a sound is coming from is by the physics of the world causing differential delays for the sound to arrive at one ear versus the other.

So sound takes a certain amount of time.

You know, a sound coming from over here will get to this ear before it gets to this ear.

And it'll be slightly louder in this ear than in this one.

It's closer, but also there's a kind of acoustic shadow cast by the head.

So the sound wave has to kind of come and then go around and there's a little, you know, there's a little sort of dip in the sound intensity cast by the shadow of the head.

I like to think about the timing cues because they're really easy to calculate.