People believe their eyes over their ears, Duke research finds

jshaffer@newsobserver.comSeptember 8, 2013 

— It’s not often that the high-minded world of neuroscience collides with the corny, old-fashioned art of ventriloquism. One depends on dummies; the other excludes them.

But a Duke University study uses puppet-based comedy to demonstrate the complicated inner-workings of the brain and shows what every ventriloquist knows: The eye is more convincing than the ear.

The study, which appears in the journal PLOS ONE, seeks to explain how the brain combines information coming from two different senses. How, asks Duke psychology and neuroscience professor Jennifer Groh, does the brain determine where a sound is coming from?

In your eyes, the retina takes a snapshot, she said. It makes a topographic image of what’s in front of you. But the ears have nothing concrete to go on. They have to rely on how loud the sound is, how far away and from what direction.

That’s where a ventriloquist comes in, providing a model for this problem. With a puppet, the noise and the movement are coming from different places. So how does the brain fix this and choose where to look?

Duke researchers tested their hypotheses on 11 people and two monkeys, placing them in a sound-proof booth.

They arranged speakers in various locations and attached lights to them.

Then they played a sound from one speaker and flashed a light from another, tracking people’s eye movements. Sometimes they played the sound in time with the light, but only for just a fraction of a second. Sometimes they played the sound first, then followed up with the light.

Results: People moved their eyes much more when the light came at a different time with the sound. To sum up, it doesn’t matter if sounds and lights happen at the same time, in the same place. It’s more important that the eyes get a clue to give back to the brain.

“Vision is so much better at informing location,” Groh said. “Why do we have the ventriloquist illusion? That illusion occurs because of the power of vision to correct errors.”

This rings true to Cynthia Foust, a real ventriloquist in Rocky Mount.

She spent about six months practicing on her own before taking her show to day cares, where she aims to keep children’s eyes on the puppet’s mouth.

“You kind of keep things animated with the puppet so they’re not looking at me,” Foust said.

It’s not just an art. It’s a neuroscience.

Shaffer: 919-829-4818

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