How Sound Shaped The Evolution Of Your Brain
September 10, 2015
http://www.npr.org/sections/health-shots/2015/09/10/436342537/how-sound-shaped-the-evolution-of-your-brain
“Vibration sensitivity is found in even the most primitive life forms,” Horowitz says — even bacteria. “It’s so critical to your environment, knowing that something else is moving near you, whether it’s a predator or it’s food. Everywhere you go, there is vibration and it tells you something.”
“You hear anywhere from 20 to 100 times faster than you see,” Horowitz says, “so that everything that you perceive with your ears is coloring every other perception you have, and every conscious thought you have.” Sound, he says, “gets in so fast that it modifies all the other input and sets the stage for it.”
It can do that because the brain’s auditory circuitry is less widely distributed than the visual system. The circuitry for vision “makes the map of the New York subway look simple,” says Horowitz, whereas sound signals don’t have as far to travel in the brain.
And sound gets routed quickly to parts of the brain that deal with very basic functions — “precortical areas,” Horowitz says — that are not part of the wiring for conscious thinking. These are places where emotions are generated.
“We’re emotional creatures,” Horowitz says, “and emotions are evolutionary ‘fast responses’ — things you don’t have to think about.”
That speediness pays dividends in the survival department: “You hear a loud sound?” he says. “Get ready to run from it.” Emotions are rapid delivery systems in the brain, and sound drives emotions.