It is common knowledge that a speaker's gestures can help the listener to follow thes story. What is less well known is that gestures can also help the storyteller, as discussed in an article in today's Wall Street Journal:

Sitting in her office at the University of Chicago, Susan Goldin-Meadow is gesticulating nonstop as she talks to me, which wouldn't be particularly noteworthy except for two things.

Prof. Goldin-Meadow is one of the world's leading scientific experts on the meaning and function of the hand gestures that accompany speech, and she is telling me all this by phone. Since I don't have a videophone, the gestures can't be for my benefit.

That may not surprise those of you who lose the power of speech if your hands are immobilized. But the function of waving, flapping or otherwise moving your hands while you talk is only now becoming clear, as Prof. Goldin-Meadow recounts in her new book, "Hearing Gesture: How Our Hands Help Us Think," published by Harvard University Press. Gesture, she concludes, "plays an active role in … the thoughts we think."

One strong hint that gesture isn't merely decorative comes from its strange ubiquity. In every known culture speakers move their hands. More interesting, people who have been blind from birth -- and so have never seen a gesture -- wave their hands while speaking, as do both sighted and blind people when conversing with the blind or on the phone.

Gesture, as close to a universal of human behavior as you can get, is as much for the benefit of the speaker as for the listener. 

It's as if the hands reveal even "information you may not know you have," says Prof. Goldin-Meadow. "Gesturing is a way to take your thoughts and put them out there for you and others to see. It may help you examine your thoughts, even if not consciously."

Studies of gesture were pioneered by University of Chicago linguist David McNeill, who concluded that speech and gesture are two aspects of a single linguistic system. Indeed, there are many hints that the greater the cognitive effort required for speech, the more we gesture. Hands typically go into overdrive when speakers hear their own words played back while they continue talking (that's called delayed auditory feedback -- or a bad international connection), and also when bilinguals speak the language in which they are weaker. We also gesture more when describing a picture from memory than we do when it is in plain sight. 

And the point of all that hand-waving? Gesturing seems to decrease "cognitive load," the amount of mental effort needed to perform some task. In one series of studies, volunteers listened to a set of definitions and had to provide the word being defined. Those who were told to keep their hands in the pocket of an apron came up with fewer words than people whose hands were free and gesturing. This study was a bit ambiguous, though, since most people who found the right words did so before they gestured.

To test whether gesturing literally takes a load off your mind, Prof. Goldin-Meadow and her colleagues had volunteers solve math problems, such as factoring the expression x2 -- 3x -- 10. Once the volunteers had done so (the factors are x -- 5 and x + 2), they were given a double task: Memorize a long list of random letters while explaining how they did the math. 

The adults who gestured at will while explaining their factoring remembered more of the letters than did volunteers who weren't permitted to gesture. 

Gesturing, then, seems to off-load some of the mental effort needed to explain math, freeing up more cognitive resources for recall. How it does so is an open question. "But at the very least," says Prof. Goldin-Meadow, "we ought to stop telling people not to move their hands when they talk."

Oh, and that stereotype about Italian-speakers? They do make larger, more expansive gestures than English speakers, but not more of them. 

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