Never mind what's on display at the average office party or college mixer: humans have an innate ability to dance. Even toddlers spontaneously jump and sway in time to music that they like. Dance is roughly universal among the world's cultures and is often invested with great, even sacred, significance; the exceptions seem to be societies where dance was expressly forbidden because its influence was deemed too powerful.

Our terpsichorean facility appears to be an extension of our general affinity for music, which is already an evolutionary puzzle: Why do we have such advanced musical appreciation when it lacks any obvious direct survival value? But at least nature has precedents among songbirds and other creatures that respond to music. As Steven Brown and Lawrence M. Parsons note in their article about " The Neuroscience of Dance " (page 78), our propensity to link rhythmic movements to music is apparently unique. Humans are not merely the Fred Astaires of the animal kingdom: they are the only ones on the ballroom floor.

Always graceful, Astaire made dancing look easy (as did Ginger Rogers, who paralleled every step backward and in heels). The reality is that moving our bodies precisely, rhythmically and expressively through space while coping with gravity and balance is a highly demanding challenge. Yet even if few of us can rival the success of professional dancers at the feat, it is roughly within our natural capacities. The neural circuitry involved extends from deep within the brain stem to the cortex, as Brown and Parsons have learned by scanning the brains of dancers in the act. Read their article for details of how they peeked inside dancers' heads and be sure to look at the pictures immortalizing what is probably the first tango ever performed in a PET scanner.

One intriguing detail of their discoveries suggests that the right hemisphere's anatomical counterpart to one speech center becomes active during interpretive dance. Admirers of the art often talk about the "language of dance," and the scientists' work suggests that this may be more than a metaphor. Perhaps movement constituted a form of language, or at least nuanced communication, long before our ancestors ever spoke aloud. Society has been slow to accept it, but the deaf community has made a similar point for decades in its fight to have signing recognized as a legitimate language.

Surely among the clearest and most direct ways for us humans to communicate with one another are gestures. Our machines, in contrast, have been obtuse to them. One robust area of current interface research concerns helping computers to interpret gestures, and a practical application emerging from one corner of that work has been the development of "multi-touch" screens for phones and other devices. Users can shrink, enlarge, rotate or otherwise manipulate images with pinches, flips and other intuitive movements of the fingers against the screen. The beauty of the systems is that working with them is so natural—but years of hard innovation went into their development. Journalist Stuart F. Brown (no relation to Steven!) describes how these devices work, starting on page 64.

Note: This story was originally printed with the title, "Minds in Motion".

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