Read Without a Net--Daniel B. Smith's review of Balance: In Search of the Lost Sense by Scott McCredie (Little, Brown & Company)--in The New York Times Book Review, August 19, 2007.
Smith writes, "Balance is a 'multimodal' faculty...perhaps best thought of as the sum total of other senses." He quotes McCredie: "The act of balancing a mass as large as a human body over a base as small as two human feet is exceptionally demanding. It's roughly equivalent to trying to balance a triangular object over one of its points; the natural tendency is for gravity to push it over."