The French Impressionists were students of gesture, the author says. In this famous work by Renoir, three different love triangles can be seen, all told through body language, he says. (Credit: Pierre-Auguste Renoir [1841-1919], Luncheon of the Boating Party, 1881, oil on canvas, 51 1/4 x 69 1/8 inches. Acquired 1923, The Phillips Collection, Washington, D.C.)