The star-spangled grin Study found that women with big, warm smiles at age 21 had happier, more productive lives DEBRA BLACK STAFF REPORTER Be it Leonardo da Vinci's Mona Lisa and her mysterious smile, or Lewis Carroll's grinning Cheshire cat, a smile can not only light up a room, but can also reveal nationality and radiate sexual appeal, warmth, modesty and decorum, according to an American researcher. For example, Americans and the British have two quite distinct smiles, said Dacher Keltner, a psychology professor at the University of California at Berkeley who has studied the mysterious art of smiling. An...