Like most bureaucrats, Robert Groves, the director of the U.S. Census Bureau, has cultivated a poker face that works pretty well when he's fending off irksome questions from congressmen about why he spent $2.5 million on a TV ad during the Super Bowl or $3 million training employees who were fired before they worked a single day. But through careful observation of Groves' body language, it's possible for trained observers to interpret his words. When he scratches his right ear, for instance, he's telling the truth. When he cups his chin in his hand or rests a finger on his...