We take it for granted today that babies need love. But less than a century ago, psychologists warned women against showing their children "too much affection"-predicting dire consequences ranging from deadly disease to sexual dysfunction in adulthood. The story of how this conventional wisdom was finally shattered takes us into the life and the laboratory of Harry Harlow-workaholic, alcoholic, brilliant and brave, capable of caustic wit and cruelty-and into an era in which the scientific establishment was just beginning to understand the power of human emotion.