Many of us are crazy about money. We spend too much of it and save too little. We hoard it and we sink into debt over it. We lavish it and are stingy with it. We lie about it and fight over it. We think about it all the time and we avoid thinking about it at all. What makes us act this way? We like to believe that our choices and actions are guided by rationality and common sense. But in fact, reason and common sense often have little to do with our...