Some surprising results have emerged from our research. We leamed that leaders need all four qualities to be truly inspirational; one or two qualities are rarely sufficient. Leaders who shamelessly promote their differences but who conceal their weaknesses, for instance, are usually ineffective-nobody wants a perfect leader. We also learned that the interplay between the four qualities is critical. Inspirational leaders tend to mix and match the qualities in order to find the right style for the right moment. Consider humor, which can be very effective as a difference. Used properly, humor can communicate a leader's charisma. But when a leader's sensing skills are not working, timing can be off and inappropriate humor can make someone seem like a joker or, worse, a fool. Clearly, in this case, being an effective leader means knowing what difference to use and when. And that's no mean feat, especially when the end result must be authenticity.