" the skills possessed by a designated leader or the holder of an office may make him well-qualified to perform important group functions under certain conditions and poorly qualified under others…. The specific requirements of the group’s tasks demand that members possess certain skills in order to serve the appropriate functions. If the task changes, different behaviors are required, and the same person may or may not be able to perform in the new way. "

― Walter Isaacson , Profiles in Leadership: Historians on the Elusive Quality of Greatness