When we think of great leaders, those that come to mind first -- say, Jack Welch, Steve Jobs, or Martin Luther King, Jr. -- tend to be charismatic, larger-than-life figures. Such examples have led to the popular belief, particularly in business, that extroverts have an advantage in their careers. Those who are outgoing, unafraid of the spotlight, and speak their minds and give direction are natural leaders, the conventional thinking goes. While this isn't necessarily wrong, nor is it the whole story, according to researchers from the University of Pennsylvania's Wharton School, Harvard Business School, and the University of North Carolina's Kenan-Flagler Business School. Introverts can be equally effective leaders, says Wharton's Adam Grant, lead author of "Reversing the Extraverted Leadership Advantage: The Role of Employee Proactivity" in a forthcoming issue of the Academy of Management Journal. Interestingly, Grant and his colleagues find, neither extraverts nor introverts perform better in productivity or profits. Instead, the real indicator of success lies in the pairing of each type of leader with different types of employees.