<P> The path--goal theory, also known as the path--goal theory of leader effectiveness or the path--goal model, is a leadership theory developed by Robert House, an Ohio State University graduate, in 1971 and revised in 1996 . The theory states that a leader's behavior is contingent to the satisfaction, motivation and performance of his or her subordinates . The revised version also argues that the leader engages in behaviors that complement subordinate's abilities and compensate for deficiencies . According to Robert House and John Antonakis, the task - oriented elements of the path--goal model can be classified as a form of instrumental leadership . </P> <P> The first theory was inspired by the work of Martin G. Evans (1970), in which the leadership behaviors and the follower perceptions of the degree to which following a particular behavior (path) will lead to a particular outcome (goal). The path--goal theory was also influenced by the expectancy theory of motivation developed by Victor Vroom in 1964 . Vroom built his work on the work of Georgopoulos et al. (1957): A path - goal approach to productivity . Journal of Applied Psychology . Volume 41, No. 6, pages 345--353 . </P>

What is the main principle of path-goal theory