Functional leadership theory is a theory for addressing specific leader behaviours expected to contribute to organizational or unit effectiveness. This theory argues that the leader's main job is to see that whatever is necessary to group needs is taken care of; thus, a leader can be said to have donetheir job well when they have contributed to group effectiveness and cohesion. Functional theories of leadership are developed by studying successful leaders and identifying the actions and behaviours they show. Large studies with a large amount of data make it possible to correlate what leaders actually do, i.e. their actions or functions with their successful results. In the functional leadership model, leadership does not rest with one person but rests on a set of behaviours by the group that gets things done. Any member of the group can perform these behaviours, so any member can participate in leadership. The Functional theory of leadership, places greater emphasis on how an organisation or task is being led rather than who has been formally assigned a leadership role. One of the best known and most influential of functional theories of leadership, used in many leadership development programmes, is John Adair's "Action-Centred Leadership". John Adair developed a model of Action-Centred Leadership that has connecting circles that overlap because:
the task can only be performed by the team and not by one person
the team can only achieve excellent task performance if all the individuals are fully developed
the individuals need the task to be challenged and motivated
Adair's model challenged trait theory by focusing on what leaders do. He showed that leadership could be taught and did not depend on the traits a person had.
This question of whether leaders are born or made is part of the whole question of whether human behaviour is due to nature or nurture. It is a short leap from functional leadership theory, to the belief that if one person can do something, then others can also learn to do it. The implication that leaders are made and not necessarily born with the necessary traits for leadership, opened up the possibility of leadership development.