[填空题]According to sociologists, there are several different ways a person may become recognised as the leader of a social group. Although leaders are often thought to be people with unusual personal ability, decades of research have failed to produce (36) evidence that there is any category of "natural leaders". It seems that there is no set of personal qualities that all leaders have in common; rather, (37) any person may be recognised as a leader if the person has qualities that meet the needs of that particular group.
Research suggests that there are typically two different leadership roles that are held by different individuals. Instrumental leadership is leadership that (38) the completion of tasks by a social group. Group members look to instrumental leaders to "get things done". Expressive leadership, on the other hand, is leadership that emphasises the collective well-beings (幸福) of social group members. They are less (39) with the