A study found that it is really efficient.
A team of researchers from the University of Minnesota studied the behavior of a group of children between the ages of four and six on concentration on school tasks. The study brought together a group of 180 children ages four to six and were assigned a rather boring computer task.
They were divided into three groups, the children in group 1 were asked to work on their task, concentrating fully on it, and to continually ask themselves “Am I working hard?” Children in group 2 were asked the same but identifying with an imaginary person they called Hannah, and they were invited to ask the question, “Is Hannah working hard?” and children in group 3 were asked to dress up as the fictional character of their choice and to really think that he was working hard.
The results of group 2, which identified with an imaginary third person, were significantly better than those of group 1, who were asked to be themselves, but those of group 3 were those who presented greater effort and concentration. So they concluded that the costumed children identified with the character traits of the superhero or character they wanted to imitate.