Another issue in the study of eating disorders is that, unlike many other disorders, they emerge almost exclusively during adolescence and young adulthood. Adolescence is a time of identity formation (Erikson, 1958) and according to Wilson, Heffernan, and Black (1996), girls are more concerned than boys with how others perceive them. So, those whose identity is insecure may choose physical appearance as a way to construct identity. Since the physical maturation that occurs at adolescence causes girls to gain weight, those who are insecure in their identity might choose weight loss as a means to gain the acceptance of others in an effort to construct their identity. A longitudinal study by Attie and Brooks-Gunn (1989) looked at eating problems in adolescent girls. Although they investigated a number of factors, their findings are most noteworthy in what they show about girls' acceptance of their own physical changes of the pubertal period. Subjects were 193 Caucasian girls in grades 7, 8, 9, and 10. They were also assessed two years later. Questionnaires were administered to the girls at Time 1, and to the girls and their mothers at Time 2. The authors found that the accumulation of body fat, which is part of female maturation, may elicit the initiation of dieting. Furthermore, a negative body image at Time 1 was a predictor of problem eating behaviors at Time 2. The study is useful for showing the importance of weight gain and negative body image-two factors that are unique to adolescence-as predictors of the development of eating disorders.