Final answer:
The characteristic that distinguishes the adolescent's self-concept from that of a child is complexity, as adolescents explore and refine their identities during their developmental stage according to Erikson's theory.
Step-by-step explanation:
One of the characteristics that distinguish between the adolescent's and the child's self-concept is complexity. During adolescence, individuals undergo a significant transformation in their self-concept as they grapple with identity versus role confusion. According to Erikson's theory of psychosocial development, the main task of an adolescent is developing a sense of self, which involves exploring different identities and roles to determine who they are and what they want out of life. As adolescents refine their sense of self, their self-concept becomes more intricate and multifaceted, compared to the typically simpler self-concept observed in children.