Final answer:
Erik Erikson is the theorist who placed the most emphasis on identity formation during adolescence, particularly in his fifth stage of psychosocial development, identity versus role confusion.
Step-by-step explanation:
The theorist who placed the most emphasis on the quest for identity in adolescence is Erik Erikson. Erikson's stage theory of psychosocial development, specifically the fifth stage, identity versus role confusion, is centered on the development of a personal identity during adolescence. Erikson believed that adolescents needed to explore different aspects of themselves through various roles and experiences. Those who successfully navigate this period develop a strong sense of identity, whereas those who do not may experience uncertainty and confusion about their place in the world.
Erikson's focus on social relationships and their impact on personality development differs from Freud's theory, which was more focused on internal psychic conflicts. Erikson broadened the scope of developmental stages to encompass a lifespan perspective where the outcomes of each stage influence subsequent stages. Therefore, the success or failure to develop a firm sense of identity in adolescence has profound implications for future stages, such as forming intimate relationships in young adulthood.