Final answer:
In Stewart and Healy's model, a major historical event during adolescence is likely to have a significant impact on the psychological and social changes that occur during this stage of development, shaping adolescents' identity and values.
Step-by-step explanation:
In Stewart and Healy's model, historical events have a different impact depending on the period of development during which they occur. According to this theory, when a major historical event takes place during adolescence, it is likely to have a significant impact on the psychological and social changes that occur during this stage of development. Adolescents are already experiencing a strong desire to conform to their peer group, and a major historical event can further shape their identity and values based on the reactions and influences of their peers. For example, if a major historical event promotes social activism, adolescents may become more politically engaged and passionate about certain causes. On the other hand, they may also become more conformist and adopt the dominant beliefs and values of their peer group in response to the event.