Final answer:
The sociocultural theory of development, proposed by Lev Vygotsky, explains that an individual's development and future success are deeply influenced by social experiences and cultural background.
Step-by-step explanation:
The theory that focuses on how social experiences and culture affect an individual's development and future success is known as the sociocultural theory of development, which was proposed by Russian psychologist Lev Vygotsky. This theory emphasizes that human development, including the formation of language and thought, is fundamentally rooted in one's social and cultural environment. Elements such as social interaction, the language one speaks, and the cultural background all play critical roles in an individual's development. Vygotsky also believed that historical influences are key to understanding developmental processes and how individuals interact with their surroundings.