Final answer:
Lev Vygotsky's sociocultural theory of development suggests that social interaction and cultural norms are fundamental to cognitive and language development. Speech starts as external communication and becomes internalized as inner speech, which is crucial for thought organization and planning.
Step-by-step explanation:
Lev Vygotsky, a Russian psychologist, presented a sociocultural theory of development which posits that social interaction plays a fundamental role in the development of cognition. Vygotsky believed that our ability to learn language is deeply rooted in social interactions and cultural norms. He emphasized the importance of cultural tools in cognitive development, including language, and described how social interaction leads to continuous step-by-step changes in children's thought and behavior.
Vygotsky differentiated between two forms of speech: external and internal. External speech is the speech we verbalize to others—it is how children initially communicate with the world around them. Over time, this external speech becomes internalized as inner speech. Inner speech is a form of internal dialogue that we have with ourselves; it is an essential part of how we organize our thoughts and plan our actions. Moreover, Vygotsky’s theory suggests that language development influences thought and cognitive development, which is a dynamic process fostered by social interaction and cultural tools.