Lev Vygotsky, the famous Russian psychologist, adds two elements in his theory of cognitive development.
He stresses the impact of culture and language on the cognitive development. According to him, without culture, our intellectual functioning is limited to apelike, elementary mental functions.
In his words, intensive interaction with the elements of culture and a healthy language development, we become capable of higher mental functions involved in thinking, reasoning, remembering and so on.

Key PointsFurther Vygotsky states that a child progresses through three stages in developing language functions: i.
1) Social (External) Speech (before age 3 or 4 years)
It is used largely to control others or to express simple concepts.
2) Egocentric Speech (3 – 7 years)
It is mostly talking about self and is usually spoken out loud. It has a role in controlling and directing the child’s own behaviour
3) Inner Speech (above 7 years)
It is marked by unspoken verbalizations that control thought and behaviour. Vygotsky argues strongly for language related activities in schools and inclusion of cultural elements in the curricular interactions in and outside of the classroom
Hence, it could be concluded that I, II and III are correct.

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