According to Lev Vygotsky :

CONCEPT: Lev Vygotsky's sociocultural theory holds that higher mental functions originate in social interaction and are mediated by language. Language is not merely an expression of already-formed thought; it functions as a psychological tool that a child first uses in social, spoken form and gradually internalizes as inner speech, and this internalized language becomes the vehicle for reasoning, planning, and other higher-order thinking.

APPLICATION: Vygotsky's key claim about the relationship between language and cognition is directional: language development drives cognitive development, not the reverse. As a child's linguistic ability grows through social interaction, that language is internalized and reorganizes the child's thinking, producing more advanced cognitive functioning. This is the reverse of Piaget's position, where cognitive maturity is treated as a precondition for language use. Matched against the given options, the option stating that language development facilitates cognitive development directly reflects this internalization-driven direction.

CROSS-CHECK: Comparing each option's claim against this account -

• Social factors influence language development, but not cognitive development: narrows social influence to language alone, whereas Vygotsky treats social interaction as the origin of cognitive growth as well, through language.

• Cognitive development facilitates language development: reverses the direction Vygotsky proposed; this ordering is closer to a cognition-first account than to sociocultural theory.

• Language development and cognitive development advance independent from each other: contradicts the central sociocultural claim that the two are interlinked through internalized speech.

• Language development facilitates cognitive development: matches Vygotsky's account - internalized social speech becomes the tool of thought, so language growth drives cognitive growth.