Different influences on child language development have been studied and theorised over; some argue that language acquisition and development are cognitive, and language learning is an innate process, yet others express the importance of interaction with a more knowledgeable other. To place one influence above the many others is ambitious, especially when context is so important.

Interaction provides children with the opportunity to engage and build conversational communication skills, which is an important aspect of language development. In the data set, Joey is in Piaget’s preoperational stage of cognitive development, meaning he is developing symbolic thinking and is engaging in pretend play. Examples of this are seen when Joey places Lego pieces into the saucepan and claims they are eggs, and when he picks up an old dictionary, calling it a “cooker book”. This imaginative use of language, according to Halliday's functions of language theory, is beneficial as it develops communication skills when conversing with caregivers in a new imaginary scenario, as in the data set where Joes is cooking eggs, he is using his cognitive knowledge to state his intention: “have to put milk in and then mix it up”, this reflects a semantic understanding of the method to cook eggs, using relevant terminology such as the dynamic verb “mix”. Moreover, Joey is supported by the adult caregiver, who acts as a support system for Joey, as the caregiver repeatedly asks supporting questions such as “does it”, “are you” and copies Joey in stressing the dynamic verb “breaks”. This helps to scaffold learning by matching the child’s developmental stage and mirrors their communication to encourage the conversation onwards, teaching correct language structures without overt correction. This emphasises the importance of caregiver interaction on the development of a child’s language and heavily suggests that language develops through social context and collaboration, yet the over-generalisation of “cooker” rather than “cookery” and “saucy” rather than “sauce” implies a more internalised influence on language development as these structures wouldn’t have been heard before by Joey, he is simply applying preconceived structures to sentences which also stresses the importance of acknowledging cognitive development in language development.

Cognitive understanding and development play a key role in language acquisition. The virtuous errors “cooker” and “saucy” made by Joey suggest that children have an in-built language acquisition device and that not all language is learnt through imitation and interaction with caregivers. This is furthered by the “crawns” mistake made by Joey, to which the adult attempted to correct with negative reinforcement, but Joey didn’t understand his own mistake, exactly like Berko and Brown’s fis phenomenon, which shows that perception precedes production, and that cognitive understanding develops faster than articulation. These findings support Chomsky's nativist theory, which emphasises nature over nurture. However, this theory conflicts with the Genie case study, which shows us that cognitivism does hold an influence but only to a certain extent, as without human interaction and the social process of language learning, language acquisition cannot be fully completed. The social processes shown within the case study, where language is used by Joey for a variety of functions (imaginative, regulatory and interactional), reflect the importance of social processes within language acquisition. Although this doesn’t entirely mean that cognitivism isn’t important as it clearly plays a key role, as seen in Papa New Guinea’s upbringing culture where no LASS, scaffolding or reinforcement is given to the children, yet they develop their language at roughly the same time as children who do experience these aids, proving that cognitivism is an important influence on a child’s language development.

To conclude, it is ambitious and narrow-minded to select one single “most important” influence on language acquisition and development. Interaction strengthens connections and builds upon communication skills and cognitive thinking when in imaginary play scenarios. It emphasises the importance of the social processes endured and the context of the child’s upbringing, yet it all comes together through the cognitive processes within the child’s mind, so both hold an equally important influence on a child’s language development.