Describe one criticism researchers have of the behaviorist and nativist theories of language development.

One criticism of the behaviorist theory is that it doesn't explain why children often use language in a way that is not portrayed by adults. For example, children often use processes like overregularization, which is not mimicked from watching adults, so it isn't logical to claim that children learn language through imitation. One criticism of the nativist theory is that the process of the language acquisition device (LAD) is vague. Nativist theorists fail to explain how the process really works.

The behaviorist theory of language acquisition, first introduced by Skinner in 1957 stated that children learn a language by the reinforcement they get from the environment. For example, if a child says "water" and the mother gived him/her a glass of water, that is taken as a positive outcome enhacning the child's language development.

Skinner was criticzed by Chomsky (1950) and his theory of Universal Grammar. He argued that children will never acquire the tools needed for porcessing sentences if the system of acquisition is only dependant on language input. Instead, he proposed the idea of innate, biological grammatical categories (such as verb or noun categories) and children instinctively know how to use them. This Nativist theory was criticized by some researchers who suggest that instead of having a language processing mechanism, children might use general cognitive and learning principles for language processing. They favor a more gradual pattern of language learning such as morphology acquisition: after listening for many times the same pattern (for example "a dog barkS"), the child will detect the pattern of the sentences and incorporate it.