Learning theorists' claim that language is learned strictly through imitation and reinforcement has been challenged by other theorists who propose that an inborn mechanism helps children learn grammar

Give an example of a language phenomenon that learning theory has difficulty explaining and describe evidence that supports the notion of an inborn grammar-learning device.
What will be an ideal response?

A good answer will be similar to the following:
- One problem for learning theorists is how to explain the fact that children produce novel sentences and grammar — sentences that are not simply imitations of sentences they've heard earlier.
- According to the semantic bootstrapping theory, children are born knowing that nouns usually refer to people or objects, and that verbs are actions. They use this knowledge to infer grammatical rules.
- Evidence supporting the notion of an inborn language-learning device:
+ Specific regions of the brain are known to be involved in language processing. The fact that specific areas in the brain have well-defined functions for language make it plausible that children have specialized neural circuits that help them learn grammar.
+ Only humans learn grammar readily. If grammar is learned solely through imitation and reinforcement, then it should be possible to teach rudimentary grammar to nonhumans. Efforts to teach grammar to chimpanzees have failed, suggesting that children rely upon some type of inborn mechanism to master grammar.
+ There is a critical period for learning language, based on cases of isolated children and from studies of individuals learning second languages. The period from birth to about age 12 is critical for acquiring language and mastering grammar, suggesting that the neural mechanisms involved in learning grammar may function only during infancy and childhood.
+ The development of grammar is tied to the development of vocabulary. The mastery of grammar is closely related to vocabulary growth, in a way that suggests both are part of a common, emerging language system. The tight coupling of vocabulary and grammar in adopted and bilingual child goes well with the idea that the development of vocabulary is regulated by a common, language-specific system.