The phenomenon of generativity is one piece of evidence against the theory that language is acquired via principles of learning. what does generativity refer to?

Children compose sentences they have never heard before.

Explanation:

Generative Language can be defined as an innate ability to compose and understand sentences that have never been heard or said before. This principle of Generative Language or Generative Grammar was theorized by Noam Chomsky in 1957 in his book titled "Syntactic Structures."

He theorized that people are born with an innate ability to understand and acquire their native language. Chomsky believed that children are born with this innate language potentiality that further needs to be polished by learning words.

He named this innate ability to acquire language 'universal grammar' which suggests that humans are born wired with the ability to understand and compose the language.

Thus generativity refers that children can form sentences that they have never heard before.