What is Poverty of Stimulus?

Poverty of stimulus 

Poverty of stimulus is a key concept in Chomsky’s theory of UG. According to him human brain is pre-programmed with some LADS, which make it possible to learn a language. Contrary to the environmentalist theory of language acquisition, Chomsky puts forward the argument that it is impossible for the humans to learn a language only on the basis of the linguistic data  that they derive from outside. He termed this as ‘poverty of the stimulus’. According to him the stimulus or the linguistic data are insufficiently rich to make the language learning possible. He said that the stimulus is poor in mainly two ways. At, first they lack the negative evidence. Secondly, they are marred by the performance features.