Language has 5 major properties:

Infants vocalise from the moment they are born — deaf infants vocalise and babble in the same way that hearing infants do (Lenneberg, 1967).

Early language development involves turn taking — children become socialised linguistically.

Adults help children to learn language through the use of ‘Motherese’ (Newport, Gleitman and Gleitman, 1977). Motherese is characterised by a special tone of voice that exaggerates the sounds

Most children begin talking in one word sentences at about one year of age. At about the age of two, children use telegraphic speech — putting together two words, but without any functional grammatical structure.

Language learning takes place successfully in many radically different environments. It only fails in cases where children are not raised in human company, feral children.

Children who are isolated from learning around them, invent some of it for themselves. Deaf children will make pantomime-like gestures in order to be understood.

In children with brain abnormalities or with deficits, there is a marked alteration of ability to learn language.

Because experimental evidence shows that language learning is based on special properties of the human brain, it seems that we should not expect other higher order animals such as chimpanzees and dolphins to be able to learn language in the same way. However it seems that chimpanzees have a good capacity to learn words to the level of a 30 month old child. But they have not demonstrated the ability to use grammatical structure.

Language learning therefore results from the interaction between a young human brain and various social and cognitive experiences provided within a given environment. It could be argued that language is what makes us uniquely human.