Over the last fifty years, several theories have been put forward to explain the process by which children learn to understand and speak a language. They can be summarized as follows:
Theory
Central Idea
Individual most often associated with theory
Behaviourist
Children imitate adults. Their correct utterances are reinforced when they get what they want or are praised.
Skinner
Innateness
A child's brain contains special language-learning mechanisms at birth.
Chomsky
Cognitive
Language is just one aspect of a child's overall intellectual development.
Piaget
Behaviourism
The behaviourist psychologists developed their theories while carrying out a series of experiments on animals. They observed that rats or birds, for example, could be taught to perform various tasks by encouraging habit-forming. Researchers rewarded desirable behaviour. This was known as positive reinforcement. Undesirable behaviour was punished or simply not rewarded - negative reinforcement.
Skinner suggested that a child imitates the language of its parents or cares. Successful attempts are rewarded because an adult who recognizes a word spoken by a child will praise the child and/or give it what it is asking for. Successful utterances are therefore reinforced while unsuccessful ones are forgotten.
Limitations of Behaviourism
While there must be some truth in Skinner's explanation, there are many objections to it.
Language is based on a set of structures or rules, which could not be worked out simply by imitating individual utterances. The mistakes made by children reveal that they are not simply imitating but actively working out and applying rules.
Children are often unable to repeat what an adult says, especially if the adult utterance contains a structure the child has not yet started to use. The classic demonstration comes from the American psycholinguist David McNeill. The structure in question here involves negating verbs:
Child: Nobody