The earliest theories of language were initially based on the “nonsense” idea that imitation is
how children learn a language. It does play a part, but only a small one. Toddlers who copy the way adults speak are the ones who show the most rapid vocabulary development, but only in the first 1/2 years of the language explosion. It doesn’t account for all language acquisition, therefore we cannot say that this is the way children learn. It also doesn’t add up, as it cannot possibly account for a child’s ability to create new words and expressions which they have never heard before.

Skinner’s (1957) reinforcement there argues that parents play a bigger role than just imitation. They are vital in the process of shaping language, gradually improving a child’s speech. However, researchers have found that when parents speak to children, there is no evidence of this shaping, making this a very controversial theory. In contrast to this, (Brown & Hanlon, 1970; Hirsh-Pasek, Trieman, & Schneiderman, 1984), found that parents actually construct children vocabulary in a range of different ways. The most common, when they correct them on the basis of whether they are correct or not.

Developmentalists can tell which children have parents who talk and read to them often, as they use a wider range of vocabulary in their speech. They also tend to begin talking sooner, and developing larger vocabularies quicker. This makes it evident that a child who hears a larger quantity of language is more likely to benefit in this way. Children who don’t hear such a large quantity of language in their early years don’t even appear to catch up in their later years.It has also been found by the Peabody Picture Vocabulary Test, that poor mothers talk and read to their children less and also use much poorer vocabulary and complex sentences. Catherine Snow (1997) found that children at four years of age brought up in poverty, use shorter/less complex sentences than their better-off peers. Obviously there are other contributing factors, but the variety of language a child hears is fundamental in their language development.

Motherese, is the simple language adults use to talk to children. It is now referred to as infant-directed speech. This is done so in a higher-pitched voice and also at a much slower pace. It is believed that babies can tell the difference between people speaking in infant-directed speech and normal speech as early as a few days old. Developmentalists have also found that they prefer to be spoken to in motherese. They like the higher pitch as it catches their attention. 

There are a few issues with the theory of language acquisition. Children who hear their own sentence repeated back to them grammatically correct will learn correct grammar sooner, but recastings are actually really rare (and children still acquire complex grammar eventually. Also, mothers do appear in a range of countries and cultures, it is not evident in all. (Better, 1988) also found that motherese is not used very much by mothers suffering from depression. These children still learn the language and grammar, proving that whilst infant-directed speech does play an important role, it is not always necessary.

Nativist Theorists argue that all a child needs to learn language is already within them. Early theorists such as Noam Chomsky were interested in the size of the task of acquiring language, and the similarities in the stages of language development across every language. Another influential nativist is Dan Slobin. He stated that every child is born already having a basic language-making capacity. 

The Nativist Theory is discussed very well in this YouTube video:

Constructivist Theorists state that built-in perceptual skills are very important in acquiring language. These build skills guide her attention to specific features of language which she then processes and modifies as and when she receives new information. By doing this, the child develops their own set of rules for both understanding and creating language.

The Eclectic Approach is where theorists draw on all the views of language acquisition, to gain a greater understanding on the environments influences. It is especially important to use both the nativist and cognitive theories. This is as the nativists claim that the ability to process to language is already processed in a child’s brain. This claim is best understood when looked at from a constructivist view of language development. 

All these theories are interesting and many have similar ideas, but it is interesting to see the different ideas from different psychologists.