The question; "what is learning?" seems simple enough. However, philosophically it is a very hard question to "answer", and this is why it has been a challenging topic for philosophers for centuries. The schools of thought on the nature of learning have been many and varied, but at the most basic level they differ on only a limited number of fundamental questions. These are questions like; "How does learning occur?", "What are the properties of knowledge? (absolute, relativistic..)" etc..

A great many theories regarding language development in human beings have been proposed in the past and still being proposed in the present time. Such theories have generally arisen out of major disciplines such as psychology and linguistics. Psychological and linguistic thinking have profoundly influenced one another and the outcome of language acquisition theories alike. This article aims to discuss language acquisition theories and assess their implications for applied linguistics and for a possible theory of foreign/second language teaching.

Language acquisition theories have basically cantered around “nurture” and “nature” distinction or on “empiricism” and “nativism”.

The doctrine of empiricism holds that all knowledge comes from experience, ultimately from our interaction with the environment through our reasoning or senses. Empiricism, in this sense, can be contrasted to nativism, which holds that at least some knowledge is not acquired through interaction with the environment, but is genetically transmitted and innate. To put it another way, some theoreticians have based their theories on environmental factors while others believed that it is the innate factors that determine the acquisition of language. It is, however, important to note that neither nurturists (environmentalists) disagree thoroughly with the nativist ideas nor do nativists with the nurturist ideas. Only the weight they lay on the environmental and innate factors is relatively little or more. Before sifting through language acquisition theories here, therefore, making a distinction between these two types of perspectives will be beneficial for a better understanding of various language acquisition theories and their implications for the field of applied linguistics. In the following paragraphs, the two claims posed by the proponents of the two separate doctrines will be explained and the reason why such a distinction has been made in this article will be clarified.

Environmentalist theories of language acquisition hold that an organism’s nurture, or experience, are of more significance to development than its nature or inborn contributions. Yet they do not completely reject the innate factors. Behaviourist and neo-behaviourist stimulus-response learning theories (S-R for simplicity) are the best known examples. Even though such theories have lost their effect partially because of Chomsky’s intelligent review of Skinner’s Verbal Behaviour (Chomsky, 1959), their effect has not been so little when we consider the present cognitive approach as an offshoot of behaviourism.

The nativist theories, on the other hand, assert that much of the capacity for language learning in human is ‘innate’. It is part of the genetic makeup of human species and is nearly independent of any particular experience which may occur after birth. Thus, the nativists claim that language acquisition is innately determined and that we are born with a built-in device which predisposes us to acquire language. This mechanism predisposes us to a systematic perception of language around us. Eric Lenneberg (cited in Brown, 1987:19), in his attempt to explain language development in the child, assumed that language is a species - specific behaviour and it is ‘biologically determined’. Another important point as regards the innatist account is that nativists do not deny the importance of environmental stimuli, but they say language acquisition cannot be accounted for on the basis of environmental factors only. There must be some innate guide to achieve this end.

It has often been noticed that, whereas just about everyone learns a first language with great ease, very few people manage to learn a second language so well that they can pass for a native. Moreover, while there is very little variation in final competence in L1, people vary widely in the extent to which they acquire an L2. One of the first questions that we should ask, then, is whether there is any relationship between the acquisition of an L1 and the acquisition of an L2?