<P> Language transfer often occurs when learners sense a similarity between a feature of a language they already know and a feature of the interlanguage they have developed . If this happens, the acquisition of more complicated language forms may be delayed in favor of simpler language forms that resemble those of the language the learner is familiar with . Learners may also decline to use some language forms at all if they are perceived as being too distant from their first language . </P> <P> Language transfer has been the subject of several studies, and many aspects of it remain unexplained . Various hypotheses have been proposed to explain language transfer, but there is no single widely accepted explanation of why it occurs . </P> <P> The primary factor affecting language acquisition appears to be the input that the learner receives . Stephen Krashen took a very strong position on the importance of input, asserting that comprehensible input is all that is necessary for second - language acquisition . Krashen pointed to studies showing that the length of time a person stays in a foreign country is closely linked with his level of language acquisition . Further evidence for input comes from studies on reading: large amounts of free voluntary reading have a significant positive effect on learners' vocabulary, grammar, and writing . Input is also the mechanism by which people learn languages according to the universal grammar model . </P> <P> The type of input may also be important . One tenet of Krashen's theory is that input should not be grammatically sequenced . He claims that such sequencing, as found in language classrooms where lessons involve practicing a "structure of the day", is not necessary, and may even be harmful . </P>

What are the goals of second language acquisition