THE INPUT HYPOTHESIS
(a) Statement of the hypothesis
Let us first restate the question of how we acquire: given the correctness of the natural
order hypothesis, how do we move from one stage to another? If an acquirer is at
"stage 4", how can he progress to "stage 5"? More generally, how do we move from
stage i, where i represents current competence, to i + 1, the next level? The input
hypothesis makes the following claim: a necessary (but not sufficient) condition to move
from stage i to stage i + 1 is that the acquirer understand input that contains i + 1, where
"understand" means that the acquirer is focused on the meaning and not the form of the
message.
We acquire, in other words, only when we understand language that contains structure
that is " a little beyond" where we are now. How is this possible? How can we
understand language that contains structures that we have not yet acquired? The
answer to this apparent paradox is that we use more than our linguistic competence to
help us understand. We also use context, or knowledge of the world, our extra-linguistic
information to help us understand language directed at us.
The input hypothesis runs counter to our usual pedagogical approach in second and
foreign language teaching. As Hatch (1978a) has pointed out, our assumption has been
that we first learn structures, then practice using them in communication, and this is how
fluency develops. The input hypothesis says the opposite. It says we acquire by "going
for meaning" first, and as a result, we acquire structure! (For discussion of first language
acquisition, see MacNamara, 1972).
We may thus state parts (1) and (2) of the input hypothesis as follows:
(1) The input hypothesis relates to acquisition, not learning.
(2) We acquire by understanding language that contains structure beyond our current
level of competence (i + 1). This is done with the help of context or extra-linguistic
information.
A third part of the input hypothesis says that input must contain i + 1 to be useful for
language acquisition, but it need not contain only i + 1. It says that if the acquirer
understands the input, and there is enough of it, i + 1 will automatically be provided. In
other words, if communication is successful, i + 1 is provided. As we will discuss later,
this implies that the best input should not even attempt to deliberately aim at i + 1. We
are all familiar with syllabi that try to deliberately cover i + 1. There is a "structure of the
day", and usually both teacher and student feel that the aim of the lesson is to teach or
practice a specific grammatical item or structure. Once this structure is "mastered", the
syllabus proceeds to the next one. This part of the input hypothesis implies that such a
deliberate attempt to provide i + 1 is not necessary. As we shall see later, there are
reasons to suspect that it may even be harmful.
Thus, part (3) of the input hypothesis is:
