However, linguistic input is extremely abundant, dense and complex. Babies hear many thousands of hours of connected speech, from which they must isolate forms and map meanings to understand and then produce their own utterances. Second language learners face a similar task, through the filter of their L1 competence.
How do learners begin to process linguistic information?
Pitt Corder was the first to distinguish input from intake.
The simple fact of presenting a certain linguistic form to a learner in the classroom does not necessarily qualify it for the status of input, for the reason that input is 'what goes in' not what is available for going in, and we may reasonably suppose that it is the learner who controls this input, or more properly his intake. This may well be determined by the characteristics of his language acquisition mechanism and not be those of the syllabus. After all, in the mother-tongue learning situation the data available as input is relatively vast, but it is the child who selects what shall be the input.
(Corder, 1967, p. 165)