Questions asked Ricardo during the first few months of his stay in the United States included:

    What do we mean by question mark?
    Did you ever have any trouble with your ears?

Wagner-Gough and Hatch suggest that it was this input difference, rather than the age difference between Paul and Ricardo, that was the fundamental reason for their differential success in acquiring English as a second language.

What could we have done for Ricardo? I can think of at least three ways Ricardo could have been provided with simpler input in English. First, he could have been a member of a "pull-out" class in school, either in English as a second language or in one or more subject-matters. This segregation from native speakers of English, distasteful to some, would have at least encouraged a simpler "teacher-talk" from his instructors, as all students in the class would have been less than fully competent speakers of English. Second, we could have provided Ricardo with opportunities to meet native speakers of English (for one method, see Krashen, 1978e). These speakers may have provided him with "foreigner-talk". A third possibility would have been to set up some mechanism for Ricardo to come into contact with other ESL acquirers, through an ESL or pull-out class or through some other means. As long as such a foreign student peer group had different first languages, this would have provided Ricardo with "interlanguage" input, another simpler code.

But would any of these simple codes have helped Ricardo acquire English? This is, I believe, a question of immense theoretical and applied interest, as fundamental as any in our field. On the theoretical level, it asks how acquirers acquire, or what "intake" is. On the applied level, it asks what sorts of environments are best for second (or first) language acquisition, a continuation of the discussion of formal and informal environments, previously dealt with by Krashen and Seliger (1975), d'Anglejan (1978), Tucker (1977), Stern (1978), Palmer (1978), and Chapter 3 of this volume.

Before discussing possible approaches to answering this question, some brief definitions are in order. We will focus on three sorts of simple codes that second language acquirers are apt to come into

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