Prior to the development of the idea of interlanguage,
contrastive analysts had asserted that the
second-language learner’s language was shaped solely
by transfer from the native language. Because this
was assumed to be so, a good contrastive analysis of
the NL and the TL could accurately predict all the
difficulties that learner would encounter in trying to
learn the TL. These claims were made on logical
grounds and almost always supported only by reference
to anecdotal evidence. It is important to note
that these claims were not supported by reference to
data obtained from the systematic study of learner
language itself, but usually only to utterances that
analysts happened to have noticed and remembered.
Unfortunately, it is all too likely that analysts tend to
notice data that their theories predict and not to
notice data that do not fit their theories. Learner
utterances that were clear evidence of transfer were
noticed and quoted, but learner utterances that did
not provide evidence of transfer apparently went
unnoticed or were classified as ‘residue.’ Thus, in the
late 1950s and the 1960s, there were virtually no
systematic attempts to observe learner language and
to document scientifically the way in which learner
language developed, or to independently and objectively
verify the strong claims of the contrastive analysis
hypothesis that language transfer was the sole
process shaping learner language.