Some researchers suggest that recasts are effective in showing learners how
their current interlanguage differs from the target (Long & Robinson, 1998
). Others have argued that recasts are ambiguous and may be perceived by th
e learner as confirmation of meaning rather than feedback on form (Lyster,
1998a). We review research on the effectiveness of recasts in first and sec
ond language acquisition, paying particular attention to how recasts have b
een defined and how their impact has been assessed in observational and exp
erimental studies. We conclude that recasts appear to be most effective in
contexts where it is clear to the learner that the recast is a reaction to
the accuracy of the form, not the content, of the original utterance.