The effectiveness of intensive and extensive recasts on L2 acquisition for implicit and explicit knowledge

• Recast groups produced better test scores than the control group.
• Recasts were effective even for a structure that learners were unfamiliar with.
• The effectiveness of recasts was sustained for a week.
• Intensive recasts were more effective than extensive recasts for implicit knowledge.
• Intensive and extensive recasts were equally effective for explicit knowledge.

This study was conducted to compare the effectiveness of intensive and extensive recasts on the acquisition of a planned target structure. The study consisted of a control group and two treatment groups, one of which received intensive recasts on errors only for English unreal conditionals; the other received extensive recasts on any kind of error during 2-h activity sessions. A total of 44 ESL learners participated in the experiment. Results showed that (a) the groups receiving recasts demonstrated higher accuracy on tests of both implicit and explicit knowledge when compared to the control group; (b) the intensive recast group showed a trend toward greater accuracy than the extensive recast group on the implicit knowledge tests; (c) both intensive and extensive recast groups demonstrated similar accuracy on the explicit knowledge test, and (d) the effectiveness of recasts was evident even for a structure that the learners were still unfamiliar with.