research (Leeman, 2003) reported that implicit corrective feedback was more influential than explicit feedback. However, in this case the explicit feedback took the form of ‘source of problem indicated’ as Leeman’s research, which was primarily related to investigating the relative influences of significant evidence and just negative evidence on acquisition (Alison Mackey, 2007). Meanwhile, Mackey (2007) reported that it is difficult to come to an exact conclusion considering the relative effectiveness of implicit and explicit corrective feedback according to researches for a number of reasons. First, the two types of feedback were not operationalized in the same way in all the researches. Implicit feedback was implemented as recasts in most of the investigations, but recasts can differ enormously. The explicit feedback also differed if it simply showed an error had been occurred, presented a correction, or involved metalinguistic information or some combination of these strategies. In addition , according to Han’s (2002b) comment, the recasts are emphasized intensively on a single grammatical structure (Alison Mackey, 2007). As Doughty (2003) remarks, a second reason why the results of previous investigations are difficult to interpret is the method of implementing and testing acquisition. Most of the researches did not include measures of implicit knowledge i.e. a general failing in form- focused instruction studies. And to complete this, the researchers found explicit corrective feedback to be the more influential (Mackey, 2007). Finally, the previous researches differed in their selection of aimed grammatical structure. Some of the researchers investigated morphological features- for example, distinguishing nouns and verbs in Carroll (2001) and or French grammatical gender in Lyster (2004) – while other res>