Implicit and explicit instruction: what type of knowledge is promoted? : An empirical study investigating the effects of processing instruction, metalinguistic rule instruction and textual enhancement

Research has shown that input is essential to second language (L2) learning, but input alone may not always be enough for learning to occur. Specifically, adult learners need a pedagogical intervention such as form-focused instruction in order to gain proficiency in the L2. Form-focused instruction varies in its levels of explicitness as it comprises implicit types of training such as input enhancement and more explicit interventions like processing instruction. The effectiveness of implicit and explicit form-focused instruction has not been conclusive. Namely, there is contradicting evidence about whether both implicit and explicit form-focused instruction promote implicit or explicit knowledge respectively or whether each promotes both types of knowledge. There is also no certainty about the types of target forms that are more likely to be learned through implicit or explicit instruction. The present study addresses these shortcomings by reporting the main findings of a lab experiment conducted over a six-week period with university students learning English in Mexico. A pool of 124 learners of English as a foreign language participated. The linguistic target chosen for this study was the use of three prepositions: in, on and by which co-occur in the context of forms of transportation. Measures of implicit and explicit knowledge were used before and after giving all participants three training sessions to assess their progress. A delayed posttest was used to measure if any of the treatments had any long-term effects. Participants were randomly assigned to four different training conditions which varied in their degrees of explicitness. All participants except for those assigned to the control condition received exposure to textual enhancement. The textual enhancement condition did not involve any explicit type of instruction. The metalinguistic instruction condition comprised an explanation of three target rules in addition to textual enhancement. The processing i