Psychological Constraints on the Teachability of Languages

This paper reports on the influence of formal instruction on L2 acquisition in an instructional experiment with child learners. The main tendency of the findings is that a structure can only be learned under instruction if the learner's interlanguage has already reached a stage one step prior to the acquisition of the structure to be taught. My hypothesis for an explanation suggests that the teachability of L2 structures is constrained by the same processing restrictions that determine the developmental sequences of natural L2 acquisition: since the processing procedures of each stage build upon the procedures of the preceding stage there is no way to leave out a stage of the developmental sequence by the means of formal teaching. Following such a processing capacity approach I reject the assumption that the constraints on teachability can be explained on the basis of linguistic input.