This study examined the effects of exposure frequency in restructuring and strengthening the representation of multiword sequences in the L2 mental lexicon. In a classroom setting, a text-shadowing task was assigned to undergraduate students. Through the sound-utilizing shadowing training, the amount of exposure to the target items was carefully controlled, six times (SH6) for the treatment group and three times (SH3) for the control group. The results showed that in a pre-, post-, and delayed-post design, all the participants increased their productive and receptive knowledge of the target phrases after the training. However, the impact of exposure frequency was much larger for the acquisition of productive knowledge, with constantly higher percentage gains in SH6 both immediately after the training and after a four-week interval. In contrast, no statistical difference was found between the groups in receptive knowledge. The significantly lower retention rates of productive knowledge suggests that the importance of exposure frequency is critical in establishing a more entrenched representation of multiword expressions promoting formulaicity, or single unit status, for more productive use of language.
