What characteristics of recasts facilitate accurate perception when overheard by true beginners?

In this study, 118 native speakers of Japanese watched 48 separate video clips in which a teacher provided recasts on phonological or lexical errors to students in Portuguese, a language with which the participants were unfamiliar. In the video clips, six recast characteristics were manipulated: length, segmentation (segmented/whole), prosodic emphasis (stressed/non-stressed), intonation (declarative/interrogative), head movements (nodding/shaking), and gestures (beat/deictic/metaphoric). Participants judged whether or not the teacher had corrected errors and stated the reasons for their decisions. Multiple regressions extracted segmentation and gestures as being significant variables for both phonological and lexical errors. Precisely speaking, recasts were more likely to be accurately perceived as correction when they were provided in sentence-length discourse along with deictic gestures. Additionally, head-shaking and beat also contributed to improved accuracy of phonological errors. The analysis of their reasoning indicates that the participants actively compared errors with recasts when judging the presence of a recast. The overall results indicate that contrary to the common belief suggesting that shorter recasts are better than longer ones, when true beginners overhear recasts, they may find it easier to notice the corrections when they are provided in sentence-length discourse; as such recasts facilitate more accurate perceptions.