The experiment was conducted for a month, as shown in Figure 1. The participants used PDAs (Personal Digital
Assistants) to play the instructional video related to the lesson they studied in class each week. After spending time
watching the video, they immediately took a test to evaluate their listening comprehension proficiency and
vocabulary acquisition. Although this study provided PDAs as dedicated devices, it should be noted that other mobile
devices, such as smartphones or e-books, could also be used to conduct the same learning activity.
During the learning activity, a video without any English captions or Chinese subtitles was used for the students in
the control group because previous studies have indicated that providing no captions or subtitles helps students adapt
to various pronunciation features, such as reduced forms, assimilation, elision, and re-syllabification (Vandergrift,
2007).
On the other hand, a video with full English captions and Chinese subtitles of only the target vocabulary was used for
the students in experimental group one because a previous study showed that such a setting is helpful in training
listening proficiency and comprehension, and confirmed that full Chinese subtitles are not needed (Hsu & Chang,
2010). Another video with both English captions of the target vocabulary and Chinese subtitles of the target
vocabulary was used for the students in experimental group two.