An Automatic Caption Filtering and Partial Hiding Approach to Improving the English Listening Comprehension of EFL Students

Introduction Learning English as a foreign language has been heavily emphasized in Asia owing to its predominance in international communications. Among listening, speaking, reading and writing, listening has been recognized as the most essential aspect of language development (Chung, 1999; Liu, Chen, & Chang, 2009). Due to increasing needs, it has become an important and challenging issue to develop innovative and effective approaches to improving EFL students' English competence. In recent years, the advancement and popularity of computer, communication and multimedia technologies has provided an effective way to facilitate English listening comprehension training (Vanderplank, 2010). Various web-based or computer-assisted learning systems have been developed for conducting English listening activities (Chapelle, 2009; Liu & Chen, 2007; Liu, Liu, & Hwang, 2011). Among various English learning sources, videos are the most popular form for training listening comprehension. Researchers have indicated that simultaneous audial and visual input can benefit foreign language learners (Seo, 2002); therefore, many studies related to EFL learning mainly employ videos as learning materials rather than audios or texts (Chapple & Curtis, 2000; Vanderplank, 2010; Williams & Thorne, 2000). Chapple and Curtis's (2000) have further reported that videos not only help learners improve their listening comprehensions, but also promote their confidence in speaking English, in particular, for those who are not native English speakers, such as EFL students. Furthermore, to assist EFL students in comprehending the learning content, most English learning systems provide subtitles or captions on videos. Subtitles are the on-screen text in the students' native language combined with a second language soundtrack in the video, while captions are the on-screen text in the same language as the soundtrack (Markham, Peter, & McCarthy, 2001; Pujola, 2002). In this study, the term subtitles refers to on-screen Chinese text combined with an English soundtrack, while captions refers to on-screen English text combined with an English soundtrack. There are many advantages of providing captions when using videos as foreign language listening training materials (Yang, Huang, Tsai, Chung, & Wu, 2009). For example, Garza (1991) indicated that the use of captions could bridge the gap between the students' competence in reading and listening; Chung's (1996) study reported that videos with captions helped students associate the spoken and written forms of words more easily and quickly than videos without captions. In the meantime, many studies have shown that subtitles can enhance the reading, vocabulary, and listening competences of the students who learn with videos (Danan 1992; Markham et al., 2001; Hayati & Mohmedi, 2011; Danan, 2010). On the other hand, researchers have reported that relying heavily on subtitles when watching audio-visual materials is not conducive to improving listening proficiency (Latifi, Mobalegh, & Mohammadi, 2011). Some researchers have further indicated that videos without subtitles or captions are more beneficial as they induce students to pay attention to various pronunciation features, such as reduced forms, assimilation, elision, and re-syllabification (Hulstijn, 2003; Field, 2003; Vandergrift, 2007). In sum, although captions and subtitles could be helpful to learners in comprehending learning materials, it is important to provide learning supports that meet individuals' knowledge level at the right time to avoid possible negative effects. Miller (1956) has noted that people's capacity for processing information is limited, implying the need of providing caption-filtering mechanisms in developing learning system for English listening comprehension by taking into account what the learners need based on their knowledge levels. On the other hand, Mayer and Moreno (2003) have indicated the importance of presenting relevant learning materials (e. …