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　　2.2.2 Factors Affecting Listening Comprehension

　　Since listening is a complex active process in which learners decode and construct the meaning of a text by drawing on their previous knowledge about the world as well as their linguistic knowledge, there seem to be many factors that affect listening comprehension. Two factors related to the present study, i. e., repetition and schema, are reviewed in this section.

　　2.2.2.1 Repetition

　　One purpose of this study is to investigate the effects of different listening times (one-time vs. three-time listening) on learners' listening comprehension and incidental vocabulary acquisition. Repetition is an important variable that can affect learners' ability to process the information in a listening task, for it provides more processing time and clarifies the relationship between the syntactic forms. In general, research conducted to date on the effect of repeated exposure has shown that repetition is also an important factor facilitating L2 listening comprehension.

　　Lund (1991) examined the effects of repetition and different course levels (proficiency levels) on the listening and reading comprehension in German as a foreign language of 60 university students in their first, second, and third semesters. He found listening comprehension performance, as measured by propositions and lexical items recalled, improved after a second opportunity to listen to the passage. Results also indicated that this improvement was greater for third-semester learners than it was for learners in the first and second semesters. To be more specific, the improvement of the students' listening recall task in the first and second semesters was about half that of the third-semester students, whereas there was no difference in the improvement among the students at different proficiency levels in the reading recall task. Therefore, he argued that the third-semester students benefited from the repeated exposure in the listening task. The improvement in the listening performance was accounted for by what Lund called “recursive use of the texts”, which provides the learners with “a test structure of meaning to be fit to the text on the next repetition”.

　　To examine the effect of input modification (including repetition) on listening comprehension of Japanese university students, Cervantes and Gainer (1992) conducted two experiments involving about 80 English majors at a university in Japan that compared the effects of listening to simplified input once versus listening to a difficult text with or without repetition. Results of the study showed that both simplification and repetition facilitated more comprehension than unmodified texts. The first experiment showed, unsurprisingly, that the simplified version was easier to understand than the complex one. In the second experiment, no significant difference was found between the group hearing the syntactically simplified version and the group hearing the complex version with repetition. Thus, Cervantes and Gainer argued that although syntactically simplified listening texts may aid comprehension, it may not be necessary if other modification, such as repetition, is available.

　　Berne (1995) investigated the effect of multiple exposures to a video clip on comprehension performance of 62 native English speakers learning Spanish in an American university. Before viewing the video twice, the participants were randomly put into three groups with different pre-listening activities: a question preview activity, a vocabulary preview activity, and a filler activity. Results revealed that scores for all three groups improved significantly as a result of viewing the passage a second time. The researcher thus concluded that “the most effective means of improving listening comprehension performance is through additional exposure to the passage” (p.326).

　　Chang (1999) looked at learners' levels of comprehension as the number of repetitions increased, and her results showed that the number of repetitions required for adequate comprehension depended on the listeners'proficiency level and the difficulty of the listening text. For high-proficiency level listeners, a single repetition was sufficient if the listening text was easy, but for low-proficiency level listeners, the improvement in their listening comprehension was less noticeable even after several repetitions, particularly if the text was difficult or the listeners were unfamiliar with the content.

　　Chang and Read (2006) examined the effects of four different types of listening support (preview of the questions, repetition of the input, provision of topic knowledge, and vocabulary instruction) on the listening performance of 160 Chinese learners of English at a college in Taiwan. They also investigated their interactional effects between types of listening support and listening performance with proficiency levels based on the results of the listening section of the Test of English for International Communication (TOEIC). Results showed that the effects of the four listening support types differed according to proficiency level. The high listening proficiency group outperformed the low listening proficiency group in the condition of repetition of the input, and for the high listening proficiency group, repetition of the input was more effective than any other instructional treatment. Based on these results, Chang and Read suggested that the high listening proficiency group would benefit more than the low listening proficiency group from repetition of the input.

　　Elkhafaifi (2005) studied the impact of pre-listening activities (vocabulary preview or questions preview) and repeated listening exposure on listening comprehension scores of 111 intermediate AFL (Arabic as a foreign language) learners. The students watched a videotaped lecture twice and were tested on their comprehension each time when they finished watching the video. Results showed that although vocabulary knowledge played a significant role in listening performance and providing comprehension questions prior to the listening also helped the students achieve significantly better listening scores, “multiple exposures to the listening passage served as the best predictor of listening proficiency” (p.510). This led the author to conclude that “the single most important factor in improving listening comprehension is repeated exposure to the listening passage” (p.510).

　　O'Bryan and Hegelheimer (2009) used a mixed-method approach to investigate the use and awareness of four intermediate ESL students' listening strategies over the course of one semester at a large midwestern research university in the United States. They also investigated the impact of repetition on listening strategies and on the development of students' metacognitive awareness. Four students, two undergraduates and two graduates, received an informal warm-up with casual conversation before listening to two passages, and a brief reminder of what they were supposed to do while listening. This was followed by a verbal report stage when they listened to the passages for the second time and voiced their thoughts. The researchers found a difference in the strategies used and level of comprehension attained by the participants in the second listening, and thus claimed that the second listening allowed learners “to build up to more complex bottom-up processing strategies, namely using lexical and grammatical relationships to comprehend the input and utilize the information gained from the text to make meaning. ”They argued that “having the opportunity to repeat the text is what facilitated the creation of a framework that resulted in a more coherent summary the second time” (p.26).

　　Sakai (2009) examined the effects of repeated exposure in L2 listening tests of 36 university learners of English in Japan. The participants were divided into two listening proficiency groups and were required to write what they understood after listening to a set of passages twice. All the recall protocols were scored by the researcher, who reported high reliability. Results showed that for both groups of learners, the second effort was better than the first effort, and the study did not find any interactional effect between repetition and proficiency levels. The researcher thus concluded that the effects of repetition, regardless of proficiency level, facilitated listening comprehension of the passage to a similar degree. In an attempt to answer a more interesting research question about the effect of repetition on idiosyncratic recall protocols (i. e., additive information that does not appear in the original text) and misinterpretations (i. e., incorrect recall protocols), results indicated that repetition helped both groups of learners understand the text further and led to more precise comprehension of the passage.

　　Regarding the interactional effect between repetition and proficiency level, it can be clearly seen from the research reviewed above that the results of these studies are mixed. Whereas some (e. g., Chang & Read, 2006; Lund, 1991) reported an interactional effect between repetition and proficiency, other studies (e. g., Cervantes & Gainer, 1992; Sakai, 2009) did not. In an attempt to interpret the mixed results that these studies have produced, Sakai (2009) examined the results of Chang and Read's study and noted that repetition may in fact have improved the performance of both proficiency groups (high and low proficiency groups), but the changes for the low proficiency groups were not sufficient to achieve statistical significance. As for Lund's study, Sakai'noted that Lund found a statistically significant interactional effect only in one of the two analyses of the recall protocol. In addition, Sakai believed “the mixed results of the previous studies may be due to different analysis methods” (p.369). Also, the mixed results of these studies can be accounted for by the fact that they used different tasks to assess listening comprehension (e. g., a free written task [Lund], a multiple-choice test [Chang & Read], a partial dictation task [Cervantes & Gainer], and a free written recall task [Sakai]), which only required test takers to listen to part of the passages.

　　One research purpose of the present study is to investigate the effects of different listening conditions, i. e., of single exposure to a listening passage (listening one time) versus repeated exposure to a listening passage (listening three times), on learners' listening comprehension and incidental vocabulary acquisition. A question of considerable interest is the extent to which repetition assists both vocabulary acquisition and listening comprehension. While there is clear evidence to suggest that repetition aids listening comprehension, little is currently known about whether and how repetition aids vocabulary acquisition.

　　2.2.2.2 Schema

　　Listening is a complex, active process of interpretation in which listeners match what they hear with what they already know (Vandergrift, 2002). Background knowledge plays a crucial role in understanding a language. It is often the absence or incompleteness of background information that results in non-comprehension or incorrect comprehension that L2 listeners experience. In other words, “where the language element in fact presents no obstacle … it is the lack of shared contextual information or schema that makes comprehension difficult or impossible” (Anderson & Lynch, 1988, p.154).

　　First used in cognitive psychology, the word “schema”has been adopted in a number of fields. In the context of listening, “schema”refers to “a mental structure consisting of relevant individual knowledge, memory, and experience, which allows us to incorporate what we hear into what we know” (Anderson & Lynch, 1988, p.139). People have thousands of schemas in their memory and these schemas are interrelated with one another. Every time we are engaged in reading, listening to, or observing something new, by relating one fact to another through logical links, we create new schemas and our existing schemas are updated.

　　Research into the effects of schematic knowledge on L2 comprehension has predominantly focused on reading, rather than listening. Carrell and Eisterhold (1983) explain that background knowledge in the readers' mind can facilitate L2 reading comprehension. Similarly, listening is an interactive process and successful listening comprehension requires an in teraction between the listening context and the listener's existing background knowledge which provides them with a frame of reference where they can combine the new incoming input with the knowledge they already have.

　　Compared with L2 readers, L2 listeners face additional difficulties in making sense of what they hear, especially at lower levels of proficiency, because in most cases speech is temporary, less clearly produced and more implicit than written language. For this reason, the role of schematic knowledge has been recognized as an important factor that affects listening comprehension. Brown and Yule (1983, p.248) describe schema as “organized background knowledge which leads us to expect or predict aspects in our interpretation of discourse”. They explain that listeners'background knowledge and prior experiences predispose them to construct expectations about seven areas: speaker, listener, place, time, genre, topic, and co-text in order to interpret the discourse. Long (1989) further explains that learners construct meaning during the comprehension process through segmenting and chunking the aural input into meaningful units and then actively matching the results with their existing linguistic and world knowledge, a process that enables listeners to make inferences, which is a cognitive strategy used by listeners to facilitate comprehension. Rost (1990, p.70) defines the base or schematic meaning of a text as “the cultural and experiential frame of reference that makes a text interpretable by a listener”.

　　To address the role of schematic knowledge in facilitating L2 listening, Long (1990) explored the effect of background knowledge on L2 listening comprehension. Students of Spanish listened to two passages, one familiar and the other unfamiliar. Comprehension was assessed by a recall protocol in English and a recognition measure. Although no significant differences were found between the familiar and unfamiliar passages, Long attributes this result to the content of the checklist, which was less difficult compared to the recall measure and thus could have enhanced the probability of correct answers. Similarly, in an attempt to examine the effect of topic familiarity on L2 listening comprehension, Schmidt-Rinehart (1994) carried out a study of university students of Spanish who listened to two passages, one about a familiar topic and the other about a novel topic. The results, obtained through a native language immediate recall procedure, showed that the learners scored considerably higher on the familiar topic than on the new one. The study reveals that schematic knowledge in the form of topic familiarity is a powerful factor in facilitating listening comprehension.

　　Tyler (2001) compared the responses of L1 and L2 listeners to spoken texts with or without advanced knowledge of topic. He found that prior knowledge of the topic did not result in any significant difference between the two groups in the demands placed on working memory. Nevertheless, when given no prior information about the topic, the demands placed on working memory were significantly higher for the L2 group than for the L1 group. Tyler thus concluded that background knowledge assists comprehension by freeing up the listeners' mental resources, allowing more attention to be directed at processing the language input.

　　A study carried out by Sadighi and Zare (2006) examined the effect of background knowledge on some upper-intermediate-to-advanced-level Iranian EFL learners' listening comprehension in preparing for their TOEFL exam. The experimental group worked on the topics by using different resources such as the internet before coming to the class. The comprehension test results revealed a significant difference in favor of the experimental group, which lends further support to the importance of schematic knowledge in listening comprehension.

　　Besides the studies investigating the role of general background knowledge by exploring the influence of learners'content schemata, some studies (e. g., Hohzawa, 1998; Chang & Read, 2006) also included pre-listening activities or advance organizers to prepare students by activating their background knowledge about unfamiliar topics. In virtually every listening situation, it is clearly advantageous to comprehension for listeners to call on knowledge from their stored prototypes. Once the knowledge is activated, additional information, stored as related schemata, becomes available to the listener. Meanwhile, whenever a knowledge structure is activated, the listener also experiences an affective response which further influences connections with the speaker's own ideas, and elicits an empathic response.

　　Activation of prior knowledge has been shown to have salutary effects on L2 listening success (e. g., Long, 1990; Schmidt-Rinehart, 1994). Research into pre-listening activities has documented positive effects on listening performance for advance organizers (Chung, 2002; Herron, Cole, York, & Linden, 1998), question type (Flowerdew & Miller, 2005), and question preview (Elkhafaifi, 2005). These studies have demonstrated that it is helpful to provide learners with a context before they begin to listen.

　　Mendelsohn (1995, p.140) identifies the importance of pre-listening activities in facilitating L2 listening comprehension as they “activate the students'existing knowledge of the topic in order for them to link what they comprehend and to use this as a basis of their hypothesis-information, prediction, andinferencing”. Providing listeners with the knowledge or contextual support required for the task can orient them to what they are about to listen to, thus directing their attention to the task rather than having them listen aimlessly.

　　Hohzawa (1998) found that providing listeners with a chance to activate their prior knowledge affected comprehension and the kind of processing L2 listeners did. He tested the comprehension of 58 low intermediate Japanese students in an intensive English program, where the students were assigned to “background information”and “no background information”groups. Students took a proficiency test and were tested on their familiarity with the topics of three news stories. Then they listened to the stories, wrote recalls, took a comprehension test, and re-took the familiarity measure. In addition, the students in the “background information”group heard the introduction to the news stories and discussed the content of the stories briefly. Hohzawa found that students who established background information tended to use more top-down processes and that their comprehension was greater than the students in the “no background information”group.

　　Chang and Read (2006) investigated the effectiveness of providing four types of listening support to EFL learners: topic preparation, vocabulary instruction, question preview, and repeated input. The results of the study showed that the most effective type of support was providing prior information about the topic. In addition, the fact that mean scores of the high and low level language learners in the topic-preparation group were quite similar showed that providing background knowledge about the topic enabled the low level learners to compensate for their limited language knowledge.

　　Al Alili (2009) designed a study to determine whether learners' listening comprehension of an unfamiliar text would vary as a function of different advanced organizers to activate the background knowledge. Three groups of Arabic-speaking EFL learners were involved in the study. In one experimental group the content schema (knowledge about the topic) was activated, and the formal schema (knowledge about text structure and discourse organization) of another experimental group was activated, and the control group received neither type of advanced organizer. The results of a listening comprehension test indicated that learners whose content background knowledge was activated scored slightly higher than those whose formal background knowledge was activated. Statistical analysis, however, showed no significant differences. Nevertheless, based on responses to a post-study questionnaire, the students in the experimental groups perceived the pre-listening activities to be very helpful in enhancing their understanding and prediction of the listening text. The results of this study support the importance of helping learners make connections between their existing knowledge and the incoming aural input.

　　Because of the demands of listening, L2 listeners are likely to be forced to rely on their background knowledge to interpret the text more than L2 readers are (Lund, 1991). It may be that prior knowledge actually primes linguistic forms and their meanings and allows listeners to take a broader view of a text and make predictions (Conrad, 1989). In other words, it may be that prior knowledge allows listeners to devote less working memory to processing the input linguistically, and so to comprehend more with less effort (Tyler, 2001).

　　To sum up, the results of the research reviewed above were not unanimous concerning the role of schematic knowledge in facilitating L2 listening. On the one hand, Schmidt-Rinehart (1994) and Sadighi & Zare (2006) found significant L2 listening differences in favor of the experimental group with schematic knowledge, and they thus lent further support to the importance of schematic knowledge in listening comprehension. On the other hand, Long (1990) and Tyler (2001) could not find significant differences between the groups with and without prior information ontopic, though Tyler commented that background knowledge assisted comprehension by freeing up the listeners' mental resources, allowing more attention to processing the language input. Regarding the role of pre-listening activity in facilitating L2 listening comprehension, schema-raising activity was proved to be an effective type of listening support in enhancing learners'understanding and prediction, for it both helped the higher level learners to use more top-down processes and enabled the low level learners to compensate for their limited language knowledge. However, these studies made no attempt to investigate the effects of schema raising as a type of pre-listening training on learners' incidental vocabulary acquisition from listening activities and none of the studies was administered in a Chinese context.

　　One of the research purposes concerning this study is to investigate the effects that a schema raising activity prior to listening has on learners' listening comprehension and incidental vocabulary acquisition. A question of considerable interest is the extent to which a schema raising activity assists both vocabulary acquisition and listening comprehension. While there is clear evidence to suggest that it aids listening comprehension, little is known to date about whether and how a schema raising activity prior to listening aids vocabulary learning through listening. 元认知策略研究：二语听力理解与附带词汇习得（英文版）