Language Learning 51:2, June 2001, pp. 257–280 Resource Consumption as a Function of Topic Knowledge in Nonnative and Native Comprehension Michael D. Tyler University of Western Sydney Previous research suggests that low-level receptive language processes are less developed for nonnative than for native listeners, yet experienced nonnatives seem to comprehend effortlessly in everyday situations. One possible explanation is that experienced nonnatives use topic knowledge to reduce working memory (WM) requirements. Native and experienced nonnatives attended to Bransford and Johnson’s (1972) Washing Text while performing a concurrent task, with half of each group given the topic of the passage. Scores on the concurrent task were compared with baseline to index WM consumption. The results showed a relatively greater WM consumption for nonnatives than natives when the topic was unavailable, suggesting that nonnatives rely more than natives on topic knowledge in comprehension. Implications for foreign language learning are discussed. Michael D. Tyler, Macarthur Auditory Research Centre, Sydney. I would like to thank Dr. Kate Stevens and Prof. Denis Burnham, from the Macarthur Auditory Research Centre, Sydney, for their helpful comments on earlier drafts of this paper, and Bruno Di Biase from the University of Western Sydney’s Language Acquisition Research Centre for his assistance in recruiting volunteers for the study. Correspondence concerning this article may be sent to Michael D. Tyler, Macarthur Auditory Research Centre, Sydney, University of Western Sydney, Locked Bag 1797, South Penrith Distribution Centre, South Penrith, New South Wales, 2560, Australia. Internet: [email protected] 257 258 Language Learning Vol. 51, No. 2 There are many people who live in an environment where their native language is not spoken and who conduct their daily business using a nonnative language. There has been a great deal of research examining the nonnative speech of these individuals, but far less on their receptive language capabilities. Most researchers studying second language (L2) acquisition agree that if people start learning a language as an adult, their accent will be clearly distinguishable from that of a native speaker (e.g., Flege, Yeni-Komshian, & Liu, 1999; Scovel, 1988). However, research in the area of L2 speech perception has also led to the idea that nonnatives may not only speak with an accent, but also hear with an accent (Jenkins, Strange, & Polka, 1995). For example, there is a large body of literature demonstrating that native Japanese listeners have poorer discrimination of English /r/ and /l/ than native English listeners (e.g., MacKain, Best, & Strange, 1981; Sheldon & Strange, 1982), even after 12 years of naturalistic exposure to English (Takagi & Mann, 1995). One possible explanation for this finding is that the low-level processes involved in the perception of these phonemic contrasts are less developed for nonnative than for native listeners. The results of several other studies support the notion that nonnative low-level processes are less developed than native processes. For example, using grammaticality judgement tasks, Johnson, Shenkman, Newport, & Medin (1996) showed that nonnative speakers have an indeterminate grammatical system. Emmorey and Corina (1990) administered a gating task to late learners of American Sign Language and to native signers, and they found that native signers were able to guess the identity of the sign significantly earlier than nonnative signers. They argued that this demonstrated differences in processing at the early stages of lexical recognition, perhaps reflecting differences in processing capacity or in the structure of lexical representations. Mayo, Florentine, and Buus (1997) administered the Speech Perception in Noise test to monolingual English speakers and to early and late bilingual Mexican-Spanish speakers. They found that English speech was intelligible at higher levels of noise for Tyler 259 monolinguals and early bilinguals than for late bilinguals, which is also consistent with the idea that nonnative listeners have less developed low-level language processes than native listeners. If it is the case that nonnative low-level processes are less developed than native low-level processes, then one might expect some difficulty in comprehending speech in the nonnative language. The concept of difficulty is accounted for by theories of attention. For example, Navon and Gopher (1979) defined difficulty as “the subjective feeling of strain accompanying involvement in demanding tasks” (p. 215). They stated that when a task is demanding, larger amounts of mental resources are required to perform the task. With practice and experience, performance becomes automatic rather than controlled, the amount of required resources decreases, and the task becomes less demanding (Schneider & Shiffrin, 1977; Shiffrin & Schneider, 1977). A more recent theory that deals specifically with resource consumption in language comprehension is Just and Carpenter’s (1992) theory of working memory (WM). According to this theory, human comprehension ability is constrained by a pool of WM resources that fuels both the computation and storage of information. Difficulty in comprehension occurs when the amount of available WM is too small to cope with the demands of storage and computation. In the case of foreign language listening, at the beginning stages of learning, attention is focused on low-level processes such as phoneme discrimination and word recognition. Large amounts of WM resources are required for these unfamiliar tasks, so performance is difficult. The negative effect of this difficulty on motivation and the associated increase in anxiety is well documented (MacIntyre & Gardner, 1991; MacIntyre & Gardner, 1994; Schumann, 1998). According to theories of attention, with practice and experience, performance in all of these domains should become automatic, and fewer WM resources should be required for L2 listening. Indeed, in everyday conversation, experienced nonnatives living and working in nonnative language environments appear to experience no more difficulty in comprehension than native listeners. However, if low-level receptive language processes are less 260 Language Learning Vol. 51, No. 2 developed for nonnative listeners than for native listeners, then a larger resource allocation would be expected for nonnatives than natives during language comprehension. Therefore, there seems to be a gap between observed performance in the real world and the predicted performance from experimental results. One possible factor contributing to the seemingly effortless comprehension abilities of experienced nonnatives is topic knowledge. That is, the topic of conversation can provide cues to meaning. For example, Bransford and Johnson (1972) showed, with native listeners and written stimuli, that the recall of information from vague passages could be improved by the provision of a relevant picture or topic. For example, in one experiment they presented the following passage: The procedure is actually quite simple. First you arrange things into different groups. Of course, one pile may be sufficient depending on how much there is to do. If you have to go somewhere else due to lack of facilities that is the next step, otherwise you are pretty well set. It is important not to overdo things. That is, it is better to do too few things at once than too many. In the short run this may not seem important but complications can easily arise. A mistake can be expensive as well. At first the whole procedure will seem complicated. Soon, however, it will become just another facet of life. It is difficult to forsee any end to the necessity for this task in the immediate future, but then one never can tell. After the procedure is completed one arranges the materials into different groups again. Then they can be put into their appropriate places. Eventually they will be used once more and the whole cycle will then have to be repeated. However, that is part of life. (p. 722) Participants who were not given the topic of this passage were able to recall less information than those who were given the topic, which was “Washing Clothes.” Similar findings have been reported for students learning a foreign language (see Schmidt-Rinehart, 1994, for a review). Students are able to recall more information from foreign language passages when the topic is familiar than when it is unfamiliar. For Tyler 261 example, Markham and Latham (1987) presented Muslim and Christian students with novel foreign language texts describing religious practices from these faiths. They found that the Muslim students were able to recall more information from the Muslim texts, and the Christian students could recall more information from the Christian texts. Rather than recruiting foreign language students from different backgrounds, Wolff (1987) used Bransford and Johnson’s (1972) Balloon Story to manipulate access to the topic directly. Like the Washing Text, the Balloon Story is vague, but when a contextual picture was provided, the passage was easy to follow. Wolff presented the Balloon Story to foreign language students, with half also given the contextual picture to aid comprehension. The results replicated Bransford and Johnson’s findings, because superior recall was obtained when the picture was provided compared to when there was no picture. Wolff interpreted these results, and the results of similar tasks using other passages, in terms of information processing theory. He argued that the bottom-up processes that nonnative listeners use to decode the speech signal are underdeveloped, so they must resort to top-down processing to achieve comprehension. In other words, when the topic is not known, nonnative listeners need to rely on their underdeveloped low-level processes for comprehension, but if the topic is available, then knowledge about the world can be used to aid comprehension, and less information is required from the speech signal. In terms of working memory, if the topic is known, then nonnatives need to rely less on low-level processes for comprehension, leaving more resources for higher-level comprehension processes. Therefore, it is possible that the seemingly effortless comprehension performance of nonnative listeners in everyday situations is due to knowledge of topic. That is, if nonnatives “hear” with an accent, then topic knowledge may be more beneficial for nonnative comprehension than for native comprehension. The aim of the present study is to ascertain the effect of topic knowledge on the allocation of WM resources in experienced nonnative comprehension 262 Language Learning Vol. 51, No. 2 compared with native comprehension. It is predicted that the difference in the availability of WM resources between when the topic is given and when no topic is given will be greater for nonnatives than for natives. Before describing the task used here for measuring WM availability during comprehension, it is necessary to address some theoretical issues. The first section will justify the selection of nonnative participants for the study and the second section will describe a recent theory of comprehension that is compatible with Just and Carpenter’s (1992) theory of WM. Experience Versus Proficiency in the Selection of Nonnative Listeners In my description of the target nonnative group for the present study, I have used the term “experienced,” rather than “proficient,” the latter being more common in second language acquisition research. In a review of the assessment of nonnative language proficiency, Thomas (1994) identified four main methods: Impressionistic judgement, institutional status, in-house assessment instruments, and standardized test scores. The use of standardized test scores would be the most appropriate of these four for the present study if proficiency were the criterion of selection. However, these tests often suffer from the “comparative fallacy” (Bley-Vroman, 1983), owing to their inherent comparisons with native-speaker norms. That is, it is possible that the outcome of nonnative language acquisition is qualitatively different from native language acquisition, so a bias may be introduced if certain nonnatives are excluded because they fail to perform at nearnative levels on language tests (Bley-Vroman, 1989, 1990). The distinction between native and nonnative is also controversial, because the issue of maturational constraints on language acquisition is still a matter of debate (e.g., Birdsong, 1999; Flege et al., 1999). Within this literature, there appears to be a consensus that the outcome of nonnative language acquisition after the age of 15 is different from early nonnative language acquisition and from Tyler 263 native language acquisition, but there is disagreement about the source of the difference. Both controversies can be avoided by using the criteria of Johnson et al. (1996) to select proficient nonnatives. Their nonnative participants were not exposed to English before the age of 10, arrived in the United States after the age of 15, and had been residing there for at least 5 years. Furthermore, all participants were graduate students who were exposed to English on a daily basis. According to Johnson et al., individuals who conform to these criteria have reached an end-state in their language acquisition, such that their proficiency, relative to native speakers, will no longer improve or deteriorate. The present study recruited nonnative listeners who conformed to these criteria, because both of the controversies would thus be avoided. The nonnative participants of Johnson et al. were all older than 15 when immersed in an English speaking environment and so were outside the influence of maturational constraints, and comparison with native speaker performance was not required, because a criterion of experience rather than proficiency was used. Comprehension as the Formation of a Mental Model Comprehension is not a unitary concept. As Glenberg, Kruley, and Langston (1994) have pointed out, we can talk of comprehending words, phrases, sentences, or discourse. Furthermore, comprehension processes are not necessarily specific to language, because people can also comprehend the physical and social worlds through other sensory observations. The present study is concerned with the comprehension of everyday spoken language, that is, language that occurs at the discourse level. Comprehension gained from other sources therefore needs to be carefully controlled. Recently, researchers have begun to examine comprehension processes in more detail. Comprehension is now seen as tantamount to the formation of a mental structure of a situation described in language, or observed in reality. These mental structures are 264 Language Learning Vol. 51, No. 2 known as situation models, or mental models (see Zwaan & Radvansky, 1998, for a review). Mental models are not the same as Bartlett’s (1932) well known “schema” construct, which has been used previously in L2 acquisition research (e.g., Anderson & Pearson, 1984; Carrell, 1984, 1987). Schemata are representations of canonical or stereotypical situations, whereas mental models are representations of specific situations in space and time. For example, knowledge of the general procedure involved in washing clothes is represented by a schema, but if a person tells a story of their experience doing the washing, then that specific situation is represented by a mental model. So, although schemata are not mental models, they can be used to aid in the construction of a mental model by providing a framework of expectations for a specific situation. If the listener possesses, for example, a schema for washing clothes, then the storyteller needs to provide less information for the listener to construct a coherent mental model. Another property of mental models is that they are constrained by working memory (Glenberg & Langston, 1992; Zwaan & Brown, 1996). If the processes required to form a coherent mental model require more WM resources than are available, then the reader or listener will experience difficulty. Furthermore, Just and Carpenter (1992) state that a reduction in WM demands can be achieved by the preactivation of relevant concepts, relations, and schemas. In other words, the use of topic knowledge to activate an existing mental model reduces WM demands. On the other hand, if the reader or listener is not aware of the topic, then the mental model must be constructed from the beginning, which requires a far greater amount of WM. An On-Line Task to Measure Resource Allocation in Comprehension Bransford and Johnson (1972), using the Washing Text, showed that access to topic can improve recall, so this passage will also be used in the present study to manipulate access to topic. However, the dependent measure in this, and in other studies that have investigated the effect of topic knowledge on comprehension, Tyler 265 has been recall of information. This measure does not necessarily provide information about WM resource allocation during comprehension, so it is inappropriate for the present study. Furthermore, the use of recall as a dependent variable is problematic, because it necessarily follows comprehension and may involve processes of construction or reconstruction (Trabasso & Suh, 1993). Any differences in recall performance could be attributable to problems at the stages of encoding, storage, or retrieval of information. A more appropriate task to measure WM resource allocation during comprehension is one which takes its measurements while comprehension is occurring. In other words, an “on-line” task is required. Takano and Noda (1993) devised an on-line task to measure the decline in the ability to perform a concurrent task during foreign language use. Their participants completed double-digit calculations on a sheet of paper, while answering questions at regular intervals. They found that participants made less correct calculations when answering questions in their nonnative language than in their native language. Takano and Noda (1995) called this the “Foreign Language Effect.” The question-and-answer paradigm used in Takano and Noda’s (1993) study could be altered to accommodate the presentation of the Washing Text. However, one problem is that there is no record of the timecourse of performance on the task, because the responses to the calculations are recorded on a sheet of paper. A more appropriate task would be a computer task requiring only single keystrokes. Another problem is that Takano and Noda (1993) clearly stated that the task does not measure nonnative language processing difficulty per se, but only the decline in thinking ability which accompanies it. For the present study, a task is required that measures comprehension difficulty as directly as possible. This can be achieved by selecting a competing task that requires WM resources, but only minimally involves linguistic processing. One such task is the verification of singledigit calculations (De Rammelaere, Stuyven, & Vandierendonck, 1999; Lemaire, Abdi, & Fayol, 1996), in which participants are presented with a sum (e.g., 2 + 4 = 6) and must indicate whether 266 Language Learning Vol. 51, No. 2 the total is correct or incorrect. This task is also amenable to computer presentation and requires only a single keystroke for responding “correct” or “incorrect.” Therefore, in the present experiment, the participants were instructed to divide their attention equally between verifying the totals of single-digit calculations and trying to remember facts from the Washing Text, which was presented simultaneously through headphones. Half of the participants in the native and nonnative groups were presented with the topic of the Washing Text. If the participants divided their attention equally between the two tasks, then the number of correct calculations achieved in the verification task will provide an indication of WM resource consumption while participants were attending to the Washing Text and remembering information for later recall. Even though the results of the recall task were not used, it was important that the participants be asked to recall the information to ensure that they were attending to the passage. To overcome individual differences on the calculation verification task, the number of correct verifications in the dual-task condition was subtracted from the number of correct verifications in a baseline condition, in which the participants performed a verification task on its own, to obtain a “working memory index score.” In summary, the experiment was a 2 × 2 (Language Background × Topic) between-subjects design with “WM index score” as the dependent variable. It was hypothesized that some nonnative language processes might require effortful processing, so nonnative listeners would use topic knowledge to assist their comprehension more than would native listeners. If this was the case, then an interaction between Language Background (Native/ Nonnative) and Topic (Topic/No Topic) was to be expected, with a greater difference in WM consumption between nonnative and native listeners when no topic is provided than when the topic is provided. Tyler 267 Method Participants There were 30 native Australian English listeners and 30 nonnative listeners in the study. The participants in each group were randomly allocated to the Topic condition (Native: Mean age = 32.1, SD = 14.5; Nonnative: Mean age = 44.2, SD = 11.4) or the No Topic condition (Native: Mean age = 28.1, SD = 12.3; Nonnative: Mean age = 38.9, SD = 10.8), with 15 participants in each group. As the mean ages appear different, a 2-way ANOVA was performed on the age data, which revealed a significant main effect for Language Background (F(1,56) = 12.9, p < .05, ηp2 = .187), but not for Topic (F(1,56) = 2.1), and no interaction (F(1,56) = 0.05). This means that there was no significant age difference between participants in the Topic and No Topic conditions, but there was a significant overall age difference between the native and nonnative listeners. This significant main effect for age should not affect the results of the experiment, because an interaction was predicted for the difficulty index scores between Language Background and Topic, and there is no significant interaction for age. The volunteers were obtained from classes at the University of Western Sydney, Australia, and from the general public by word-of-mouth. All participants reported having normal hearing. The nonnative listeners were all university students or professional people who used English on a daily basis, and they also conformed to the nonnative speaker criteria of Johnson et al. (1996). There were no significant differences between the nonnative Topic and No Topic groups in mean age of arrival in Australia (t(28) = –.47, p > .05; Topic: M = 24.6, SD = 8.0; No Topic: M = 25.9, SD = 6.8), or for the mean age at which the participants began learning English (t(28) = .38, p > .05; Topic: M = 17.8, SD = 6.3; No Topic: M = 16.9, SD = 6.1). However, there was a significant difference between the groups on mean length of stay in Australia (t(28) = 2.1, p < .05, d = .77; Topic: M = 19.5, SD = 9.9; No Topic: M = 12.8, SD = 7.1). The nonnative participants came from a 268 Language Learning Vol. 51, No. 2 variety of language backgrounds, as shown in Table 1. The random allocation of participants into the Topic or No Topic condition resulted in a slightly larger number of participants from Asian language backgrounds in the No Topic condition (n = 7 of 15) than the Topic condition (n = 3 of 15). Materials and Apparatus Bransford and Johnson’s (1972) Washing Text was recorded by a native Australian English male speaker at a rate of 153.5 words per minute, for a duration of 68 seconds, and then digitized at a sampling rate of 11.025 kHz. A practice passage was also recorded, but digitized at a sampling rate of 7.35 kHz to lower computer memory requirements. The practice passage consisted Table 1 Distribution of nonnative language backgrounds in the Topic and No Topic conditions Condition Language Cantonese Czech Danish French German Hungarian Indonesian Japanese Khmer Lebanese Romanian Serbian Spanish Vietnamese Topic No Topic 1 1 1 2 1 1 1 3 1 1 1 1 1 4 2 1 4 3 Tyler 269 of a series of sentences describing a country, but the name of the country was not given, making it similar to the No Topic condition. The calculation stimuli for the verification task were adapted from Geary, Cormier, Goggin, Estrada, and Lunn’s (1993) study. They imposed the following constraints on the stimuli to ensure that the items were of equal difficulty: (a) The augends and addends must be single digits, ranging in value from 2 to 9 (for example, 10 + 1 = 11 is unacceptable, because both the augend [10] and the addend [1] are outside this range); (b) No calculation may contain an augend and an addend of the same value (for example, 3 + 3 = 6 is not an acceptable calculation); (c) Incorrect totals must not deviate from the correct total by more than 2; (d) The pool of calculations must not contain more than four consecutive calculations requiring the same response. The application of these constraints resulted in a pool of 56 correct calculations. Another list of 56 calculations was constructed, where one quarter of the calculations were each randomly allocated an incorrect total with a deviation of –2, –1, +1, or +2. Three further lists were constructed, such that the distribution of incorrect deviations was orthogonal. This resulted in 4 lists of 112 items, which is a greater number of items than participants could complete in 68 seconds. Two of these lists were used in the experiment, and another was reduced to 20 correct calculations and 20 incorrect calculations for the practice session. The experiment was run with SuperLab software (Haxby, Parasuraman, Lalonde, & Abboud, 1993) on a range of Macintosh computers, ranging from LC to Power Macintosh 7300. To overcome any nonrandom variation due to screen refresh rates between computers, the presentation of each calculation was preceded by a 200ms delay minus the presentation time. The passages were presented through headphones, and the participants responded to the verifications by using the index fingers of both hands, one for correct and the other for incorrect. A green tick (check mark) was present on one side of the screen throughout the experiment to indicate which hand to use for a correct response and a red cross was present on the opposite side of the screen. The 270 Language Learning Vol. 51, No. 2 location of the tick (left or right) was counterbalanced across participants. Procedure There were four sections in the experiment: a practice session for the calculation verification task, the single-task condition, the practice passage, and the dual-task condition. First, the participants were given a practice session of 36 calculation verifications to familiarize them with the task. Second, in the single-task condition, participants had 68 seconds to complete the calculation verifications as quickly and as accurately as possible. Third, the same practice passage was presented to all participants, who were told that the passage described a country. They were instructed to try to remember as many ideas as possible from the passage to write down at its conclusion. As recall was not the dependent variable, the modality of responding was unimportant. The participants were aware that the passage was for practice only, so the results were not analyzed. In the final section, the participants were instructed to divide their attention equally between verifying the calculations as quickly and as accurately as possible, and trying to remember information from the Washing Text for later recall. For participants in the Topic condition, the dual-task was preceded by a sentence announcing that the passage would be about washing clothes. To avoid overwhelming the participants, the 68-second passage began after 4 calculations had been completed. At the conclusion of the passage, the participants were asked to write down whatever they could remember from the passage, but these responses were not analyzed, because of the problems involved with using recall as a dependent variable. Results For each participant, the number of correct calculations completed in the dual-task condition was subtracted from the number of correct calculations completed in the single-task condition to Tyler 271 obtain the “WM index score,” where a larger score corresponds to greater WM resource consumption in the dual-task condition. The results are shown in Figure 1. A 2 × 2 (Topic × Language Background) factorial ANOVA revealed significant main effects for Topic (F(1,56) = 6.0, p < .05, ηp2 = .10) and Language Background (F(1,56) = 8.5, p < .05, ηp2 = .13) and a significant interaction between Language Background and Topic (F(1,56) = 4.2, p < .05, ηp2 = .07), showing that the difference in difficulty level between Topic and No Topic was greater for nonnative listeners than for native listeners. It is also interesting to look at the difference between native and nonnative listeners in the Topic condition. A t-test of this comparison, with the alpha rate adjusted to .01 because the test was post hoc, revealed that the difference was not significant (t(28) = .68, p > .5), showing that the difficulty index score was the same for natives and nonnatives in the Topic condition. Thus, processing difficulty seems to be equivalent in the Topic condition for native and nonnative listeners. There was also no significant difference between the scores for native listeners in the Topic and No Topic conditions (t(28) = .29, p > .7). Figure 1. Working memory index scores for native and nonnative listeners in the Topic and No Topic conditions. Error bars represent 95% confidence intervals. 272 Language Learning Vol. 51, No. 2 Extraneous factors that may have affected the results need to be investigated. There was a difference between nonnatives in the Topic and No Topic conditions on their length of stay in Australia. However, there was no significant correlation between difficulty index values and length of stay (r = –.07, p = .73),1 so the difference between Topic and No Topic cannot be attributable to this imbalance. There was also an imbalance of language background between the Topic and No Topic conditions. Takano and Noda (1995) showed that the Foreign Language Effect was enhanced by interlanguage dissimilarity, so the imbalance of participants from Asian and European language backgrounds may have affected the results. In the Topic condition, there were 11 participants from European language backgrounds, but only 3 participants from Asian language backgrounds (see Table 1), and a t-test with these numbers would grossly violate the assumptions of the t-distribution. On the other hand, in the No Topic condition, where the difference between Topic and No Topic was most pronounced, the distribution of languages was balanced, with 7 people from Asian language backgrounds and 8 from European language backgrounds. A t-test was performed and no significant difference was found (t(13) = –.426, p = .68). Therefore, the results of the experiment can not be attributable to the imbalance of language backgrounds between the nonnative participants in the Topic and No Topic conditions. Discussion The results support the hypothesis. There was a significant interaction between Language Background and Topic, demonstrating that the difference in WM consumption between the Topic and No Topic conditions was greater for experienced nonnative than native listeners. In other words, access to topic seems to have had a small effect on the scores of native listeners, but a large effect on the scores of nonnative listeners. From Figure 1, it can be seen that there was only a small difference between natives and nonnatives in the Topic condition, and a post-hoc t-test showed that Tyler 273 this difference was not significant. Thus, when the topic of the Washing Text was available, the WM consumption of nonnatives, as measured by the WM index score, was no different from that of natives. On the other hand, when the topic was unavailable, nonnative WM consumption was greater than that of natives. These results are consistent with the idea that experienced nonnatives not only tend to speak with an accent, but they also hear with an accent (Jenkins et al., 1995). That is, the low-level processes used by nonnative listeners to decode the speech signal, which provide input for the formation of a mental model, are either inappropriate for the target language, or not as efficient as those used by native listeners. For example, the processes may be underdeveloped, as suggested by Wolff (1987); they may consume more WM resources; or they may be qualitatively different from native processes (Bley-Vroman, 1989, 1990). When the topic was unknown, the listeners needed to rely solely on information from the speech signal for comprehension, but when the topic was available, less information was needed from the speech signal to adapt an existing mental model to fit the described situation. That is, even if nonnative language processes are not as efficient as native processes, when the topic was available, nonnatives could still attend to the passage using a similar amount of effort as natives, because less information was needed from the speech signal for the formation of a mental model. By extension, in everyday situations, nonnatives would not be expected to experience comprehension difficulty through WM resource limitations, because most daily situations are predictable, and topic knowledge can no doubt be used to aid comprehension. Difficulty in comprehension would only be expected in unfamiliar situations, where topic knowledge is unavailable. As a consequence of this, it is predicted that experienced nonnative comprehenders have welldeveloped strategies for extracting topic information from situations to assist in comprehension. For the native listeners, it is interesting to note that there was no significant difference between WM index scores in the Topic and No Topic conditions. This means that, on average, the 274 Language Learning Vol. 51, No. 2 reduction in available WM resources between baseline and dualtask was the same for natives in the Topic and No Topic conditions. There are several possible explanations for this finding. First, it could reflect the sensitivity of the dual task for indexing WM consumption. Perhaps the verification of single-digit calculations is not sufficiently demanding to reveal a difference between the native Topic and No Topic groups, even if one exists. Even if this is the case, it is not problematic for the present study, because an interaction between Language Background and Topic was predicted and obtained. It is not the differences between pairs of groups which are important, but the overall relationship among the four groups. Nevertheless, the incorporation of a larger number of passages, ranging in difficulty, could perhaps be included in future studies, because the difference between native Topic and No Topic should vary as a function of passage difficulty. Second, it may reflect different listening strategies for the natives and nonnatives. It is possible that the presence of the dual task changed the way in which the participants comprehended the passage, and this may have exerted a differential influence on nonnatives than on natives. For example, in the No Topic condition, natives may have been content to concentrate on the sentence level, whereas nonnatives may have striven to find coherence in the discourse. Even if this is the case, the results may still reflect differences in low-level processing. Nonnatives may need to focus on the discourse level to compensate for their less developed low-level processes. Third, there could be an effect of anxiety. Nonnatives in the No Topic condition may have been more susceptible to language anxiety than their native counterparts, and this may have been exacerbated by the demands of the dual task. The inclusion of a larger number of passages would also help to address this possibility. If language anxiety is responsible for the effect observed in the present study, then the effect should diminish with later passages, as the participants become accustomed to the task. Language anxiety might also be reduced if a method were used that does not rely on a dual task. On-line methods that also index resource consumption, and that could be adapted to suit the Tyler 275 present experiment include pupillometry (Hyönä, Tommola, & Alaja, 1995; Just & Carpenter, 1995), event-related potentials (ERPs) (Raney, 1993), and the auditory moving window technique (Ferreira, Henderson, Anes, Weeks, & McFarlane, 1996). Future research could also examine low-level processing in more detail. The results of the present study suggest that, on average, low-level processes are less efficient in nonnative than native listeners, but the processes that cause the greater WM consumption are unable to be identified using the current experimental design. The results of studies showing poor perception of English /r/ and /l/ by Japanese speakers (e.g., MacKain et al., 1981; Sheldon & Strange, 1982) suggest the possibility that speech perception processes may be a contributing factor. Further studies could attempt to identify those processes that are problematic for nonnative listeners and ascertain whether the same processes are responsible across language groups and across individuals. The main implications of the present study are for foreign language teaching. On the one hand, a student’s poor underlying language processing may be masked by the effects of topic knowledge. That is, if topic is used to aid comprehension, then it may inhibit the development of low-level foreign language processes from controlled to automatic processes. One solution would be to remove the influence of topic from foreign language comprehension, but this would be difficult to achieve, if not impossible. Rather, there are techniques that could be used to develop those low-level processes in isolation, rather than in a discourse context. For example, in the field of foreign language speech perception, Logan, Lively, and Pisoni (1991; Lively, Logan, & Pisoni, 1993) developed a training task that led to an improvement in Japanese listeners’ discrimination of English /r/ and /l/ and also retention of this improvement. The advantage of this task is that it uses real-world exemplars, such as the minimal pairs “grass” and “glass”, rather than phonemes in isolation. Their technique could be modified to accommodate any speech contrast, provided that minimal pairs of that contrast exist in the target language. Furthermore, Hardison (1998) demonstrated, with both Japanese and Korean learners of 276 Language Learning Vol. 51, No. 2 English, that this type of training on words spoken in isolation generalizes to the earlier recognition of words in connected speech. Thus, the incorporation of such training into regular language classes may allow phoneme perception to improve independently of comprehension. In time, these processes may become automatic, thus reducing the working memory requirements of speech perception processes. On the other hand, experienced nonnative listeners seem to comprehend effortlessly in everyday situations, so foreign language graduates may nevertheless perform well using their foreign language even without the development of low-level processes. If a student’s goal is the rapid acquisition of a foreign language, then perhaps it would be more beneficial to teach strategies for the identification and extraction of topic from situations, rather than focusing on the improvement of low-level processes. For example, students could be taught to analyze a situation for nonlinguistic information, which may provide assistance in narrowing down the number of possible discourse topics. This, in turn, would increase the probability that topic could be used to aid the formation of a mental model. There are many people living in foreign language environments who conduct their daily business using a nonnative language. The results of the present study may be extended to suggest that in everyday situations, where topic knowledge is available, comprehension is no more difficult for experienced nonnative listeners than for native listeners. However, if topic knowledge is unavailable, comprehension will be more difficult for the nonnative listeners. This is interpreted to suggest that the low-level processes used in decoding the speech signal are less efficient in experienced nonnative listeners than in native listeners. The application of this finding to foreign language teaching depends upon the goals of the learner. Students aiming for long-term mastery of a language may benefit from such measures as phoneme discrimination training, whereas students who aim for rapid acquisition, such as travellers, may receive a greater benefit from Tyler 277 training in extracting nonlinguistic information from a situation to aid comprehension. Revised version accepted 13 October 2000 Note 1 A single correlation was performed on the nonnative scores, collapsed across the Topic and No Topic conditions, because each separate correlation would be based on only 15 observations. 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