Thao Phuong Duong<\/strong> Van Huynh Ha Le<\/strong> The present study investigates the effect of task repetition and individual differences on Vietnamese English as a foreign language (EFL) learners\u2019 lexical use and fluency in oral task performance. The study adopts a within-subjects design with forty students performing the same narrative task twice. Students also completed two prior vocabulary knowledge tests (i.e., a receptive size test and a productive level test) and two working memory tests (i.e., a backward-span task and a Vietnamese-version operation-span task). Lexical complexity was measured in two aspects (i.e., lexical sophistication and lexical diversity). Fluency was assessed in terms of articulation rate. Unlike previous studies, our study surprisingly did not reveal an effect of task repetition on lexical complexity and fluency. Interestingly, prior vocabulary knowledge and working memory appeared to be good predictors of learners’ lexical complexity and fluency.<\/p>\n Keywords<\/em><\/strong>: task repetition, lexical complexity, fluency, prior vocabulary knowledge, working memory<\/p>\n Improving speaking proficiency is often one of the primary goals of language learners. However, in foreign language learning contexts such as learning English in Vietnam, opportunities to speak the target language are limited. This has been considered one of the reasons for Vietnamese learners\u2019 struggles with English speaking even in basic conversations (Nguyen, 2011; Bui & Nguyen, 2016). Therefore, research into techniques to facilitate Vietnamese EFL learners\u2019 verbal skills is important.<\/p>\n Research suggests that task repetition is a potential technique to develop oral performance. It has been widely shown that task repetition can foster oral syntactic complexity, accuracy, and fluency (CAF) (for a review, see Bygate, 2018) with the most robust effect found in fluency rather than other aspects (Ellis et al., 2020). Recently, a few studies have started to look at the improvement in lexical complexity in addition to CAF in oral task repetition (e.g., Fukuta, 2016; Khatib & Farahanynia, 2020; Wang, 2014). However, the findings remain mixed, which might be due to differences in the lexical complexity measures applied or the influence of learners\u2019 individual differences, e.g., working memory, as shown in Ahmadian (2013). Yet, how individual differences such as in working memory or prior vocabulary knowledge influence multiple aspects of lexical complexity and CAF remains less explored in oral task repetition, which warrants more studies.<\/p>\n Further, few task repetition studies have been conducted in the Vietnamese context, e.g., a recent study by Newton and Nguyen (2019). Given that task-based language teaching (TBLT) has been officially selected as one of the main teaching approaches in the National Foreign Languages 2020 project (Nguyen, 2017) and Vietnamese EFL teachers have begun to adopt TBLT in their classrooms (e.g., Phuong et al., 2015; Nguyen, Newton, & Crabbe, 2018; Nguyen & Jaspaert, 2021), research into TBLT techniques such as task repetition within the Vietnamese context is worth exploring. This paper aims to explore the impact of task repetition and individual differences regarding prior vocabulary knowledge and working memory on multiple aspects of lexical complexity (e.g., lexical sophistication, lexical diversity) and fluency. Findings obtained from this paper can contribute to task repetition theory and provide significant pedagogical implications for English teaching in Vietnam.<\/p>\n Task repetition, i.e., repetition of either \u201cthe same or slightly altered tasks – whether whole tasks or parts of a task” (Bygate & Samuda, 2005, p.43), has received increasing attention in the SLA field as a useful technique to improve different aspects of oral performance (i.e., complexity, accuracy, or fluency (CAF)). Such improvement is often attributed to speakers\u2019 shifting their attention from a focus on meaning (i.e., what to say) in the first task performance to a focus on forms (i.e., lexical and grammatical forms) in the repeat performance (Bygate, Skehan, & Swain, 2001). Also, as learners can rely on previously conceptualized content and reuse linguistic features encoded in the first performance, they can speed up processes of language retrieval with less effort in the repeat performance (D\u00f6rnyei & Kormos, 1998).<\/p>\n Research has confirmed the robust effect of task repetition on oral fluency (Ellis et al., 2020) but findings on the effect of task repetition on lexical complexity are mixed. While there has been no consensus in defining lexical complexity, recent vocabulary research has often used lexical complexity as an umbrella term to cover several lexical constructs such as lexical density, number of lexical errors, lexical sophistication, and lexical diversity (Kyle, 2020). For instance, Gass et al. (1999) found that task repetition could enhance lexical sophistication. In particular, learners could use a wider range of words and more low-frequency words after repeating the same narrative task three times. Similarly, Kim et al. (2018) found that L2 learners could produce more low-frequency words as well as more words with a higher age of acquisition on the third time of repetition. On the other hand, Fukuta (2016) found that task repetition could lead to improved lexical diversity and lexical accuracy. He showed that when advanced learners repeated the same picture-prompted narrative task after a one-week interval, they could use a broader variety of words and speak more accurately at the second time of repetition. However, despite using the same tasks as Gass et al. (1999), Wang (2014) did not find an effect of task repetition on lexical diversity, which might be due to differences in the learners\u2019 proficiency level (i.e., intermediate vs. advanced) between the two studies.<\/p>\n A few recent studies have started to investigate both fluency and lexical complexity. For example, while Khatib and Farahanynia (2020) found that task repetition improved learners’ fluency but not lexical sophistication and lexical diversity, Fukuta (2016) only reported the effect of task repetition on lexical diversity but not fluency. These findings appear to indicate a trade-off between lexical complexity and fluency. However, as the number of studies remains scarce and the measures vary across the studies, e.g., subjective measures by Khatib and Farahanynia vs. objective measures by Fukuta, how task repetition influences lexical complexity and fluency remains ambiguous and thus warrants further research.<\/p>\n Working memory (WM) is commonly conceptualized as a cognitive system that involves “temporary storage and manipulation of information activities that is assumed to be necessary for a wide range of complex cognitive activities\u201d (Baddeley, 2003, p.233). While Juffs and Harrington (2011) have shown that learners\u2019 WM capacity can regulate input processing, some scholars have shown that there is a link, albeit weak, between learners\u2019 WM and language production. For instance, learners with low WM capacity tend to speak less fluently and less accurately than those with higher WM capacity (e.g., Ahmadian, 2013; Fehringer & Fry, 2007; O\u2019Brien et al., 2006). This indicates that there is a relationship between WM and aspects of L2 oral performance such as fluency and accuracy. However, to the best of our knowledge, very few studies have explored the relationships between WM and lexical complexity in L2 oral performance.<\/p>\n The link between learners\u2019 vocabulary knowledge and L2 oral performance has been widely confirmed in previous studies. For instance, learners with a greater prior vocabulary knowledge tend to speak more fluently and use more low-frequency and diverse words (e.g., de Jong et al., 2012; Uchihara & Saito, 2019). However, most of the studies have focused on either receptive (e.g., Uchihara & Clenton, 2018) or productive vocabulary knowledge (e.g., De Jong et al., 2012; Uchihara & Saito, 2019) rather than both. Recent studies (e.g., Enayat & Derakhshan, 2021; Clenton et al., 2020) have started to explore both vocabulary knowledge aspects but the findings are mixed. Enayat and Derakhshan found that learners with a greater productive vocabulary tended to speak more fluently while those with a greater receptive vocabulary tended to use more low-frequency words. Yet, the researchers only employed experienced raters to assess lexical use and fluency, which makes it difficult to justify the link between vocabulary knowledge and objectively measurable aspects of lexical complexity and fluency. Clenton et al. (2020) found that only productive rather than receptive vocabulary knowledge significantly related to learners\u2019 fluency. Yet, how receptive and productive vocabulary knowledge predicts lexical complexity has not been studied.<\/p>\n The literature review has revealed several gaps. First, task repetition was found beneficial for improving either L2 lexical complexity or fluency, but little research has investigated both measures together. Further, no study has examined the links among vocabulary knowledge, working memory, L2 lexical complexity, and L2 fluency via repetitive tasks. The present study aimed to fill those gaps. The following research questions were formulated to guide the study:<\/p>\n RQ1:<\/strong> What is the effect of task repetition on learners’ lexical complexity and fluency in L2 oral tasks?<\/p>\n RQ2:<\/strong> To what extent do L2 learners’ prior vocabulary knowledge and working memory moderate the effects of task repetition on L2 learners’ lexical complexity and fluency?<\/p>\n The study adopted a within-subjects design with task repetition<\/em> as a within-subjects variable. All participants performed a narrative task and repeated the same task two days later without being advised that the task would be repeated. They also completed two tests of prior vocabulary knowledge and two tests of working memory. The three dependent variables were two lexical use measures (i.e., lexical sophistication, lexical diversity) and one fluency measure (i.e., articulation rate). The scores of two prior vocabulary knowledge tests (receptive and productive) and two working memory tests (backward-span and operation-span tasks) are moderating variables.<\/p>\n Forty Vietnamese third-year university students (aged 19-21, 20 males and 20 females) participated in the study. They study English as a foreign language at the university where the authors are teaching. A call for voluntary research participation was announced to all third-year students. They all had previously completed 6 years of mandatory English instruction from secondary school to high school and A1 and A2 English level courses at the university before participating in the study. Their English proficiency level was expected to range from an A2 to B1 level.<\/p>\n The present study used a narrative task in which participants were asked to describe their most recent vacation trip. The instructions for the oral task were as follows: \u201cOrally describe your recent vacation. You have 3 minutes for preparation with note-taking being allowed and 3 minutes to speak. No other materials are allowed during the task performance.\u201d Three minutes of planning time were assumed to be adequate for task repetition, according to Li, Chen, and Sun’s (2015) findings.<\/p>\n Participants\u2019 prior vocabulary knowledge was tested on two aspects: receptive and productive vocabulary knowledge. We used Nguyen and Nation’s (2011) English-Vietnamese Vocabulary Size Test (VST) to measure the participants\u2019 receptive vocabulary size. The test contains 140 items with samples of 10 items per 14 frequency bands of 1,000 words. The VST is a frequency-based test which aims to assess learners’ ability to recognize the meanings of words amongst the options given. Following Duong et al. (2021a), the present study used the short version of 70 items instead of 140 items as in the orginal version. Our study also demonstrated a high level of internal consistency (Cronbach’s alpha =.87, n <\/em>= 40) of items in the test. An example item in the Vocabulary Size Test is below:<\/p>\n see. They saw<\/strong> it.<\/p>\n a. c\u1eaft We also adopted Laufer and Nation\u2019s (1999) Productive Levels Test (PLVT) to evaluate the participants’ knowledge of productive vocabulary. This is a controlled production test which asks learners to complete the sentence with a word that fits the context and first letter(s) given. The scores obtained from this test are assumed to reveal learners\u2019 ability to produce words at the 2000, 3000, 5000 and 10,000-frequency levels as well as academic words. A good internal consistency was found (Cronbach’s alpha = .94, n <\/em>= 40). An example item in the PLVT is below:<\/p>\n The thieves threw ac_____ in his face and made him blind. (Answer: acid.)<\/p>\n We used a backward-digit span task to evaluate the participants\u2019 working memory. The backward-digit span task is a complex working memory task that examines learners\u2019 ability to store as well as manipulate information. In total, the backward-digit span task has 8 spans with 2 sets per span. Each set consists of sequences of digits ranging from 2 to 8 digits, which were pre-recorded in Vietnamese (see Figure 1). Participants were asked to listen to these sequences and repeat them immediately to the researcher in the reverse order that the digits were presented. Participants had to stop the test if they could not repeat at least one set of digits per span correctly. The total score of the backward span task equals the total number of sets correctly recalled (max = 16).<\/p>\n Table 1. Two Spans, Each Containing Two Sets of Numbers in the Backward Digit-Span Task.<\/strong><\/p>\n
\nLanguage Institute, Van Lang University, Ho Chi Minh City, Vietnam
\n<thao.dp![\"atmark\"](\"http:\/\/www.tesl-ej.org\/atmark.png\")
vlu.edu.vn><\/p>\n
\nLanguage Institute, Van Lang University, Ho Chi Minh City, Vietnam
\n<vanlhhvlu.edu.vn><\/p>\nAbstract<\/h3>\n
Literature Review<\/h3>\n
The Impact of Task Repetition on L2 Oral Performance<\/h4>\n
Individual Differences as Moderating Factors<\/h3>\n
Working memory<\/h4>\n
Vocabulary knowledge<\/h4>\n
Research Rationales and Research Questions<\/h4>\n
Methodology<\/h3>\n
Design<\/h4>\n
Participants<\/h4>\n
Oral Task<\/h4>\n
Prior Vocabulary Knowledge Tests<\/h4>\n
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\nd. b\u1eaft \u0111\u1ea7u<\/p>\nWorking Memory Tests<\/h4>\n