1. 研究目的与意义（文献综述包含参考文献）

1.introduction this chapter is an introduction to the whole thesis, which illustrates the background, the need, the purpose and the structure of the study.1.1 research backgroundvocabulary plays an incomparable role in learning a new language. to some extent, the effect of vocabulary learning determines the effect of language learning. however, in the traditional teaching method, teachers prefer to pay plenty of attention to grammar due to their beliefs that grammar is the core of a language. although grammar is quite crucial to acquire a language, we cannot ignore the importance of vocabulary. wilkins, david a. suggests very little can be conveyed without grammar and nothing can be conveyed without vocabulary (1975). we can see that vocabulary is the cell of language, the carrier of pronunciation and grammar, and the building material of language building.a large number of researchers try to figure out which way is best for vocabulary learning. nagy, herman incidental vocabulary learning. they hold the view that most native language vocabulary is not acquired through deliberate learning, but is likely to be acquired by accident. nation (1990) also proposes two concepts of accidental vocabulary learning and intentional vocabulary acquisition. krashen (1989) suggests language learners can achieve the best learning effect on the vocabulary they have mastered by taking advantage of incidental acquisition strategies and reading is the most frequently-used strategy. krashen also puts forward a famous theory of second language learning which is made up by five main hypothesis: the acquisition- learning hypothesis, the monitor hypothesis, the natural order hypothesis, the input hypothesis, and the affective filter hypothesis. the input hypothesis is the core of his theory and provides an effective way of vocabulary learning by emphasizing the importance of learners cognitive ability, but he fails to make a specific definition of comprehensive input. the involvement load hypothesis proposed by laufer and hulstijin (2001) indicates that vocabulary acquisition is contingent on the three components--- need, research and evaluation involved in the reading tasks. the higher the involvement load, the better the words acquisition. based on the involvement load hypothesis, gai shuhua conducted an empirical study by assigning two groups to complete different reading tasks (2003). the research result accords with the hypothesis. although many empirical studies about the effects of reading tasks on accidental vocabulary acquisition have been conducted and make us achieve a good understanding of the involvement load hypothesis, the empirical studies about testing the validity of this hypothesis, especially at home are not enough. whats more, the reading tasks the researchers design are various, such as judging true or false, filling blanks, making sentences, multiple choices and writing summaries, but no one makes a combination of these tasks: gap filling, summary writing and sentence making and compare the effects of them on vocabulary acquisition. given the above limitations, the current study takes the empirical study method and combines the three tasks to verify the involvement load hypothesis. 1.2 need of the studyvocabulary is the core of language learning, so it is necessary for language learners to master numerous words. the poor method of learning by rote is obviously out-of-date and not effective enough. nowadays, learning words by accident is well accepted by people because it can not only make students remember words easier, but also make the words retention greater. the method teachers use most frequently is the reading strategy, but whether reading comprehension task is most efficient to vocabulary acquisition is still in discussion, hence task-based vocabulary acquisition is always the focus of researches in the field of second language acquisition. although many empirical studies have compared the effects of different reading comprehension tasks on accidental vocabulary acquisition, they havent compared these three tasks in this experiment and which one is most beneficial to vocabulary acquisition still requires discussing.therefore, making a comparison among the three tasks becomes a necessity, which can help students to acquire new words.1.3 research purposesthe current study is aimed to find out which task is most helpful to acquire new words. the purposes of studies can be illustrated from the following two aspects.firstly, in the theoretical sense, the current study aims to testify the involvement load hypothesis by finding out what are the effects of different reading tasks on accidental vocabulary acquisition. in addition, this study enriches the related studies and makes contributions to the area of second language learning. secondly, in the practical sense, figuring out which reading task is most conducive to vocabulary acquisition can provide assistance for teaching. teachers can design the most suitable reading task to help students acquire new words, which is more interesting and effective than traditional method. students also benefit from this method. they improve their reading ability while acquiring new words. 1.4 structure of the studythe whole thesis is divided into five chapters. chapter one introduces the theoretical background of this research, and outlines the need, aims and organization of the study. the review of some theories relevant to the study and a critical summary of previous studies on the incidental vocabulary acquisition in english reading are presented in chapter two. chapter three illustrates research questions, the design of experiment, methodology, implementation and statistical analysis. chapter four discusses the results and explains the previous questions. chapter five summarizes the major findings and implications of the study, it also figures out the limitations and gives some suggestions for the future studies.2.literature reviewthis chapter explains the definition of key words, the theoretical foundation of the study, as well as the previous relevant studies. the strength and limitations of the relevant studies are also illustrated.2.1 the definition of accidental vocabulary acquisitionbefore defining the term accidental vocabulary acquisition, the concept of acquisition needs to be explained. from the linguistic perspective, acquisition means that humans know how to use a language through a subconscious way where they are not intended to learn the grammar and other rules of language but are able to distinguish right rules from wrong rules. for example, children can speak their native language without any instructions while children are exposed to an environment that everyone uses the native language. quite different from learning which is a conscious process, acquisition prefers to subconsciousness.regard to the definition of incidental vocabulary acquisition, researchers havent reach a consensus. nagy, herman and anderson (1985) initially put forward the concept incidental vocabulary acquisition when they make experiments on the first language acquisition of children. since their research, more people notice the research area incidental vocabulary acquisition. later, schmidt (1994) makes a definition of the term incidental vocabulary acquisition, which is acquiring words unconsciously by focusing main energy on other things, such as communicating, reading and listening. in 1998, laufer proposes a couple of opposite concepts: accidental vocabulary acquisition and intentional vocabulary acquisition. the former means that language learners acquire vocabulary by the way while they concentrate on the meaning and information conveyed in the text through reading, which is also called the by-product of reading activity. the latter means learning and remembering words consciously and actively with the intention of understanding vocabulary. wode(1999) also believes that language learning is a by-product of language used by anyone in the classroom, and that the structure of linguistics is not the focus of attention or the goal of teaching strategies. paribakht and wesche (1999) propose accidental vocabulary acquisition occurs when all of the learners attention is paid to other activities, such as reading and listening, instead of acquiring new vocabulary.the definition of accidental vocabulary acquisition has not come a agreement until now, while people usually prefer to accept the definition made by laufer and hulstijn (2001). they explain the term that learners are asked to complete a task involving the processing of some information without telling them ahead of time that they will be tested afterwards on their recall of that information. the current study is also based on the definition made by laufer and hulstijn.2.2 the involvement load hypothesisthe involvement load hypothesis, proposed by hulstijn and laufer (2001) in cognitive and emotional senses, reveals that the retention of new words depends greatly on the amount of three components--- need, search and evaluation in the tasks. the effects of vocabulary acquisition changes with the three indexes change. need belongs to the emotional dimension, which can be considered as the motivation of success. according to the sources of demand, need can be divided into internal need and external need. internal need come from yourself, not others. for example, when you are determined to do something, you motivate yourself to work hard in order to achieve goals. however, external need is made by others. because of others demands or expectations, you need to complete tasks. compared with external need, internal need is more advantageous to success because yourself is the driven force of your goal. in addition, internal need is regarded as a strong need while external need is a moderate need. the other two cognitive factors are search and evaluation. search refers to that you understand new words from looking up in dictionaries or asking teachers. evaluation means assessing. during the process of comprehending an unknown word, learners choose the most appropriate expression they think from some familiar and close- meaning words. like need, evaluation can also be split into strong and moderate evaluation according to different degrees of efforts. strong evaluation is always related to high efforts of output, such as making sentences and translating paragraphs with target words after reading a passage, while moderate evaluation is closely relevant with the given context, for example, doing multiple choices and filling blanks after reading a passage.the three factors can be seen as the indicators of involvement load. however, as controllable variables in researches, they are not necessary to occur in a task at the same time.2.3 relevant empirical studies at home and abroad krashen (1989) analyzes the relationship between second language acquisition and input effect and he proposes the input hypothesis later on. the hypothesis claims that learners acquire a language by receiving linguistic input beyond his or her current inter-language. in this hypothesis, comprehensible input is considered as the most important part for language acquisition through communication. however, krashen states that output and speech production is insignificant for second language acquisition, which is criticized by other researchers.laufer and hulstijin (2001) explore the function of different reading tasks on incidental vocabulary acquisition and put forward the involvement load hypothesis. in their parallel experiments, they design three different reading tasks (reading comprehension with marginal glosses, comprehension plus filling in target words and composition writing with target words) with different involvement indexes. the result indicates that composition writing that includes three factors is the most beneficial to vocabulary acquisition, which supports this hypothesis. gai shuhua (2003) makes an empirical study on incidental vocabulary acquisition of english majors. in her research, she explores the effects of reading purposes and learning strategies on accidental vocabulary acquisition, and the correlation between vocabulary size and vocabulary retention. the results are illustrated with information processing model put forward by mclaughlin (1987), demonstrating retelling text content after reading contributes to more lasting vocabulary acquisition than answering questions after reading, and lexical size make significant effects on accidental vocabulary acquisition. zhao wulong and li yi (2016) make a research about incidental acquisition effects of english vocabulary in different complex reading tasks on the basis of the involvement load hypothesis. by comparing and analyzing vocabulary tests after four sets of complex reading tasks, researchers find subjects who complete translation tasks outperform among the four groups, which also accords with the involvement load hypothesis.2.4 the strength and limitationsits obvious that most of previous studies confirm the involvement hypothesis and enrich the studies in the area of second language learning. however, there still exists defects. first, some studies havent done pretests about the target words, which makes the results less convincing. without the pretest of vocabulary, researchers may be not sure whether the subjects know the target words. researchers must be certain that all target words are new words to subjects. second, although the comprehension tasks involved in these studies are various, the three tasks --- gaping filling, summary writing and sentence making together havent been combined before. the previous studies prefer to make combinations of tasks with each load of tasks is different, while in the current study, the loads of gap filling and summary writing are same. hence, whether the results can testify the hypothesis or not still requires discussing. therefore, the current study does pretests of vocabulary and combines the above the three tasks together to fill the research gap.referencesaiping zhao, language learning,51(3), 539-558.jung, j. . (2020). effects of content support on integrated reading-writing task performance and incidental vocabulary learning.system,93：1-14.krashen, s. (1989). we acquire vocabulary and spelling by reading: additional evidence for the input hypothesis.the modern language journal,73(4)：440-464.nagy, w. e., nchez, ana. (2016). incidental l2 vocabulary acquisition from and while reading.studies in second language acquisition,38(1), 97-130.reynolds, b. l.. (20174). evidence for the task-induced involvement construct in incidental vocabulary acquisition through digital gaming. the language learning journal, 45(4), 466484.sarbazi, mouhammad- reza. (2014). involvement load hypothesis: recalling unfamiliar words meaning by adults across genders.procedia - social and behavioral sciences,98, 1686-1692.sherrie l. nist, carole mohr. advancing vocabulary skills (pp: 156-159). marlton: townsend press. tang, z. . (2020). a review on studies into incidental vocabulary acquisition through different input. english language teaching, 13(6): 89-95.tong shuang. (2012). an empirical study on the effects of different reading tasks on english-majored students incidental vocabulary acquisition. overseas english, 13: 31-32.xu, x. (2010). an empirical study on the effect of task on l2 incidental vocabulary acquisition through reading.asian social science,6(7), 126-131.yang, y. , cao, x. (2020). effects of task involvement load on l2 vocabulary acquisition and their association with language aptitude.the asia-pacific education researcher(4).zhou xiaohong. (2011). the positive effects of reading tasks on incidental vocabulary acquisition. overseas english, 4: 285-288. 鲍贵、吴翼飞（2019），任务类型与英语词汇习得实验研究，《外语测试与教学》，2：41-49。

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韩娅娟、张卫娜（2014），任务投入量对非英语专业学生英语词汇附带习得的影响，《新西部》，36：141-142。

2. 研究的基本内容、问题解决措施及方案

The present study is also based on Involvement Load Hypothesis by designing 3 different reading tasks (gap filling, summary writing and sentence making) with the purpose to answer the following questions. (1) Is doing tasks after reading helpful to learn new words? Whether reading tasks with different involvement loads have different effects on accidental vocabulary acquisition?(2) Do reading tasks with higher involvement loads have more efficient influence on vocabulary acquisition?(3) Do different types of reading tasks with the same involvement loads have similar effects on acquiring novel words?To address the above questions, 60 first- year students who choose English as their second language in Nanjing Tech University have participated this experiment. They were divided into three groups randomly. First, they completed pretests about vocabulary size to test if their English levels resemble. One week later, they were assigned reading tasks according to their groups. At last, they finished immediate vocabulary tests. The data were collected into computer and analyzed by one- way ANOVA in SPSS 25 software.