Introduction

As we all know, during the whole process of foreign language learning, vocabulary learning plays an extremely significant role. It is one of the essential components of a language is the unity of meaning and structure in the language system. One of the main difficulties for those EFL learners who want to achieve effective communication is the amount of words they need to acquire. Vocabulary size directly influences L2 learners mastery and application of the four basic English skillslistening, speaking, reading and writing. So far much research has done on incidental L2 vocabulary acquisition in the field of reading(Gai, 2003; Huang, 2004; Hulstijin Laufer, 2001). But little has been done on the effect of task type on EFL learners single word acquisition. This study is aimed to apply the involvement load hypothesis to investigate the two typesmultiple choice and cloze affect EFL learners incidental single word acquisition in listening.

Pedagogically, vocabulary is the base of any language, which is used to make up large structures like sentences, paragraphs and even whole passages. The acquisition and retention of single words have become one of the critical issues in second language learning and teaching. Because L2 vocabulary is critical important to L2 learners and teachers, facilitating learning and teaching L2 vocabulary requires studies concerning how various factors affect L2 vocabulary acquisition.

Theoretically, incidental vocabulary acquisition has become one of the focuses in the study of second language vocabulary acquisition. Those research achievements made by researchers from China and overseas not only improved public awareness towards the effectiveness of incidental vocabulary acquisition, but also broadened the thought of second language vocabulary teaching. Many researchers are interested in incidental L2 vocabulary acquisition through reading, and their studies are based on the involvement load hypothesis (Hulstjin Laufer,2001; Wu, 2010; Huang, 2004), and also the input frequency hypothesis (Brown, Waring, Donkaewbua, 2008; Vidal, 2003, 2011) and input-output hypothesis (Lei, 2011; Wang, Yao, Xu,2012). However, rare research was explored on whether the involvement load hypothesis, the input-output hypothesis and input frequency hypothesis can explain the incidental L2vocabulary acquisition through listening.

This research aims to see how the involvement load hypothesis contribute to incidental L2 vocabulary acquisition through listening. Hoping the findings of the research are valuable to EFL learners and teachers in the aspect of vocabulary learning and teaching by offering them some useful suggestions.

Literature review

Usually, second language vocabulary acquisition includes acquiring intentionally and incidentally by whether learners focus their attention on the word or not. The concept of incidental vocabulary acquisition was defined by Nagy, Herman and Anderson in 1985 on the basis of a study on childrens native language acquisition. It means that students attention is not on remembering new words but they remember them unconsciously when they are doing other tasks, like reading and communication (Schmidt 1994:165-210). According to Nagy et al. (1985), a big number of first language vocabulary knowledge children acquired is neither by consulting dictionary, nor from the formal classroom instruction, but gains in their daily life, such as communicating with others, reading stories, listening to radios and watching TV series and so on. Brown et al. (1999) pointed out that the term of incidental vocabulary acquisition can also be applied in second language acquisition. Wesche and Paribakht (1999) indicated that incidental vocabulary acquisition happens when learners focus on the meaning of the text they read, and not when pay attention to unknown words.

Hulstjin and Laufer (2001) thought the incidental acquisition as by-product of reading and listening activities not merely focus on vocabulary learning. As relative to incidental vocabulary acquisition, Hulstjin and Laufer (2001) stated that intentional vocabulary acquisition as the move aimed at purposely memorizing lexical information and making that information be accessible to read. Hulstjin and Laufer (2001) argued old in advance that in experiments investigating incidental vocabulary learning, learners are typically required to perform a task involving the processing of some information without being told in advance that they will be tested afterwards on their recall of that information. In contrast, participants in an intentional learning situation are told in advance that their recall will be tested afterwards (p.10).

Whether participants attention is on vocabulary or not (Wesche Parbakht, 1999), and whether the participants are told of the upcoming vocabulary test before learning(Eysenck, 1982) differ incidental second language vocabulary acquisition from intentional second language vocabulary acquisition on the basis of the experiment many researchers conducted.

In conclusion, when learners are busy with some other activities (reading, listening, writing and speaking), and there is no intention to learn new word but acquired new words incidentally-- this is how incidental L2 vocabulary acquisition takes place.

With regard to incidental vocabulary learning, (Laufer, B., J.H. Hulstijn, 2001) tentatively proposed the notion of the Involvement Load Hypothesis. This hypothesis has been developed based on the depth of processing model, which was first proposed by (Craik, F.I.M., R.S. Lockhart,1972). They recommended that retention in the long-term memory depends on how deeply information is processed during learning. Involvement is perceived as a motivational- cognitive construct, and retention of unfamiliar words is claimed to be conditional upon the amount of involvement while processing these words. (Laufer, B., J.H. Hulstijn, 2001) propose that the construct of involvement is composed of three components: need, search, and evaluation.

Need, as the motivational, non-cognitive dimension of involvement, is concerned with a drive to accomplish the task requirements, imposed either internally or externally, which is also used to distinguish between moderate and strong need. According to (Laufer, B., J.H. Hulstijn, 2001), need can occur in two degrees of prominences: moderate and strong. Need is hypothesized to be moderate when it is imposed by an external agent, for example, when the teacher asks students to use a word in a sentence. Need is strong when it is intrinsically motivated and self-imposed by the learners, for instance, when learners decide to look up a word in a dictionary while writing a composition.

Search is the attempt to find the meaning of an unfamiliar L2 word by consulting dictionaries, or the attempt to find the L2 word from expressing a concept by asking a language teacher, for example, trying to find the L1 translation of an L2 unknown word by looking it up in a dictionary. Although need has two degrees of prominence, i.e., either moderate or strong, there are two degrees of prominence for search. It is either present with index 1 or absent with index 0. When the meaning of an unknown word is given, that is, the attempt of search is not required, search id absent.

Evaluation entails a comparison of a given word with other words, a specific meaning of a word with its other meanings, or combining the word with other words in order to assess whether a word does or does not fit its context. Evaluation comprises of two potential degrees of cognitive processing: moderate and strong. Evaluation is moderate when learners must recognize differences between words provided in a given context (e. g. deciding which meaning of the target word best fits the context in which it is encountered) and strong when the task requires making decisions about new words and combining them with known words in original contexts (e. g. sentence and composition writing).

According to Hulstijn and Laufer (2001), when testing the effect of task-induced involvement on incidental L2 vocabulary acquisition, the task with higher involvement load contribute better vocabulary acquisition than the task that induce lower involvement load. Furthermore, tasks inducing the same amount of involvement load result in the same vocabulary acquisition. As they claimed, retention of unknown words was determined by the degree of involvement while processing words.