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Literature review

The effects of different tasks are manifest in vocabulary acquisition. It means that the ability of vocabulary acquisition can be improved by a variety of tasks.

Generally speaking, the main related tasks are below: reading comprehension and the listening input frequency.

In a series of studies (Nagy et al. 1985; Nagy et al. 1987; Nagy and Herman 1985, 1987), Nagy and his colleagues defines theory which is widely accepted today in both first and second language acquisition. Central to their theory is that incidental vocabulary learning is a gradual process in which gains are made in small increments with repeated encounters needed to gain full knowledge of a word.

In fact, several researchers in the field of vocabulary acquisition (Laufer, 1991, 1997; Nation, 1993; Ridgway, 1997; Smith, 1998) found that vocabulary knowledge was closely related to reading comprehension. In reading an English text, vocabulary difficulty has consistently been found to be the most significant predictor of overall readability (Nation Coady, 1988). If vocabulary knowledge is one of the keys to reading comprehension, how many words does an EFL learner need to know then?

Laufer (1991: pp126-132) estimated that the turning point of vocabulary size for reading comprehension is about 3,000 word families. By word families, she meant a base form plus its inflected and derived forms, which increases the total amount to about 5,000 lexical items. In other words, without the basic 3,000 word families, or 5,000 lexical items, ESL/EFL learners are less likely to predict with relative success the meanings of an authentic text. Only when learners have a command of 3,000 word families can they understand about 90% to 95% of the running words of any text.

Lots of literature confirms that reading is feasible and effective for vocabulary acquisition (Nagy et al., 1987; Dupy Krashen, 1993), but little research has been conducted on the relationship between listening and vocabulary acquisition. Only a few studies further discussed that which specific listening condition is more conductive of vocabulary acquisition. Such as Joes (1998) and Wangs (2002) researches in vocabulary acquisition.