Due to numerous reasons, there are readily noticeable differences and limitations among Chinese school children learning English literature. The Copular verbs in English literature belong to a subgroup of verbs which are special in terms of their semantic features and syntactic functions. The copular verb system in Chinese language is different from that of English. Moreover, since copular verbs seem to be simple and easy, Chinese school children learning English tend to ignore them while using them in spoken and written matters; especially beginners are more inclined to omit copular verbs whether their native Chinese language has an equivalent form or not (Celce-Murcia & Larsen-Freeman 1999). It seems that they often fail to appreciate the importance of syntactic function of copular verbs.

The studies on copular verbs at home country and abroad are mainly focused on the grammatical aspects, classification or the superficial meaning and use rather than the factual use (Jespersen 1928; Quirk 1985; Lei 1995: 30-31; Granger 1998; Li 1998; Wang 1998: 114-118; Chen 1998; Ning 2003: 109-110; Zhao and Huang 2001: 1-6).

Biber (2000), is one of the pioneers who studied the distribution of copular verbs in light of their factual use based on the Longman Spoken and Written English Corpus.

Liu Hua (2004) studied the semantic meaning and use of copular seem by analyzing the concordance lines in FLOB. But the corpora used in these studies are native corpora rather than learner corpora.

There are scanty references available about any systematic and in-depth research about the status of copular verbs used by Chinese school children learning English in China and abroad. So, present corpus-based study on the copular verbs as used by Chinese school children learning English in these two countries might be useful to evaluate current status of copular verbs as used by Chinese school children, which may show long term effect on the spoken and written English literature developing in China.

The word copula originates from the Latin noun for a "link or tie" that connects two different things. Grammarians and linguists use a great variety of terms such as “copulative”, “intensive”, “linking” or “link” verbs for the phenomenon (see Jespersen 1933; Lyons 1977; Huddleston 1984; Quirk et al. 1985; James 1998).

Copular verbs can be classified differently according to different standards. The copular verbs, the authors studied in this research, are classified into four groups according to Quirk et al. 1985;: (i) be, the principal copular verb; (ii) “verbs of seeming” including seem, appear, and the perception verbs look, sound, etc; (iii) “verbs of remaining” including remain, keep and stay. (iv) the resulting copular verbs are in the main “verbs of becoming” such as come, get, go, grow, turn, prove and some copular phrasal verbs end up, turn out, and wind up.

So far, there is no general agreement as to the form and function of the element following copular verbs. But it is commonly agreed that adjective phrase, noun phrase, pronoun, prepositional phrase, adverb and obligatory adverbials are popular elements after copular verbs.

By adopting corpus-based approach in this research, we aim to probe into the use of copular verbs in Chinese college English learners' writing through a comparison between learners' corpus and native speakers' corpus. The main research questions are the following:

• Is there any difference in the overall frequencies of the use of copular verbs between Chinese English learners and native speakers?
• Is there any difference in the selection tendency of copular verbs between Chinese English learners and native speakers?
• Is there any difference in the use of complement after copular verbs between Chinese English learners and native speakers?

The learner corpus used in this research is the College Learner English Corpus (COLEC), the sub-corpus of the Chinese Learner English Corpus (CLEC). LOCNESS, the control corpus in this research, is the abbreviation of the Louvain Corpus of Native English Essays, a sub-corpus of the International Corpus of Learner English (ICLE).

With the aid of Wordsmith, the researchers search copular verbs one by one in the two corpora respectively, and get the frequencies and the textual information. What should be noted is that the inflectional forms of each copular verb are also counted. After the retrieval of each copular verb, delete those concordance lines in which the search word does not function as copular verb according to the identification criteria of the copular construction. For example, be is used as the auxiliary or feel is used as a transitive verb or feeling as a noun, etc.. Then label each concordance line to differentiate different complement after each search word and Wordsmith helps to resort them and the raw frequencies can be provided. Since the sizes of the two corpora used are different, all the frequencies are computed into normalized frequencies (occurrences per 500,000 words) in order to arrive at comparable frequencies across corpora of different size. The last step is data processing and analysis. By comparing the frequencies and analyzing the textual use of copular verbs, the researchers try to discover the differences in using copular verbs between Chinese college English learners and native speakers.

In the overall frequencies, there is difference in the use of copular verbs between Chinese college English learners and native speakers. The former use less copular verbs than the latter (15,068<22,411; 3.01%<4.48%). Native English speakers use 1.47% more copular verbs than Chinese English learners (Table 1). But from this data, the researchers cannot definitely conclude that Chinese English learners use fewer copular verbs than native speakers because they do not know whether the overall frequency of copular verbs in the COLEC is significantly different from that in the LOCNESS. So a Chi-square test significance test was employed (Table 2 and Table 3).

The result of Chi-square Test for the overall frequencies of copular verbs in the two corpora in Table 4 shows the P value lower than 0.05( < 0.05 ), which means there is a significant difference between Chinese English learners and native speakers in the overall frequencies of copular verbs used in their written matters. Hence the researchers concluded that there is a general tendency of under using copular verbs in Chinese English learners' written matters.

Table 1. Overall frequencies and percentages of copular verbs in the COLEC and the LOCNESS

Table 2. Distribution of each copular verb in the COLEC and the LOCNESS

Table 3. Chi-square test for the comparison of overall frequencies of copular verbs in the two corpora

Table 4. The Chi-square test for the frequencies of copular verbs in the two corpora

As far as the individual copular verbs are concerned, overuse and underuse co-exist (Table 4 which shows that the verbs in the table represent their different forms). Most of the copular verbs, such as be, seem, become, remain, feel, sound, prove, grow, go and stay follow the general tendency of under using by Chinese English learners; and the Chi-square tests in Table 4 show that the differences are all significant with the P value .000 except grow (P=.002), prove (P=.002), go (P=.025) and stay (P=.012) with a little higher P values. While look and keep are significantly overused by Chinese college English learners with the P value .000. < .05). But after the close examination of the concordance lines, we find that among the 58 occurrences (raw frequency) of look as copular verb, the adjective phrase upset and depressed as the subject complement of look appears 42 times. And the 54 occurrences (raw frequency) of keep as a copular verb in the COLEC, the subject complements following keep are all adjective phrases, and out of the 54 adjective complements, the adjective fit appears 40 times. This, to a large extent, is caused by the topics and the directions of the compositions in the examination. If these lines are excluded, it is obvious that look and keep are underused, too. Though Chinese college English learners use fewer turn out and come than native speakers, the difference is not significant (P = .170 > .05) either. On the contrary, get and taste are overused by Chinese college English learners, but the difference is not significant either (get: P=.118, taste: P = .414). So in the frequencies Chinese college English learners use the copular verbs get, come, turn out and taste similarly with native speakers. And for the copular verb turn, there is no difference at all, because it has the same occurrence in the two corpora. As for smell which does not appear in LOCNESS at all, appear, end up and wind up which have no occurrence in COLEC will not be compared in this study. Therefore, a conclusion can be drawn that there is a general trend of under using of copular verbs by Chinese school children learning English compared with the native speakers.

Generally speaking, there are both similarity and difference in the selection tendency between Chinese students learning English and native English speakers (Table 5). First of all, copula be is overwhelmingly the most frequently used in the two corpora since the percentage of copula be among the overall frequencies of all the copular verbs studied here is 90.73% in the COLEC and 88.17% in the LOCNESS. Secondly, the five most frequently used copular verbs (be, become, get, seem and feel) in the two corpora are almost same except get and seem. Get is the third frequently used copular verb in the COLEC but the fifth in the LOCNESS. While seem is the fifth in the COLEC but the third in the LOCNESS. This means that both Chinese English learners and native speakers tend to choose be, become, get, seem and feel. But Chinese English learners use more get than native speakers while native speakers use more seem than Chinese English learners. Thirdly, both Chinese English learners and native speakers seldom use smell, end up or wind up. Fourthly, the orders of some of copular verbs such as sound, go, grow, prove, stay and turn in the two corpora are quite similar. Finally orders of the rest copular verbs appear, remain, look, come and keep in the two corpora are quite different, the taxes differences reach four to nine taxes.

Table 5. Comparison of selection tendency of copular verbs in the two corpora

It has been known to us from Table 5 that copular verbs as a whole was underused by Chinese English learners. Among the copular verbs the researchers study, three copular verbs do not appear in the COLEC at all. And more than ninety percent copular verbs used by Chinese English learners are the copula be, other copular verbs take less than 10%. So the researchers conclude that Chinese English learners select a limited variety of copular verbs. The possible explanation is that Chinese English learners tend to use copular verbs they are familiar with and avoid using what they are not familiar. From the language-learning point of view, this is error avoidance strategy that learners adopted in the process of language learning.

After the study of the concordances, it is found that types of complement after most copular verbs used by Chinese English learners lack variety. For example, the complement after the copular be are mostly adjective phrase and numeral in the COLEC with a higher percentage than that in the LOCNESS, while the percentages of the noun phrase, nominal clause, prepositional phrase, pronoun, adverb as complement and ellipsis of complement are all significantly lower in the COLEC than that in the LOCNESS. Take the copular verb feel as another example. Except one case of feel followed by prepositional phrase all the concordance lines extracted from the COLEC are feel + AdjP. For the LOCNESS, that is quite different. Except feel + AdjP, feel + as if / as though clause, feel + PreP and feel +like + NP are also found. The use of the copular verb sound is more typical. Among the seven concordance lines extracted from the COLEC, the researchers find that all of them are used in the construction of sound + AdjP. But the use of copular verb sound in the LOCNESS is rather different. The use of become is also the case, almost 60% of complement after it are adjective phrase and more than 35% are noun phrase with pronoun, prepositional phrase and clause as complement occur in the LOCNESS having no occurrence.

After a further study of the complement in the concordance lines of each copular verb, the researchers find that the complement of copular verbs in the COLEC are less various and more simpler than that in the LOCNESS. Just take the copular be as an example, most of the prepositional phrases after be are fixed phrases with the preposition in like “in trouble”, “in a hurry”, “in emergency”, “in need of”, “in good/bad mood”, “in good/bad health”, “in a rage” etc. Some of them indicates time or place, for example, “in 1990”, “in high school”. There is only a small amount of lines containing the phrases with other prepositions. On the contrary, the prepositional phrases functioning as subject complements or obligatory adverbials in the LOCNESS are formed with a large range of prepositions like in, at, on, through, by, with, without and because of etc. Compare the concordance lines in Table 6 and Table 7 which are from the COLEC and the LOCNESS respectively, we can see the complements in the COLEC are rather simple, either an adjective or a numeral or a preposition, while the complements in the LOCNESS are always some phrases even clauses.

Table 6. Sample concordance lines of subject complement of copular verbs in the COLEC

Table 7. Sample concordance lines of subject complement of copular verbs in the LOCNESS

Factors contributing to Chinese English learners' use of copular verbs are multifold. First of all, mother tongue transfer is one of the most important factors. Copular verbs in Chinese always link two noun phrases (Zhang 2002: 50). For some expressions like “This idea sounds / is good”, “He grows old”, “You are high, but he is short”, “He is / seems / appears angry”, “The milk went sour”, there is no copula verb used in Chinese: “zhe zhu yi bu cuo”, “ta lao le”, “ni gao ta ai”, “ta sheng qi le”, “niu nai suan le”. Influenced by mother tongue, Chinese English learners may omit the copular verbs needed in English. This may cause the underuse of most of copular verbs by Chinese English learners. Secondly, copular verbs are seemingly so simple that language teachers and teaching materials provide little information about this subgroup of verb. And the information provided is different from that in the native corpora (Liu Hua 2004: 427-432). Therefore teaching transfer may cause Chinese English learners to neglect copular verbs and result in the underuse. Thirdly, the standardized type / token ratio (the COLEC is 31.65%; the LOCNESS is 40.00%) reveals that Chinese English learners have mastered less vocabulary than native English speakers. This may result the less variety and less complexity of copular complement in the COLEC. Fourthly, Chinese English learners seem to lack a full understanding of some copular verbs, especially their hidden and slight differences in meaning. Lastly, strategy transfer, register awareness and so on may be the factors contributing to the observed differences.

From the point of view of learning foreign language or teaching , the findings of the present research shed light on the essential areas of problems for the learners in the acquisition of copular verbs and difficulties faced by the teachers during the process of teaching.

Teaching and learning materials for example the textbooks and dictionaries should be adjusted to present Chinese English learners more native corpora so that learners may have a true picture of the use of copular verbs by native speakers. The learner corpus in particular serves to help the learners raise self-consciousness of their own language use (Li, 1998: 82), while the native corpora could provide the norm of the target language for the English learners. To master a word is not only to know the basic meaning but we need to learn the hidden and implied meaning, and also to distinguish the words that have the similar meaning or uses. English teachers should urge their students not only to get to know the meanings of copular verbs, but to use the copular verbs appropriately. For example, the distinction between the written English and the colloquial English should be emphasized by teachers and should be included in the study materials provided. According to Liu Xingbing (2005: 109-112), the English Syllabus for school students doesn't emphasize this point at all. No wander that English learners will feel less confidant and get confused by this kind of subltle/ hidden meaning of several other English words and inadertantly make mistakes. For the learning of English copular verbs, the better way for Chinese English learners is to be exposed in the native corpora so as to learn them in the context and differentiate the subtle difference of meaning and use between the interchangeable ones. Current study shows that there is a strong possibility for long term effect of such anomales on the future generation English literature of the Chinese community in general. We may therefore extend this kind of research study among the Chinese community residing abroad like Taiwan, Hongkong, Singapore, Malaysia, Myanmer etc , and make a comparative study in depth to appraise the relevant differences with the mainland Chinese school children learning English.