Thai EFL Students ’ Writing Errors in Different Text Types : The Interference of the First Language

This study aimed at analyzing writing errors caused by the interference of the Thai language, regarded as the first language (L1), in three writing genres, namely narration, description, and comparison/contrast. 120 English paragraphs written by 40 second year English major students were analyzed by using Error Analysis (EA).The results revealed that the first language interference errors fell into 16 categories: verb tense, word choice, sentence structure, article, preposition, modal/auxiliary, singular/plural form, fragment, verb form, pronoun, run-on sentence, infinitive/gerund, transition, subject-verb agreement, parallel structure, and comparison structure, respectively, and the number of frequent errors made in each type of written tasks was apparently different. In narration, the five most frequent errors found were verb tense, word choice, sentence structure, preposition, and modal/auxiliary, respectively, while the five most frequent errors in description and comparison/contrast were article, sentence structure, word choice, singular/plural form, and subject-verb agreement, respectively. Interestingly, in the narrative and descriptive paragraphs, comparison structure was found to be the least frequent error, whereas it became the 10 frequent error in comparison/contrast writing. It was apparent that a genre did affect writing errors as different text types required different structural features. It could be concluded that to enhance students’ grammatical and lexical accuracy, a second language (L2) writing teacher should take into consideration L1 interference categories in different genres.


Background of the Study
Of the four English skills, writing has been found to be the most difficult for EFL learners to master, especially in Thai universities where English is mainly taught as a compulsory subject, since writing in a second language requires both syntactic and semantic knowledge.Weigle (2002) points out, "The process of text generation, or encoding internal representations (ideas) into written texts, may be disrupted by the need for lengthy searches for appropriate lexical and syntactic choices" (p.36).Clearly understood, the insufficiency of linguistic knowledge or limited language competence has negative impact on writing proficiency as well as L2 writing quality.
Ironically, even though writing is perceived to be the hardest skill to acquire, it is becoming more demanding in the age of entire communication via email and other communicative technologies.Santos (2000) explains that there are three reasons making writing increasingly essential which are 1) more international linguists are promoting writing as their field of specialization, 2) more articles and journals are being published in English, and 3) more international students are pursuing their degrees in English speaking countries.Besides, Chen (2007) states that owing to the age of globalization, the world seems to be smaller because of the perception of unlimited communication.For this reason, all members of global institutions, for their own benefits in terms of education and business cooperation, have to stay connected with one another.In order to comprehensibly express thoughts and opinions, apart from oral interaction, writing is considered crucial.On account of its importance, many colleges and universities thus offer more writing courses, for example, Writing for Specific Purposes, Academic Writing, Paragraph Writing, and so forth to students who need to improve their writing.Silva (2000) notes that a number of second language writing specialists are very much required due to the increasing demands of English writing courses.From Silva's notion, a question like "Why are so many L2 writing specialists needed?" may be raised.To reasonably answer, among four English skills, writing has been perceived as the most difficult to teach as well as to study on account that a writing teacher has to devote considerably more time, energy, and expertise in order to help a group of student writers effectively develop their skills.It can be said that teaching writing is not a simple task because a variety of writing competences, comprising grammatical structures, organization, vocabulary, ability to give feedback and appropriate assessment of students' written works, is highly required as Matsuda (2000) asserts that to help student writers enhance their writing effectiveness, over the last few decades, only the language itself has been considered as insufficient for a writing teacher to focus on in an L2 writing environment.Therefore, it can be clearly seen that even the teaching of writing is not that easy, so how is it going to be simple for such learners, especially for those speaking other languages but English?
In the Thai educational context, the importance of writing has been realized since many universities provide writing courses, as both elective and compulsory subjects, for students to register.To clearly illustrate, according to the curricula of Thepsatri Rajabhat University, English major students have to pass four English writing courses in order to graduate: Paragraph Writing, Writing for Specific Purposes, Writing Strategies in English, and Creative Writing.Yet, the students' writing ability is still far from satisfactory.In an attempt to help Thai EFL learners improve their writing skills, many research studies have been conducted.For example, some studies focus on writing problem identification so as to categorize error types frequently made by student writers at both sentence and paragraph levels (Sattayatham & Honsa, 2007;Sattayatham & Ratanapinyowong, 2008;Jenwitheesuk, 2009), while others emphasize particular approaches that assist L2 writers to increase their writing accuracy, many of which are related to teacher feedback and peer revisions (Torwong, 2003;Kaweera & Usaha, 2007;Wang & Usaha, 2009;Ho & Usaha, 2011).To become effective writers, students have to devote a great deal of time and effort to continuously practice writing, which makes them feel depressed and finally give up on writing accomplishment.Meanwhile, writing teachers often suffer from a greater workload, having to read and correct the paragraphs and essays produced by students.This is thus perceived as a genuine problem that needs solutions.
The following piece of writing taken from a student's paragraph illustrates the challenge of comprehensibility: To travel to Chanthaburi with a teacher and friends, First, go sightseeing aquatic animals museum at the King Ka Ben, there are a lot of aquatic animals various kinds such as anemone fish, whale, shark, Siamese tiger fish and ray.Second, lists the narrate and the method grows mangrove forest and get see animals in the mangrove forest such as mudskipper, meder mangrove carb and blue swimming crab.Finally, have a swim with friend in the sea at the Chao Lao beach.In the evening have a meal dinner and have the singing play and dance merrily.This travel is the travel that remember most because , be the travel has that to travel with my friends before ends high school and the travel that is advantages and learn the news know, be good travel and impress for I.

(A paragraph on "My Memorable Trip" written by a Thai university student)
From the above paragraph, a lot of misuses of vocabulary and grammatical structures can be seen, all of which make the story difficult to follow.In terms of organization, the student seemed to understand how to use transitional markers like first, second, and finally to organize her thoughts.However, the syntactic structures were her main problems, failure to use simple past tense verbs to tell her story, no pluralizers for plural nouns, subject omission, direct translation, and the use of pronouns, for instance.It was apparent that she transferred her L1 syntactic properties in her L2 writing, which caused such errors.That is to say, the mother tongue, at times, interfered with the student's L2 writing, which eventually reduced her writing effectiveness.

Statement of the Problem
In the last decade, a good number of studies conducted have proved that the interference of the mother tongue is a severe problem in EFL and ESL writing contexts.Bhela (1999) investigated L1 interference in L2 writing.The participants, a Spanish, a Vietnamese, a Cambodian, and an Italian student, were asked to write stories, using provided pictures.The findings indicated that the learners, due to their L1 influence, produced ineffective written stories with inappropriate structures.In order to express thoughts, they made use of L1 syntactic properties and related them to L2 structures, which caused errors in some extents and eventually led to the gap between L1 and L2 linguistic features.Camilleri (2004) studied the native transfer in Maltese students' English writing.A hundred essays written by selected participants were examined to detect errors caused by L1 interference, based on five stages of investigation comprising data collection, error identification, error description, attribution of error categories, and reflections on the findings.The results revealed that the errors most frequently made by the students were classified into 13 categories, namely noun, adverb, verb, adjective, verb form, preposition, article, spelling, concord, idiom, pronoun, passive voice, and word order.The causes of errors found were mainly from the interference of L1 in relation to the direct translation, the differences of syntactic properties between L1 and L2, and the transfer of L1 systems in L2 writing.Hyland and Anan (2006) examined teachers' perceptions of errors caused by L1 interference in L2 writing.Sixteen participants were divided into three groups: native English speaking teachers, Japanese speaking teachers, and native English speaking non-teachers.They were asked to correct a text written by a Japanese college student in order to see what types of writing aspects were considered the most severe problem.It was found that the native Japanese speaking teachers put much emphasis on grammatical structures in the student's writing.They regarded the violation of the syntactic rules as errors because these students would at times employ the structures of the Japanese language when writing, which caused a number of errors.As a result, the interference of the mother tongue was seen by Japanese teachers as a crucial factor requiring urgent correction.On the other hand, the native English speaking teachers emphasized formality and appropriateness of academic competency.It was also explained that due to the different experiences between the three groups of participants, the Japanese teachers viewed grammar accuracy as an initially essential aspect that made a good piece of writing.
Similar to the aforementioned research in various contexts, many studies have found that L1 interference in L2 writing is also perceived as a serious problem among Thai EFL writers.Sattayatham and Honsa (2007) examined writing and translation errors made by first year medical students at a Thai university.The participants were asked to translate and write paragraphs in English.The completed tasks were analyzed so as to identify ten most frequent errors, which were wrong choice of vocabulary, articles, wrong plural form, wrong use of very "to be", conditional sentences, punctuation, connector, fragment, subject-verb-agreement, spelling mistake, and omission of subject, respectively.The study concluded that the students made such errors when translating and writing in English because they were dependent on the systems of the Thai language.Most of them were related to syntactic and semantic properties.Likewise, Jenwitheesuk (2009) investigated the causes of L2 writing errors in third year college students' written works.The study revealed that their errors were mainly caused by a lack of syntactic knowledge.The four most frequent errors found were determiners, subject and verb agreement, tenses, and prepositions, respectively.It was thus explained that due to the limited grammatical and lexical competence, the students relied on their first language systems and transferred them into L2 writing.The researcher claimed, "the persisted errors in writing were resulted from the mother tongue interference, the false hypothesis and the ignorance of the correct sentence patterns of English structures, together with the lack of knowledge in grammatical rules" (p.982).
In brief, with regards to some studies as illustrated, it is apparent that errors caused by L1 interference have been seen as an unavoidable obstacle that all EFL and ESL student writers have to encounter, resulting in ineffective L2 writing.As a result, for decades, it has become an attractive issue that many language researchers have studied in order to find out what approaches and methods can really assist L2 writers to overcome this difficulty.Interestingly, even though there have been studies on errors caused by L1 interference in university students' English writing, there has been no research into the types of errors and interference in different writing genres.This study has, therefore, focused on the identification of English writing errors found in three different writing genres (narrative, descriptive, and comparison/contrast) in order to test the claims that each genre has particular types of errors, and consequently that when teaching students to write English paragraphs, a teacher has to consider the types of errors, expected to be made, according to each particular genre.To do this, an appropriate emphasis can be put on the right grammatical structures during the process of writing revision, which helps student writers enhance their writing accuracy.

L2 Writing Difficulty
Of the three elements of writing, content, organization, and language, it is fair to say that language has been considered the most problematic difficulty for L2 writers due to their limited language proficiency or limited linguistic knowledge.Silva (1993) explains that inadequate language knowledge, at times, leads to ineffective L2 writing on account of the differences between first and second language.Olsen (1999) notes that some EFL writers cannot create an effective written work due to the inadequacy of syntactic and lexical competence, which at times makes them confused with the systems of the target language they are learning.Besides, to quote Weigle (2002), "because of the constraints of limited second-language knowledge, writing in a second language may be hampered because of the need to focus on language rather than content" (p.35).She also claims that it is impossible for L2 students to write in a second language properly without linguistic knowledge regarding grammar and vocabulary.That is, L2 writing can be more difficult if syntactic properties of the two languages are very different, which makes L2 students rely on their first language when writing in a second language.
According to Wang and Wen (2002), L2 writers obviously get stuck when writing in the target language (TL) because their mother tongue majorly affects the use of the second language; consequently, they may at times combine the systems of the two languages in their L2 writing, which is called "language transfer or syntactic transfer".This is considered a severe problem of L2 writing as Fromkin et al. (2003) clarify that L2 learners are so dependent on their L1 syntactic properties that they transfer some L1 grammatical rules in their L2 writing, eventually causing such errors.In order to comprehend L2 writing difficulty in terms of language and syntactic transfer more clearly, a number of researchers as well as scholars have paid much attention to identifying what hardships L2 student writers may confront while writing.Chan (2004) investigated the evidence of syntactic transfer from Chinese into English.The data obtained from 710 Hong Kong Chinese students were to be analyzed.The students were asked to translate provided sentences in English and to correct 20 ungrammatically written sentences, using their own language judgment.The focus of L1 interference was on five categories: copula control, adverb placement, inability to use there is, failure to use relative clauses, and confusion in verb transitivity.The results showed that the extent of syntactic transfer was most often employed by the learners of a low proficiency level.That is, the learners at this level relied much on their L1 syntax and lexicons, which they resorted to when writing in the second language.Thep-Ackrapong (2005) points out, "English and Thai are different at all levels: pronunciation, word, grammar and text" (p.51).Apparently, grammar is one of the aspects involved in all types of language skills ranging from listening to writing and is always thought the most difficult by Thai learners.Therefore, writing tasks do not seem easy for them because most of the Thai language systems are different from the English systems.Errors, consequently, can be made at all times.Thep-Ackrapong also states that errors caused by the dominant of the first language are called "the negative interference of the mother tongue" (p.53).
Additionally, Jenwitheesuk (2009) studied the syntactic errors demonstrated in Thai college students' writing and concluded that the causes that led to the errors in EFL learners' paragraphs were mainly from the interference of the first language.She explained, "this is because the learners applied the structures of their mother tongue when they write in English.The differences in both vocabulary and the structures of the two languages cause the problems in writing the second language" (p.986).Similarly, Weijen et al. (2009) examined the use of L1 in writing augmentative essays of 20 second language students.The participants were asked to write under the conditions of think-aloud protocol.The students' writing process as well as their language use was then observed and recorded.The results revealed that all the participants were dominated by L1 while performing the tasks; that is, because of L1 influences, the quality of L2 writing was significantly decreased.It was, therefore, concluded that L1 use during L2 writing had negative impact on L2 students' writing quality and proficiency in terms of writing performance and language structures.In consistence with Jenwitheesuk and Weijen et al., Mojica (2010) explored the writing problems reported by L2 learners from Korea, Turkey, The Philippines, Thailand and China.The results revealed that the two problems that concerned L2 writers the most were grammar and vocabulary.
All in all, grammar and vocabulary are perceived to be the principal problems obstructing the effective writing of ESL/EFL learners.What causes such trouble can be from the different systems between mother tongue and the target language.Due to this, L2 writers are dominated by the rules of their first language, which, eventually, leads to committing errors in their written works.Many researchers have thus conducted studies on problems found in students' writing.Anyhow, most of them have regarded the interference of the mother tongue as the crucial factor that should not be ignored.

L1 Interference as a Cause of L2 Writing Errors
As mentioned earlier, L1 interference occurs when L2 learners transfer their own syntactic knowledge into the use of the target language.Dulay et al. (1982) discuss automatic transfer when students make use of their L1 structures in the target language habitually.Why do students transfer L1 structures when writing in L2 language?Bhela (1999) describes this as the case resulting from the learner's assumption of language equivalence.However, no language is identical regarding structures, lexicons, and systems; hence, the students' prediction of equivalence leads to the cause of error and mistake production in their second language written outcomes.Furthermore, Hashim (1999) defines the term L1 interference as a cross-linguistic and language transfer, which is referred to the interference of the students' mother tongue when they perform their language competence and performance either in spoken or written forms.Here, it means that L1 interference has, over the past few decades, become a major problem of those who learn a new language, and it tends to happen in the productive skills like speaking and writing.Jie (2008) also supportively explains that the influence of the mother tongue affects L2 learning as "language is taken as a set of habits and learning as the establishment of new habits, a view sprung from behaviorism, under which language is essentially a system of habits" (p.36).
Not only do foreign researchers pay much attention to L1 interference in L2 students' writing, but many Thai researchers also do.Tuaychareon (2003) sees that Thai students commit errors and mistakes in syntactic level because of the limited linguistic knowledge.That is, due to inadequate language knowledge, L2 writers make use of their mother tongue in L2 writing; therefore, the use of inappropriate structures and words are always seen.Consistently, Thep-Ackrarapong (2005) states the interference of L1 lexicons is perceived as a main problem in the translation of the target language as well as in writing a second language.The interference, in her sense, is the students' violation of the collocation restrictions such as the words 'do' and 'make ', 'turn on' and 'open', etc.It can be said that the Thai learners tend to violate the collocation rules in using words due to the limited vocabulary, which also further causes the interference to other levels like syntactic and discourse levels.Bennui (2008) defines L1 interference in Thai students' writing as a process in which Thai learners always think in Thai before writing in English.In doing this, errors can exactly be expected as he clarifies, "Students' Thai language structures and culture inevitably interfere with their written English" (p.73).In a nutshell, L1 interference, as defined and explained, is in relation to L2 writers' prediction in terms of syntactic equivalence between first and second language, which leads to such grammatical and lexical errors in L2 writing.

Writing Errors VS Writing Mistakes
When talking about L1 interference, we understand that it is related to mistakes and errors made by L2 writers.Thus, it is necessary to clarify these two terms.Brown (1994, as cited in Petter, 2000) describes mistakes as an unsuccessful use of grammatical rules; that is, learners study the language structures comprehensibly but fail when using them.This failure is perceived as a mistake, while errors refer to "a noticeable deviation from the adult grammar of a native speaker, reflecting the interlanguage competence of the learner" (p. 6).It is reasonable to say that in language learning, an error is what learners make in their L2 writing because they do not know the syntactic as well as lexical structures, whereas a mistake is in relation to the learners' low competence in using a foreign language.Ellis (1997) explains the errors reflect the gaps in the learner's knowledge; that is, an error is produced due to the fact that the learners cannot identify what is correct and incorrect.In contrast, a mistake reflects the learners' inefficient performance; that is, it occurs because the learners are not able to perform what they already know correctly.Jie (2008) also notes, "a mistake occurs as the result of processing limitations rather than lack of competence while an error is the breaches of rules of code" (p.37).According to Jie, an error happens from a lack of requisite knowledge of a language learner.As such, he/she makes such errors in his/her writing because he/she does not know grammatical properties in a new language.The rules of L1 knowledge are then employed in the use of L2 writing, which causes the mother tongue interference.

L1 Interference Categories Found in L2 Writing
In order to assist student writers to enhance their writing performance, such problems should be identified.Hence, an amount of research has, over the past few decades, focused on L1 interference that causes errors in L2 writing.Since each language is not similar in terms of linguistic properties, categories of the interference of the mother tongue are, therefore, varied.Bhela (1999) explored errors in L2 student writers.The participants from four different contexts, including Cambodian, Italian, Spanish and Vietnamese, were assigned to write stories according to the pictures given.Then the L1 interference types found in each written story were classified.The errors caused by the mother tongue were as follows: 1) Apostrophe, 2) Punctuation, 3) Spelling, 4) Prepositions, 5) Capital letters, 6) Present & past continuous tenses, 7) Subject pronouns, 8) vocabulary, and 9) Passive & active voice.Chan (2004) studied the errors in Hong Kong Chinese student writers' writing to examine how syntactic transfer affected the effectiveness of students' writing performance.According to the study results, five syntactic structures were found: 1.The copula: This type of error is involved in the use of verb 'be' as a linking verb in English.Normally, Chinese structures are equivalent to English linguistic features in terms of the use of verb be to link between a subject and a subject complement, which is a noun.However, when a subject with a complement, which is an adjective, is written in Chinese, the verb be is not necessary in a sentence as it can be omitted.
2. Placement of adverbs: Chinese writers encounter this error type because in the Chinese language, adverbs are always placed before verbs.On the other hand, in English, adverbs can occur either before or after verbs.
3. Expressing the existential or presentative function: Similar to the Thai language systems, a Chinese sentence sometimes does not need a subject.As a result, many Chinese students have problems with the use of "There be" structure.

Relative clauses:
This difference between English and Chinese is obvious since in English a relative clause is always placed after a noun as a modifier; in contrast, at times, Chinese relative clause is put before a noun it modifies.
5. Verb transitivity: It is related to the differences of verbs between Chinese and English.For example, some Chinese verbs, which are intransitive, may be transitive in English.
Thep-Ackrapong (2005) points out that grammar is perceived to be the most difficult aspect of learning English from the Thai students' points of view.She divides the influence of the mother tongue into six main categories: 1) Subject-verb agreement, 2) Topic-comment structure, 3) Passive voice, 4) Relative clause, 5) Participial phrase, and 6) Subordination.She urges that these six discrepancies are often made by Thai students not only in writing but also in translating the target texts.Bennui (2008) pursued his research on L1 interference found in Thai university students' paragraphs.He employed the theories of Contrastive Analysis and Error Analysis to identify L1 interference types.According to the study results, he classified L1 interference into three main categories: 1. L1 lexical interference: This sort of interference happens because of the lack of lexical competence.Furthermore, the vocabulary levels of the two languages are different; therefore, when writing or translating in English, Thai students normally use a form of direct translation, which leads to the errors in terms of word choice.The sub-categories of L1 lexical interference are 1) Literal translation of vocabulary use, and 2) The use of Thai words 2. L1 syntactic interference: This category is related to grammatical errors found in students' writing.He divides this interference into seven sub-categories as follows: 1) Word order of Thai structure, 2) Subject-verb agreement, 3) Tense,4) The infinitive, 5) The verb 'have', 6) Prepositions, and 7) Noun determiners.

L1 discourse interference:
This happens because of the differences between the styles of Thai and English text formats, including essay patterns, organization, and concepts.For example, in English, it is essential to include a topic sentence in every paragraph, while a Thai paragraph need not have it.The sub-categories of this interference are 1) Language style level, and 2) Level of cultural knowledge.
In conclusion, it is fair to say that L1 interference in L2 writing has recently been rigorously investigated in both foreign and Thai contexts, and a number of L1 interference categories have been found and proposed in the area of teaching L2 writing.To consider the categories of L1 interference as illustrated above, those that affect L2 writing accuracy need to be determined, since L1 interference has been considered to be the main problem of L2 students' writing difficulty.

Subjects of the Study
The selected subjects were 40 second year English major students, registered for a writing course called Writing Strategies in English at the Faculty of Humanities and Social Sciences, Thepsatri Rajabhat University, Thailand.All of the students had already taken and passed two grammar courses, English Structure in Use, and English Structure in Context.

Error Analysis (EA) for L1 Interference Identification
To study L1 interference in the second language acquisition, either Contrastive Analysis (CA) or Error Analysis (EA) is employed by language researchers.To begin with, the two languages, the mother tongue and the target language, are compared so as to find out what factors influencing second language acquisition are.Basically, the comparison can normally be done with the productive skills like speaking and writing.Richards and Schmidt (2002) explain that Contrastive Analysis (CA) can be used to identify learning problems in a second language, mainly caused by the interference of the first language.In addition, such difficulties detected can lead to the effective production of teaching materials, used to decrease the L1 interference in L2 writing performance.
Even though Contrastive Analysis can be used to analyze L1 interference in L2 language production, it is rather time-consuming as students are asked to write assigned tasks in two languages.Consequently, the theory of Error Analysis (EA), also called Interlanguage Analysis, has been developed.Maicusi et al. (2000) state, "The error analysis is supplanted Contrastive Analysis and became a recognized part of Applied Linguistics" (p.170).James (2001) describes EA as the alternative approach used to investigate the errors in the target language, which are ignored by L2 students.In addition, this ignorance is occasionally from the misuse of the linguistic properties that the users do not know how to deal with it.Jie (2008) endorses Error Analysis, which has been prominently selected to analyze the errors caused by the influence of the mother tongue.Clearly seen, EA does not only assist researchers to identify L1 interference in the target language but also helps L2 learners understand why they make such errors and start learning to correct them.For this reason, Error Analysis is employed in the study in order to detect L1 interference in Thai students' writing so as to come up with error categories of the three aforementioned genres.

Procedure of Data Collection
The participants were assigned to write three paragraphs in three genres, namely narration, description, and comparison/contrast, of at least 150 words each.The selection of genres was based on the course syllabus of Writing Strategies in English.Typically, these genres are required for Thai student writers studying paragraph writing.The three topics were (1) My Memorable Trip, (2) My Ideal House, and (3) Watching News on Television VS Reading News from a Paper.One hour each day was allotted for each paragraph, and an English-English dictionary was allowed.Writing errors caused by L1 interference from the 120 paragraphs were analyzed using Error Analysis (EA).To clearly portrait, the data collection procedure was presented in Figure 1.

Data Analysis
The collected paragraphs were analyzed line by line in order to detect errors for L1 interference categorization, using Error Analysis (EA), and all the L1 interference categories obtained from the analysis were then verified by three language experts, having been teaching writing courses to Thai university students for at least 10 years, so as to come up with appropriate error types, which were seen as genuine writing problems of Thai EFL students.The descriptive statistics used in this study were frequency, mean scores, and percentage.

Results
According to the analysis of 120 pieces of writing in the three genres, 16 L1 interference categories were found.These were verb tense, word choice, sentence structure, article, preposition, modal/auxiliary, singular/plural form, fragment, verb form, pronoun, run-on sentence, infinitive/gerund, transition, subject-verb agreement, parallel structure, and comparison structure.Although all the three genres shared the same characteristics in terms of error categories, obviously, there was a difference in the frequency of errors made as claimed.The analyzed data of each writing genre are presented in Tables 1-3 below.

Table 2. Errors Caused by L1 Interference Found in Descriptive Writing
As shown in Table 2, unlike narrative writing, verb tense was not perceived as the most frequent error in descriptive writing since the students rarely made errors in terms of tenses.However, the three most frequent errors were article (20.90 %), sentence structure (13.65%), and word choice (12.58%), relatively similar to narrative writing.Interestingly, singular/plural form (10.59%), and subject-verb agreement (8.17%) also became students' problems when writing descriptive paragraphs.Because of the writing topic assigned "My Ideal House", the student writers had to describe what their ideal houses were like by using a lot of nouns and simple As can clearly be seen from the data in Table 3, a genre significantly affects error types.In narrative and descriptive writing, comparison was the least frequent error the students made in their written work.On the other hand, when they were assigned to write a comparison/contrast paragraph, some errors regarding comparison structure were constantly made as they needed to use comparative patterns to express their thoughts.Not surprisingly, singular/plural form (16.95%), word choice (13.23%), article (13.16%), subject-verb agreement (12.09%), and sentence structure (9.37%) were still the five most frequent errors, somewhat similar to narrative and descriptive writing.The other common error types found in comparison/contrast writing were preposition (7.51%), infinitive/gerund (6.94%), modal/auxiliary (4.86%), run-on sentence (3.36%), comparison structure (3.29%), verb form (2%), transition (1.79%), parallel structure (1.65%), pronoun (1.50%), fragment (1.29%), and verb tense (1%), respectively.
In sum, it is reasonable to say that although there is considerable overlap in the common errors caused by L1 interference, the number of errors of specific categories varied, depending on a particular genre.In order to provide good feedback for students' writing, error categories of each text type should be taken into consideration.

Discussion
As stated earlier, a good revision is needed during the writing process in order to make a paragraph or an essay more accurate.The knowledge regarding the differences between L1 and L2 linguistic properties is thus perceived as essential.Ferris ( 2004), a well-known researcher in the area of error feedback in L2 writing, states that prior to giving feedback to students, it is crucial for a writing teacher to be aware of error categories frequently found in his/her students' writing.For this reason, over the last few decades, many language researchers have paid attention to writing error detection, resulting from the interference of the first language.Maros et al. (2007) investigated grammatical errors made by Malaysian students.The findings showed that their errors caused by L1 interference were the use of articles, subject-verb agreement, and copula 'be'.As can be seen, both Malaysian and Thai students had similar L1 interference categories, which were the use of articles and subject-verb agreement.According to the results of this study, it can be seen that each writing genre had different numbers of error frequency, which could be used to strongly claim that when teaching writing, a genre also had an impact on L1 error categories.To clearly explain, a comparison of error types found in three genres is shown in Figure 2.

Figure 2. Comparison of Error Types Found in Three Genres
In general, not only does a writing teacher provide feedback according to the errors he/she has seen in students' written work, but also a grammar lesson based on the errors found can be more effectively prepared in accordance with a writing genre being taught.As seen in Figure 2, the L1 error categories of narrative, descriptive, and comparison/contrast writing genres are compared and presented.This indicates that, in narrative writing, an intensive focus of errors should be on verb tense, while subject-verb agreement should be the focus of descriptive and comparison/contrast writing.Overall, among these three genres, word choice, sentence structure, preposition, verb form, run-on sentence, modal/auxiliary, and transition are seen to occur comparatively equally.In description, the uses of article and word choice become the first two error types that should be taught to L2 student writers.It may be because of the topic assigned to the participants to write as they were required to use a lot of nouns and adjectives in order to describe their ideal houses.Since the Thai language has few or no articles or determiners in front of nouns, this error category emerges as a frequent writing problem for Thai students.In terms of comparison/contrast writing, comparison structure errors arise the most, compared to the other two genres.Therefore, it is necessary to emphasize this structural feature when teaching L2 students to write comparison/contrast paragraphs.

Conclusion
Although writing has been considered as the most difficult of the four English skills as mentioned in Introduction, it is feasible for L2 student writers to enhance their writing accuracy.As a rule, compared to a medical service, prior to coming up with an appropriate remedy, a disease should be first diagnosed its characteristics of symptoms.Similar to the nature of this study, before a good piece of writing with as few errors as possible is produced, the causes of ineffective writing should also be identified.Since grammatical features of each language are not similar, errors made are obviously different.Hyland and Anan (2006) state that the awareness of syntactic differences of the two languages is indispensible for both teachers and students who need to produce a perfect piece of writing with accurate grammatical structures.It is, therefore, fair to say that the results of this study can be beneficial to the teaching of English writing in the Thai context as writing teachers as well as Thai EFL students will be aware of what types of errors should be emphasized when practicing writing English paragraphs in different text types.However, in order to make this area of research more applicable, further studies regarding correlations of L1 interference to L2 writing in various genres and with different topics could be conducted.

Figure 1 .
Figure 1.Procedure of Data Collection

Table 3 .
Errors Caused by L1 Interference Found in Comparison/Contrast Writing found in the study of Abushihub et al., which were verb tense, preposition, article, word choice, and verb form.In order to reduce errors caused by L1 interference,Maros et al. and Abushihub et al. suggestedthe development of teaching pedagogies, textbooks, and syllabus designs be taken into consideration.Nonetheless, prior to taking teaching materials and approaches into account, L1 interference categories in each text type should be considered as the first step of the development of teaching aids and course syllabi.That is, a writing teacher has to prioritize what kinds of errors, especially in each different genre, should be initially focused on, which a great deal of research, conducted in Thailand as well as in EFL/ESL contexts, failed to mention.