1. Ma Rui Tianjin Normal University
A Tentative Study on the Effects of Task Features on L2 Writing Performance: Topic and Genre Effects on Lexical Richness
Ma Rui Tianjin Normal University

2. Motivation for the research
Tasks play a central role in current SLA research and language pedagogy, thus trigger the exploration of their contextualization in language assessment.
Sequencing and generalizing tasks in the scope of language testing have always been problematic. In fact, identification of valid sequencing criteria is ‘one of the oldest unsolved problems’ (Brown 1989: 42).
Task feature analysis is more initial and essential for task sequence potential.
most of the studies focused on speaking rather than writing as productive language skills

3. The role of task features in writing
Task features (or variables) in writing tests are ‘those elements that must be manipulated and controlled to give every test taker the opportunity to produce his or her best performance’ (Hamp-Lyons 1990: 73).
To describe whether and how some of the features affect language performance by manipulating task variables
In standardized writing tests like IELTS , topic variable is the only manipulated feature within the same genre that makes difference between tasks, while different genres might affect writing performance differently

4. Lexical richness
According to Read, there are generally four approaches to measure lexical richness
lexical variation (LV)
lexical sophistication (LS)
lexical density (LD)
number of errors

5. Measures of lexical variation
Type/token ratio (TTR)
Standardised type/token ratio (STTR)

6. Type/token ratio (TTR)

7. Standardised type/token ratio (STTR)
In order to avoid unreliability, a modified method is used—standardised type/token ratio.
STTR is computed in every n words, then a running average is computed, which means that you get an average TTR based on consecutive n-word chunks of text

8. Measures of lexical sophistication
The Lexical Frequency Profile (LFP)
P_Lex

9. P_lex
‘P_Lex is a computer programme to assess lexical difficulty of the texts. It is specially designed to assess the lexical richness of texts’ (P_Lex Instruction: 1).
P_Lex takes word frequency as the basic theory for classification.
‘Difficult’ in this context means any word which is not found in the high frequency list in P_Lex dictionary files.

10. The study Research Questions
Do topics in descriptive writing affect performance in terms of lexical richness?
Do topics in argumentative writing affect performance in terms of lexical richness?
Does genre affect performance in terms of word richness?

11. The study
Subjects
79 L1 Chinese mainland learners who took the four-week EAP course conducted by the Lancaster University Linguistics Department in 2004
Language proficiency: in IELTS

12. The study Data collection
All data involved in this study comes from LANCAWE corpus, which is an ongoing project at the moment.

13. The study Design of the study independent variables: topic & genre
dependent variables: lexical richness
test-retest method was adopted to check the reliability of the research (T2 & T3)

14. The study Methods and procedures 1. Task characteristics analysis
topic variable was elicited as the only difference among the three tests
Topics of tasks in the 3 tests

15. The study Methods and procedures 2. Statistic measurement
oneway ANOVA, paired samples T-test, and correlation analysis have been conducted in the study.

16. Results and findings
For STTR, The results got in T2 were always opposite to the results in T3.

17. Results and findings
There are indications that measure of variation by means of TTR or STTR is unsuitable for proficiency with 3000 words above (Vermeer 2000). The subjects in this study is supposed to be beyond this level, which renders STTR measures less suitable for this study. Vermeer suggested that more effective measures of lexical richness might be based not on the distribution of or the relation between the types and tokens, but on the degree of difficulty of the words used. Inspired by Vermeer’s conclusion, we are more confident of the validity of using P_Lex as a measure of lexical richness.

18. Results and findings
Taking research findings from P_Lex, it seems clear to answer the research questions:
Topic does not significantly affect lexical richness in descriptive writing
There is a significant difference between topics on lexical richness in argumentative writing.
Lexical richness in descriptive writing is clearly distinct from that in argumentative writing. The effect of genre difference is statistically significant.

19. Conclusions
For the insight of these findings in terms of task design, we might tentatively say that in convergent tasks, topic factor does not cause any difference on performance according to lexical richness. However, in divergent tasks, we must be cautious of the selection of different topics as they can elicit difference on performance.

20. Limitations of the study
Future research

21. References
Brown, J. D. (1989) "Criterion-referenced test reliability", University of Hawaii Working Papers in English as a Second Language, 8(1),
Hamp-Lyons, L. (1991) "Basis concepts". In Assessing second language writing in academic contexts(Ed, Hamp-Lyons, L.): Norwood, NJ: Ablex.
Read, J. (2000) Assessing vocabulary: Cambridge: Cambridge University Press.
Vermeer, A. (2000) "Coming to grips with lexical richness in spontaneous speech data", Language Testing, 17(1),