ดูโค้ด

	In second language acquisition research, it is well-attested that production of functional morphology, e.g. tense and agreement, by L2 learners is variable. The present study examined whether variability exists in production of English past tense marking by L1 Thai speakers. It was hypothesized that variable use of English past tense marking would be observed and that the phenomenon can be accounted for by the Failed Functional Features Hypothesis (FFFH) (e.g. Franceschina, 2001; Hawkins and Chan, 1997; Hawkins and Liszka, 2003), but not by the Missing Surface Inflection Hypothesis (MSIH) (e.g., Lardiere, 1998; Prévost and White, 2000; White, 2003). Three tests, namely Grammaticality Judgment Test, Cloze Test, and Story-telling, were administered to 40 L1 Thai learners: 20 intermediate and 20 advanced learners. The results showed that L1 Thai speakers exhibited variability in their production of English past tense marking across the three tests. Additionally, an asymmetric rate of suppliance of past tense marking was observed. It was found that regular verbs were past-marked less frequently than irregular verbs by both proficiency groups. The suppliance rate of English past tense marking by the two L1 Thai proficiency groups was also higher when adverbial phrases of time indicating pastness were present. The low suppliances of past morphemes including both the representation and the production tasks, and the asymmetric phenomena confirmed the two hypotheses, hence, supporting the FFFH but confounding the MSIH.