Age and knowledge of morphosyntax in English as an additional language: Grammatical judgment and error correction

Research on age and second language acquisition (L2A) is vast, but inconclusive. Such research has mainly been motivated by the Critical Period Hypothesis (CPH), which postulates that language acquisition becomes extremely difficult after the onset of puberty. Also, there is a lack of research on age and third/additional language (L3/Ln) learning. To fill this gap, this dissertation examines differences in morphosyntactic knowledge between early and late learners of English as a L3/Ln. In this study, `early' and `late' learners are those participants first exposed to English as a medium of instruction (MOI) in 1st and 11th grades, respectively. Participants' morphosyntactic knowledge was assessed based on two tasks: (a) a Grammaticality Judgment Task (GJT) and (b) an editing task, which required participants to correct morphosyntactic errors. Three hundred and thirty five undergraduate and graduate students from two universities in Pakistan voluntarily participated in the research. Results of the group comparisons showed no statistically significant differences between early and late learners on the GJT; however, on the editing task, a modest but significant difference was observed between the two groups, with late learners scoring higher. This finding contradicts the predictions of the CPH. On individual morphosyntactic features in the GJT, a significant difference was observed between the two groups on past tense and third person singular. The effect sizes supported an edge for late learners. In contrast to the GJT, on the editing task all morphosyntactic features (a total of eight features) except adverb suffix, present progressive, and past tense showed a small but significant difference, again favoring late learners. In terms of task difficulty, both groups attained higher scores on the GJT and lower scores on the editing task. Also, a strong and statistically significant correlation was found between scores for grammatical and ungrammatical stimuli on the GJT, but a very weak and statistically non-significant correlation between the grammatical and ungrammatical halves of the GJT and the editing task. Results showed that early L3/Ln learners did not have an edge over late L3/Ln learners in their morphosyntactic proficiency in this English as an additional language context. This dissertation explored L3/Ln learning by predominantly Urdu and Punjabi bilingual speakers, a previously unexplored population. The two measures used provided complementary perspectives on grammatical knowledge. Future research should also examine early and late proficiency differences using a more ecologically valid measure (e.g., a writing task)