The present experimental study explores developmental characteristics of Korean EFL learners’ English negatives and yes-no interrogatives. Adopting the functional category acquisition framework within the UG theory, this study investigated 12 elementary and secondary school students’ interlanguage grammar by elicited production. The results showed that the learners’ interlanguage grammar developed gradually from VP to IP and CP structures in English negatives. However, their interlanguage grammar did not show gradual developmental tendency in yes-no interrogatives. The acquisition rate of negatives generally increased with the learners’ level whereas there existed individual variation in the acquisition rate and developmental aspect of yes-no interrogatives. This result suggests that CP structures instantiated by yes-no interrogatives seem to be acquired from the initial stage by some learners.

This study deals with Korean learners' acquisition of English negatives. According to previous research, learners of English pass through a stage that demonstrates the characteristics of learners' interlanguage. Using a learner corpus (KELC), we show that Korean learners progress through several developmental stages before they master English negation. In addition, the errors made at each developmental stage reflect learners' knowledge of syntactic representation in terms of functional categories. Specifically, at the beginner level, the learners do not use auxiliaries at all. As they move to the intermediate level at which the functional category begins to be used, they start using auxiliaries in front of the negator. However, their outcomes are undermined with inflection errors either on the auxiliary or on the thematic verb. Finally, at the advanced level, the inflection errors disappear although still the present tense dominates where the past tense is required. This developmental pattern is in accord with the stages reported in the literature and the maturation of syntactic representation (i.e., functional categories).