Previous studies on SLA have shed light on the connection between input, interaction and interlanguage development. The study done by Hatch and Wagner-Gough (1976) argued that learners’ participation in conversation gives learners a forum to practice and helps develop L2 syntax. Sato (1986) claimed that conversational interaction is critical for learning in that it serves as a source for linguistically salient features to develop. This case study therefore examines the development of English ability of two adult NNS subjects during a five month period in which conversational interaction was carried out. The research questions are formulated as the following:

(1)How does the learners’ use of each grammar form develop through the course of the treatment?
1.1How does the use of nouns by the subject who went through information gap activities with nouns develop in obligatory singular and plural contexts? What are the differences regarding the two contexts?
1.2How does the use of verbs by the subject who went through information gap activities with verbs develop in obligatory nonpast and past contexts? What are the differences regarding the two contexts?
1.3How does the presence of quantifiers affect the subject’s performance on noun markings through the sessions?
1.4How does the presence of temporal adverbials affect the subject’s performance on verb forms through the sessions?
(2)Do the learners improve their use of the specific grammar structure as measured by the comparison from pretest to posttest?
2.1Does the subject who went through information gap activities with nouns improve the use of noun markings? Are the improvements in obligatory singular contexts, plural contexts, or both? Do the effects differ for regular and irregular nouns?
2.2Does the subject who went through information gap activities with verbs improve the use of verb forms? Are the improvements in obligatory nonpast contexts, past contexts, or both? Do the effects differ for regular and irregular verbs?
(3)Are improvements observed on the posttest sustained 5 weeks later?

All the data with respect to interaction from the treatments and tests were transcribed to examine learners’ language development process. The result shows the subjects’ progress, especially for regular nouns and verbs in the posttest and delayed posttest. Qualitative analysis and discussion were made accordingly. Teaching implications are drawn at the last part.

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