| This research seeks to achieve two goals: (1) to illuminate the developmental course of speaking proficiency in Japanese learners of English and (2) to disclose the influence of elicitation tasks on oral performance. The data, which were excerpted from a large-scale learner spoken corpus, were objectively analyzed in terms of accuracy, fluency and complexity. One of the unique features of the present study is that the speech samples were divided into six proficiency levels (five intermediate levels and one advanced level). The reliability of this detailed classification of proficiency levels based on holistic evaluation is first established. Then, the utterances of learners at various proficiency levels are compared in an effort to identify the chief characteristics of spoken English for each level.;The second goal, the analysis of task influence, involves an investigation of the interaction between proficiency level and task complexity, i.e., how learners of different proficiencies respond differentially to pedagogic tasks depending on the cognitive demands of the tasks. For this purpose, oral performances elicited by a (dynamic) narrative and a (static) picture description task are compared.;The results show that learners first become able to create longer sentences and only then become more fluent. Accuracy improves at a later stage still, and syntactic complexity (i.e., the degree of subordination) evolves progressively from the Intermediate Low to Intermediate High levels. An interaction between task and proficiency level also exists: the more demanding task elicits longer and more syntactically complex sentences from higher level learners but has no effect on lower level learners. The choice of subordinate finite clauses is also influenced by the nature of the task.;This set of investigations further indicates that learners temporarily go through a phase in which they create utterances that seem deviant from the predicted course of development and which defy a particular typological universal. These seem to be strategies utilized by learners to lighten the cognitive load of spontaneous speech when under the stress of second language communicative pressure. The results reported in this dissertation can be expected to have implications for foreign language pedagogy as well as for the testing of speaking proficiency. |
