Acquisition of tense and aspect in Toki 'when' clauses in Japanese as a second/foreign language

This study examined the acquisition of tense-aspect in toki 'when' clauses in Japanese among adult learners of Japanese as a second or foreign language. The objective of the study was to investigate if native languages (Language Transfer Hypothesis) and/or inherent semantic characteristics of verbs (Aspect Hypothesis) play a role in the selection of the -ru/-ta endings in toki 'when' clauses. The experimental study was conducted with 37 participants in Experiment 1 (with Achievement verbs in the toki clause position) and 34 participants in Experiment 2 (with Accomplishment, Activity and Stative verbs in the toki clause position). The research instrument consisted of a written version of the Truth Value Judgment Task in which the participants were asked to judge whether a sentence written in Japanese matched the content of a story that preceded it.;The experimental results suggest that the Language Transfer Hypothesis seems to be working independently for the Durative verbs (Experiment 2) category, while the Aspect Hypothesis seems to be independently working for the Achievement verbs (Experiment 1) category. That is, both these hypotheses seem to be working partially for the two categories of verbs (Achievements and Duratives).;There were two sets of results obtained that were not predicted by the two hypotheses. The Language Transfer Hypothesis does not predict the good performances of the Chinese and English speakers for the S1 ru toki S2 ta pattern in the Durative category, while the Aspect Hypothesis does not predict the absence of over-use of -ta with Accomplishment verbs in the present study. The first unpredicted result can possibly be explained by offering another hypothesis, that learners are also sensitive to the durative semantic aspect (or lack thereof) of the verbs in question. That is, their choice of the -ru/-ta morpheme in toki clauses is also influenced by the issue of whether the verb in question represents an event that has a certain length of duration or if it occurs momentarily. For verbs that express a duration-like Accomplishment, Stativity or Activity, the learners associate the -ru with the duration of the verb and are able to select the morpheme correctly. As for the second result that deviated from the predictions, that Accomplishment verbs are not showing errors with over-use of -ta, it can be conjectured that learners are not focusing on the end-point of the Accomplishment verbs, and are treating them as Activity verbs with a finite duration.;Thus, from this study it seems that besides telicity, another semantic feature, namely, the durative versus instantaneous character of the verb is also playing an important role in the choice of the -ru/-ta morphemes in toki clauses. These results have important pedagogical implications in that it may be useful to introduce the inherent semantic characteristics of the verbs such as durativity, telicity and punctuality in the Japanese language classroom and teaching materials. Since the learners seem to be naturally sensitive to these characteristics, introducing them in the classroom will assist them in their internal processing as well as production of the time expressions in Japanese.