This study has investigated L2 learners' task motivation with a total of 212 Korean high school students from the perspective of self-determination theory. Three separate studies were created, each focusing on the relationship between one of the three basic psychological needs recognized in self-determination theory—autonomy, competence, and relatedness—and L2 learners' task motivation. In each study, the participants engaged in an oral argumentative task which asked them to negotiate and discuss with their task partner in order to reach agreement, while other characteristics of the task were varied.

The results across the three studies demonstrated that L2 learners who had similar or equal levels of general motivation toward English learning (trait motivation) presented fairly different levels of task motivation, intention to persist, and task engagement, depending on different task conditions they were placed in, clearly showing that L2 learners' motivation is not stable throughout the learning process. It was also discovered that only the most self-determined subtypes of general motivation toward English learning (e.g., identified regulation and intrinsic motivation) were consistently related to task motivation. In addition, correlation results suggest that it is the participants' task motivation, rather than their trait motivation, that is generally more closely related with task engagement, task performance quality, and intention to persist in doing the given task.

The findings of this study indicate that L2 learners' task motivation is multifaceted and L2 learners can behave differently depending on different task conditions, even though they have the same level of general motivation toward English learning. This leads to a pedagogical implication that classroom teachers can benefit from collecting, analyzing, and interpreting classroom data about learners' feelings and opinions toward learning tasks to discover which task features make their own learners more or less engaged in certain tasks and eventually create tasks that can enhance their learners' motivation. This research also provides compelling reasons for further research into the complex relationships between tasks and L2 motivation.