Abstract
This research examined both the short-term and long-term effects of processing instruction (PI) and its main element, structured input (SI), on learners’ acquisition of English passive forms. A total of 70 English as a second language (ESL) learners participated in the study and were randomly divided into three groups: a PI group (
n
= 24), an SI group (
n
= 25), and a control group (
n
= 21). Participants in the PI and SI groups completed 1 hr of computer-based instructional activities, whereas the control group received no instructional treatment. Learners’ performance was evaluated using self-paced reading (SPR) and self-paced listening (SPL) tasks, which assessed response accuracy, picture selection response time, and reading or listening time at three points: before instruction, immediately after instruction, and after a delay. Findings showed that both the PI and SI groups achieved significant gains in accuracy on the SPR and SPL tasks at the immediate and delayed post-tests, while no improvement was observed in the control group. However, none of the groups demonstrated significant improvement in response time or reading time on the SPR task. In contrast, results from the SPL task indicated that the PI group showed significant reductions in both response time and listening time at both post-tests, whereas the SI group showed improvement in response time only at the immediate post-test. Despite these differences, no statistically significant differences were found between the PI and SI groups overall.