Potential influence of extensive reading on controlled productive vocabulary

This study explored a possible impact of extensive reading (ER) on vocabulary learning. Participants were 62 English majors who entered a private university in Japan in April 2019 and experienced ER for 13 months. They took the Productive Vocabulary Levels Test at the 2,000-word level 3 times: in April, December and May 2020. The outcomes of paired t-tests with Bonferroni correction revealed that participants achieved higher scores on the 2nd test, but their performance deteriorated on the final test. The model yielded by multiple regression analysis was comprised of the number of series participants read books from and the average percentage grade of MReader quizzes they passed, whose contribution to the post test scores was 14.1%. Follow-up tests were run between 12 students who retained or improved their scores on the delayed test and those who did not. It was found that these 12 participants read more constantly during the spring vacation. They also read more books from one graded reader series and books with fewer than 2,000 words, but read fewer 4,000-to-4,999-word-long books from April to December.