This study aims to investigate the impact of topic familiarity and vocabulary learning tasks on vocabulary acquisition in an ESP (English for Specific Purposes) setting, focusing on 16 adult learners with varying proficiency levels (A1-B1), all training to be cooks. Participants worked with six cooking recipes, three on familiar topics and three on unfamiliar topics, with 30 target words assigned to one of three tasks: word list, flashcards, or fill-in-the-gaps. Immediate and delayed post-tests (three weeks later) were administered using the Vocabulary Knowledge Scale (VKS). Despite the small sample size, significant differences in retention are noted across proficiency levels and task types over time. Results from repeated-measures ANOVAs showed that topic familiarity alone did not significantly impact vocabulary acquisition. However, the interaction between topic familiarity and task type was significant, as were the effects of task types and proficiency levels individually. The interaction between task type and proficiency level also showed a significant effect on vocabulary learning. Participants generally performed better with the fill-in-the-gaps method, but these effects decreased over time. The study highlights the importance of considering both proficiency levels and task types for effective vocabulary instruction.

The current study aims to examine whether topic familiarity can be associated with, and can also substantially contribute to, the testlet effect often found among items sharing a common passage in reading comprehension tests, particularly by using the Multidimensional Item Response Theory (MIRT) bifactor model as the main data analytic scheme. Data analyzed in this study were item scores collected from 830 Korean high school students who took a 8-passage, 32-item reading comprehension test (4 items per passage) and a 40-item self-reported topic familiarity questionnaire (5 items per passage). The results of analysis revealed that (a) the bifactor model best fit the test data; (b) the self-reported topic familiarity score was not correlated with the testlet factor scores at a statistically significant level; and (c) the overall topic familiarity score had a positive correlation with the general reading ability score, however. Implications of these major findings are discussed in terms of the usefulness of the bifactor model and the nature of testlet effects in reading tests, along with avenues for further investigation.