This study investigates the effects of three word-focused exercise conditions on vocabulary learning. The exercises were developed based on the involvement load hypothesis. This study also explores how individual differences (e.g. second-language English proficiency level and working memory) affect vocabulary learning outcomes. A total of 180 Chinese students were equally and randomly assigned to 3 exercise conditions (reading comprehension plus marginal glosses, reading plus gap-fill and reading plus sentence writing). The Vocabulary Knowledge Scale was adapted to measure pre- and post-test vocabulary gains. An n-back task was developed to assess learners' working memory capacity. Results showed that the sentence-writing group yielded the best performance in vocabulary learning, followed by the gap-fill group and finally the reading-comprehension group. General linear model results revealed that learners' English proficiency level and working memory significantly predicted their vocabulary gains. This study expands on prior research by exploring learner-related factors in vocabulary learning. Relevant implications are discussed based on the findings.