Abstract This study investigates how practice conditions—specifically spacing and contextual variation—affect incidental vocabulary learning during second language reading. While repeated encounters with unfamiliar words support lexical acquisition, it remains unclear how the distribution of exposures and consistency of surrounding contexts modulate this process. Ninety-two Catalan/Spanish bilingual learners of English read texts of approximately 900 words containing 20 pseudowords, which served as novel vocabulary items, under two conditions: three readings of the same text or one reading of three different texts. Each target pseudoword appeared six times across the three readings. Repeated reading was either massed (one session) or spaced over three weekly sessions. Eye movements were recorded to assess online processing of target pseudowords. Results showed that spaced and contextually varied conditions elicited more and longer fixations, indicating increased processing demands. These more difficult conditions were not desirable as they did not facilitate recall or recognition of new vocabulary. Instead, immediate vocabulary gains were greater in the massed condition, which was less cognitively demanding during reading, though these gains declined more sharply. The findings suggest that the effectiveness of practice conditions depends on how well they support processing of previously encountered novel words at an optimal level of difficulty.
Serrano et al. (2025) studied this question.