This study investigated the effects of contextual diversity (CD) on second language incidental vocabulary learning. A total of 124 Japanese learners of English were allocated to a control group or 2 experimental groups, either a high contextual diversity (HCD) or a low contextual diversity (LCD) group. Participants in the HCD group encountered target words across three different texts that varied in genre and topic, while those in the LCD group read three different texts that shared the same genre and topic. Meaning recall and recognition tests were conducted at pretest, immediate posttest, and delayed posttest. Results showed that HCD outperformed LCD on meaning recognition at the delayed posttest. Moreover, learners with greater prior vocabulary knowledge tended to benefit more from contextually varied input, whereas such input may have adverse effects on learners with lower lexical proficiency. This study offers insights into the role of CD in incidental vocabulary acquisition and provides pedagogical implications for optimally incorporating input variability into L2 vocabulary instruction.

The present study examined whether length of bilingual experience and language ability contributed to cross-situational word learning (XSWL) in Spanish-English bilingual school-aged children. We contrasted performance in a high variability condition, where children were exposed to multiple speakers and exemplars simultaneously, to performance in a condition where children were exposed to no variability in either speakers or exemplars. Results revealed graded effects of bilingualism and language ability on XSWL under conditions of increased variability. Specifically, bilingualism bolstered learning when variability was present in the input but not when variability was absent in the input. Similarly, robust language abilities supported learning in the high variability condition. In contrast, children with weaker language skills learned more word-object associations in the no variability condition than in the high variability condition. Together, the results suggest that variation in the learner and variation in the input interact and modulate mechanisms of lexical learning in children.