This study examined how bilingualism and speaker variability influence children’s receptive and expressive cross-situational word learning (CSWL) performance. Effects of bilingualism were assessed both categorically (monolingual vs. bilingual) and continuously (length of bilingual experience). Ninety-five children aged 5–9 years completed a CSWL task under single-speaker and multiple-speaker conditions. Receptive performance was comparable between monolingual and bilingual children and was not influenced by speaker variability. However, within the bilingual sample, greater length of bilingual experience predicted stronger receptive learning. Expressive performance revealed a different pattern: monolinguals produced novel words more accurately than bilinguals. Within bilingual children, longer bilingual experience was associated with higher expressive accuracy. Speaker variability did not significantly affect expressive outcomes, nor did its effects interact with the language group or the length of bilingual experience. These findings suggest that children form representations during CSWL that support partial productions of newly learned words, while also indicating that expressive outcomes may be more sensitive to bilingual experience than receptive outcomes. Together, the results underscore the importance of considering both outcome modality and fine-grained measures of language experience when evaluating bilingual influences on novel word learning.

Infant object exploration affords rich opportunities for learning across the first years of life. During object play, infants use different combinations of fingers, different roles for each hand, and will deconstruct object parts—these fine-grained differences comprise the construct manipulation complexity (MC). In this paper, we characterized the development of MC in a longitudinal design. Ninety typically developing infants were assessed for MC at six monthly visits from 9-14 months of age from a battery of eight objects. Guttman analyses found that MC is cumulative, meaning that infants can do the most complex manipulation skill if they are able to also do all the lower ranked manipulation skills. The order from least complex to most complex was: (1) bimanual manipulation, (2) bimanual manipulation with distinct roles for each hand, (3) object deconstruction, and (4) independent digit movement. These results introduce a new framework for describing fine motor skills involved in infant manipulation.