The Role of Cognates and Language Distance in Simultaneous Bilingual Children's Productive Vocabulary Acquisition

Abstract This study examined the influence of cognate status and language distance on simultaneous bilingual children's vocabulary acquisition. It aimed to tease apart effects of word‐level similarities and language‐level similarities, while also exploring the role of individual‐level variation in age, exposure, and nontarget language proficiency. Children simultaneously acquiring two closely related languages ( n = 203) or two more distant languages ( n = 109) performed extended versions of the LITMUS Cross‐Linguistic Lexical Task (Haman et al., 2015), a productive vocabulary test with words varying in their phonological similarity to their translation equivalents. Children speaking closely related languages obtained higher vocabulary scores than children speaking more distant languages, who showed a stronger positive effect of phonological similarity. The effect of language distance on vocabulary was not solely driven by the presence of (near‐)identical cognates in the test. These findings show that similarities beyond specific test items and/or beyond the phonological level play a role in vocabulary acquisition.