In this preregistered, longitudinal study of early code-switching, 34 US-born, Spanish–English bilingual children were recorded with a bilingual family member at 2;6 and 3;6, in Spanish-designated and English-designated interactions. Children’s Spanish and English expressive vocabulary and their exposure to code-switching were measured through direct assessment and caregiver report. The children code-switched most frequently at speaker changes; within-turn and within-utterance codeswitching were rare. By 3;6, switches to English were significantly more frequent than switches to Spanish. At both ages, Spanish proficiency was a negative predictor of the frequency of switching to English, but children’s degree of English dominance uniquely explained additional variance. Thus, children appear to code-switch not merely to fill gaps in their weaker language but to maximize their expressive power. Neither individual differences in exposure to code-switching nor in the interlocutors’ language proficiency were consistently related to the children’s rate of code-switching.

在这项关于早期语码转换的预注册纵向研究中，记录了 34 名美国出生的西班牙语-英语双语儿童在 2;6 和 3;6 时与双语家庭成员进行西班牙语指定和英语指定的互动。儿童的西班牙语和英语表达词汇以及他们对语码转换的接触是通过直接评估和看护者报告来衡量的。孩子们在说话者改变时语码转换最频繁；轮内和话语内语码转换很少见。到 3;6，切换到英语的频率明显高于切换到西班牙语的频率。在这两个年龄段，西班牙语熟练程度是转换为英语频率的负预测因素，但儿童的英语主导程度唯一地解释了额外的差异。因此，孩子们进行语码转换似乎不仅是为了填补他们较弱语言的空白，而且是为了最大限度地发挥他们的表达能力。无论是接触语码转换还是对话者的语言熟练程度的个体差异都与儿童的语码转换率始终相关。