Internal state language (ISL) research contains knowledge gaps, including dimensionality and predictors of growth, addressed here in a two-aim study. Parent-reported expressive language from N = 6,373 monolingual, English-speaking toddlers (Mage = 23.5mos, 46% male, 57% white) was collected using cross-sectional and longitudinal data in WordBank. Exploratory and confirmatory factor analyses suggested a best-fitting one-factor model of ISL. The single-factor model of ISL was then submitted to hierarchical linear modeling to evaluate predictors of ISL development. Age 2 ISL production was predicted by child sex, wherein females outperform males, and maternal education, wherein higher education contributes to higher ISL. Only maternal education emerged as a significant predictor of ISL growth. These results provide support to theory suggesting a unitary construct of ISL, as opposed to considering ISL as categorical, and further illustrate linear growth through the second postnatal year that varies as a function of child sex and maternal education.

内部状态语言（ISL）研究包含知识差距，包括维度和增长预测因素，在此通过双目标研究解决。使用 WordBank 中的横断面和纵向数据收集了N = 6,373 名单语英语幼儿（年龄= 23.5 岁，46% 男性，57% 白人）的家长报告的表达语言。探索性和验证性因素分析提出了 ISL 的最佳拟合单因素模型。然后将 ISL 的单因素模型提交给分层线性模型，以评估 ISL 发展的预测因素。 2 岁 ISL 的产生是通过儿童性别（女性表现优于男性）和母亲教育（其中高等教育有助于提高 ISL）来预测的。只有母亲教育成为 ISL 增长的重要预测因素。这些结果支持了 ISL 单一结构的理论，而不是将 ISL 视为分类的，并进一步说明了出生后第二年的线性增长随儿童性别和母亲教育的变化而变化。