Project Summary Early language skills like word learning predict later school, social, and behavioral outcomes. While word learning improves dramatically in year 2, so too do other social, cognitive, and linguistic skills, leading to debate about the factors that support word learning, and why it improves. Understanding early word comprehension (which precedes production) holds promise for clinical applications, where timely diagnosis and intervention is critical. The proposed work ties early word comprehension to other improving skills within infants, across year 2. Its overall objective is to establish specific factors that may make older infants better word learners than younger ones, building the evidence base to support children who struggle with this critical facet of language in future work. Aim 1 is to test whether point comprehension is linked to robust word comprehension. Pointing allows child and caretaker to draw each other’s attention to shared context, much as words do. While prior work links pointing and language, none uses a fine-grained developmental lens with high-sensitivity tasks. Exp. 1 tests the hypothesis that point comprehension, i.e. receptive joint attention, precedes and is correlated with robust word comprehension by testing a longitudinal sample of 10-16 mo’s every 2 weeks on both skills. Aim 2 is to establish the strength of the relationship between linguistic skills and robust word comprehension. Advancing theory on whether and how linguistic skills support each other, Exp. 2-4 test 3 cross-sectional samples of 10-16mo’s on word comprehension alongside their ability to recognize how words sound, and their skill at anticipating the words and sounds in utterances as they unfold. Results will establish whether robust word comprehension is correlated with and thus potentially reliant on these linguistic skills. Aim 3 is to disentangle the roles of maturity and exposure by connecting new word learning to familiar word comprehension. Studies testing familiar word knowledge have a built-in confound between exposure and maturation, since older infants have heard more language, with repercussions for word processing. Studies of new word learning rely on overly simplified learning processes. In an innovative 2-week picture book exposure combined with measures of familiar word knowledge in 14, 18, and 22 mo’s, Exp. 5 isolates maturity and exposure to build a more cohesive theory of word comprehension. The proposed work’s unique multi-task multi-age design ensures scientific rigor in providing insight into exactly what improves over year 2, as infants become better word learners. Successfully completed, this work will establish an important foundation for supporting children with language delays and deficits, with particular relevance for ASD, Developmental Language Delay, and hearing loss.

Project Narrative Identifying how infants learn words is crucial for understanding language development in the first years of life, which has downstream effects on other aspects of lifelong success and achievement. Establishing normative baselines for the skills underlying early word learning has immediate and direct applicability to several populations: children with hearing loss, children with an Autism Spectrum Disorder (ASD), and children with Developmental Language Delays, all of whom previous work has demonstrated show delayed or impaired language abilities, on average, relative to typically-developing children. This program of research will be especially informative for tailoring more accurate assessment and support at younger ages for these populations, by uncovering which aspects of infants’ social and linguistic abilities link up with their early word learning, and the roles that experience and maturation play in this process.