PROJECT SUMMARY/ABSTRACT Most children amass a complex lexicon effortlessly from the language they hear, but word-learning is very challenging for children with language impairment. Cross-situational statistical word-learning (CSWL) - the ability to learn words by tracking co-occurrence statistics of words and their referents over time, is a fundamental mechanism underlying lexical acquisition. Outside the laboratory, children with DLD and their typically developing (TD) peers learn words from language input that is replete with variability. Yet, research examining CSWL has not considered how variability in perceptual properties of objects (e.g., big cup, blue cup) and input from multiple speakers (e.g., both mom and dad saying “cup”) impact children’s ability to learn word-to-referent mappings. In the current proposal, a total of 60 school-aged children will participate in a study addressing the following Specific Aims: 1.) Examine the separate and combined effects of speaker and exemplar variability on cross- situational word-learning 2.) Determine the extent to which weaknesses in lexical and/or semantic knowledge influence word-learning performance under different variability conditions. An eye-tracking visual world paradigm will be used to examine word-learning performance via a cross-situational word-learning (CSWL) paradigm in three groups of children: English-speaking monolingual typically developing (TD) children, children with developmental language disorder (DLD), and TD bilingual children. Performance in DLD relative to TD will be examined to investigate mechanisms that underlie language weaknesses in DLD and the skills that are crucial to CSWL. TD Spanish-English bilingual children resemble monolingual DLD children in their language-specific lexical skills due to distributed exposure but resemble monolingual TD children in their semantic skills when their vocabulary knowledge is aggregated across both languages. Therefore, performance in TD bilingual children relative to TD monolingual children will be examined to investigate whether language-specific lexical skills or conceptual vocabulary knowledge is more important for CSWL. Together, the findings will inform current models of lexical acquisition, which rarely account for learning in diverse and atypical populations or for variability in the input and will also provide new theoretical insights into how input characteristics and individual differences in language ability interact. Results from the current proposal have the long-term potential to inform treatment and educational strategies targeting word-learning for children with DLD. During the training period, the applicant will gain experience in developing and conducting rigorous scientific experiments in children with DLD; acquire new knowledge in lexical-semantic development and categorization, advanced analytical techniques, and eye- tracking methodology, professional issues, responsible conduct of research, and open scienc...