PROJECT SUMMARY/ABSTRACT Word-learning difficulties are common among young autistic children. If unaddressed, these early challenges can negatively affect children’s communicative and academic success. To determine appropriate strategies for early intervention, it is essential to first understand the mechanisms underlying word learning in this highly heterogenous population. Based on previous work, one mechanism available to older autistic children is cross-situational learning (CSL). However, the higher prevalence of word-learning difficulties in ASD suggests the possibility of remaining unknown factors limiting children’s ability to make efficient use of CSL in real-world language environments. One possibility is that autistic children demonstrate delays in early development of CSL with cascading consequences for word learning. Previous findings indicate that older autistic children can use CSL to learn words, but this mechanism has not yet been examined in preschool-age autistic children. Employing a Looking-While-Listening eye-tracking paradigm, Specific Aim 1 (Study 1) of the proposed project will investigate CSL in a younger group of children (2- to 4-years old). A second possibility is that prior CSL studies have not reflected the challenges of children’s natural language environments. Previous studies required children to associate only one exemplar image with each label, whereas in real-world learning situations children encounter many different objects that are all given the same label. To support word learning in these contexts, neurotypical (NT) children tend to categorize objects based on shape (known as the shape bias). Preschool- and school-age autistic children do not share this tendency with NT peers. Without a shape bias, we might expect autistic children to experience word learning difficulties when multiple exemplars are presented matching the same label and shape but varying across other perceptual features (i.e., color). Specific Aim 2 (Study 2) will examine the impact of exemplar variability on novel words in the context of CSL and ostensive training tasks in young autistic children and language-matched NT peers. Finally, Specific Aim 3 (Study 3) will examine child characteristics associated with CSL task performance in ASD. By examining autistic preschool children’s ability to learn words via CSL at a younger age and across variable exemplars, the proposed project will elucidate potential points of vulnerability in word learning for this population. Study findings will advance the NIDCD strategic plan by increasing our understanding of language mechanisms in ASD and how they function differently across individual children and environmental contexts, with clinical implications including therapy stimuli selection and establishing CSL principles as a foundation for future interventions. Training Plan. The applicant’s training will focus on acquiring new methodological and conceptual knowledge in language-learning processes, ...