Grounded in the biopsychosocial models of expressive language in autism spectrum disorder (ASD) and fragile X syndrome (FXS), this dissertation included two novel studies that examined the role of biological (i.e., physiology), psychological (i.e., autistic traits, anxiety symptoms, and child affect) and social (i.e., communication partner…

Generalization is the ability to apply regularities to novel instances, for example, correctly guessing that the plural for the novel English word 'wug' should be 'wugs'. Early language learners make overgeneralization errors like 'mouses', applying regularities beyond their attested uses. Theories concerned with the question of how learners learn…

In English as a lingua franca (ELF) communication, in which English is used as a common language among interlocutors of different first languages, successful communication often features communication strategies that enhance mutual understanding and relationship management. Although prior research suggests that including such strategies in English…

This thesis examines whether native, heritage, and L2 speakers of Spanish engage a morphological layer of representation in the processing of inflected words, and whether they do so with both regularly- and irregularly-inflected words. Also examined is whether this tendency towards compositional (i.e. morphological rule-based) processing is…

The purpose of this study was to explore whether students with Autism Spectrum Disorders (ASD) could develop enhanced expressive speech acquisition through intervention via "Precision Songs" (Kantz & Kantz, 2004) and an eclectic curricula versus using only an eclectic curricula. Three hypotheses guided the study: (1) there is no…

Children who enter kindergarten with low oral language skills are at great risk for reading problems, especially in the areas of vocabulary and comprehension. The purpose of this study was to evaluate the effectiveness of two instructional vocabulary methods of storybook reading with children who exhibit typically developing language skills and…

This study investigated the effects of shared reading on oral vocabulary development with 42 second language (L2) learners in Dakar, Senegal. Participants, ranging from four to six years old, were taught French target words using predictable books, non-predicable books, and control activities of the typical local instructional practice of using…

The purposes of this study were to determine the effectiveness of a vocabulary intervention for first-grade students at risk for reading and language difficulties and to compare the results of a regression discontinuity design to those of an experimental design. The specific research questions were: (1) Do first-graders who are at risk of reading…

Theories of language acquisition have highlighted the importance of adult speakers as active participants in children's language learning. However, in many communities children are reported to be rarely directly engaged by their caregivers. This raises the possibility that children in these communities learn language from observing 3 rd party…