Measuring Aided Language Development - Project Summary/ Abstract For individuals who use picture symbols to communicate (i.e., augmentative and alternative communication/AAC), validated measures to characterize aided language productions currently do not exist. Researchers and clinicians need to have confidence that when they measure a child’s language productions, the measures they use accurately reflect the constructs of interest. Although many measures designed to characterize spoken language development have been developed in recent decades, comparable psychometrically sound language measures have never been systematically developed for aided communication. Valid measures are required for accurate diagnosis, assessment, and progress monitoring. In the absence of such measures, aided language researchers and clinicians resort to adapting spoken language measures, but some of these measures do not accurately characterize the constructs of interest. Currently, this lack of validated measures severely limits research and clinical practice for these “aided communicators.” Therefore, a critical need exists to develop psychometrically sound measures of aided language acquisition. Failing to conduct this research blocks advancement in rigorous AAC research, resulting in continued reliance on psychometrically questionable measures. The long-term goal of this programmatic line of research is to enhance language acquisition outcomes for aided communicators. The focus of the current proposal is to systematically investigate the psychometric properties of a range of aided language measures, which are based on our Graphic Symbol Utterance and Sentence Development Framework. Our central hypotheses are: (1) psychometrically sound measures can be established to capture growth within and across different dimensions of language acquisition, and (2) some elicitation contexts will be better than others at capturing aided language growth. Specific Aim 1 identifies valid measures to characterize aided language progress. Aim 1A uses existing data to document the psychometric properties of a range of aided language measures for preschoolers at the early stages of aided communication acquisition who have received 4 months of aided language intervention. Aim 1B analyzes language progression for high-performing aided communicators who will receive 24 months of intervention; this allows for investigation across all phases of early aided language acquisition. Specific Aim 2 identifies elicitation contexts that demonstrate the most productive aided language use. Achievement of the aims will result in measures that demonstrate strong reliability, differentiate growth for different populations, describe different dimensions of language growth, and are clinically feasible. This work will chart a new horizon of AAC research that contains valid measures to characterize aided language acquisition for preliterate children with profound speech disorders.