Estimates indicate that more than 4.05 million people in the United States have such severe speech disabilities that they require the use of augmentative and alternative communication (AAC). Since the advent of mass market tablet technologies like the iPad, increasing numbers of families and clinicians are reportedly considering AAC options for preschool-age children with complex communication needs. However, even when early access to AAC technologies is available, accompanying access to evidence-based AAC services -- particularly during the critical early language learning years -- often is not. This puts these children at further risk for the poor expressive language outcomes that have been reported in the AAC literature. To address the long-term public health problems associated with children frequently failing to meet their linguistic and communicative potentials, the current investigation seeks to advance the theoretical and empirical bases of language intervention for children using an AAC iPad application. The proposed project is comprised of the following two specific aims: Aim 1 - To evaluate the impact of an aided AAC modeling intervention incorporating contrastive targets and concentrated modeling on the productive use of a range of simple auxiliary `to be' declaratives and yes-no questions by preschoolers with and without receptive language deficits, and Aim 2 - To evaluate participant ability to generalize to productive use of: both closely related and less related untrained linguistic structures. Eighteen five year old children - 9 with receptive language skills within normal limits and 9 with receptive language deficits - will be included in the study. It is predicted that all children will demonstrae acquisition of the targeted rule-based linguistic structures and that they will evidence at least some ability to generalize. An experimentally controlled single-case, multiple-probe across participants design will be used to evaluate outcomes, and a Simulated Modeling Analysis will be used to measure the statistical significance of each participant's progress. Innovations for the proposed study include: (a) furthering the AAC Translation Hypothesis by efficiently teaching children to `map' spoken language onto symbols using an AAC iPad application, (b) adapting instructional techniques which have been validated in the language disorders literature (incorporation of contrastive targets and concentrated modeling), to address documented problems children using AAC often exhibit with word order; and (c) framing the instructional program in a manner targeting categories of rule-based linguistic structures. This investigation will build clinical and research capacity in undergraduate and graduate speech-language pathology students at the University of Central Florida, and the outcomes of this project will have immediate implications for clinical practice while also contributing to the basis of larger-scale funding applications within a sustained line of research aiming to improve language outcomes and long-term results for children with severe speech impairments who use AAC.