Key word signing (KWS) is a form of augmentative and alternative communication (AAC) frequently used with both children and adults with intellectual disabilities (ID). Communication problems are common in people with ID, and can be caused by their ID and/or by additional disorders. AAC offers different methods to address these communication problems and let people with ID make use of their communicative abilities to the fullest. KWS is one of many AAC systems that can be used (often combined with other systems such as visualisations and speech-generating devices) to support both receptive and expressive communication. It can be used to offer young children a tool for the earliest interactions, to aid in language development, and as a functional, everyday communication means both in children and in adults. The latter group was the focus of this research project. Little is known about these adults and the way they use KWS. Most available literature studied the acquisition of KWS and did not look beyond the therapy room, or only included young children or adolescents. The aim of this research project was to examine the functional KWS use in adults with ID in Flanders, Belgium.A first step was to map the prevalence of KWS use among adults with ID, and to explore the characteristics of these KWS users and their support staff in general. This was done in a survey study, in which all Flemish residential (RP) and day care programs (DP) for adults with ID were contacted by phone. Those programs that indicated use of KWS with one or more of their clients, were asked to fill out a questionnaire. Of the 295 included RP and DP, a few over half used KWS. Programs which did not use KWS, often showed a lack of knowledge regarding KWS. A questionnaire about their KWS use was completed by 93 of the programs. A quarter of their clients actively used KWS. Most adults with ID used 10 to 50 signs, whereas the majority of their support workers used fewer than 10 signs. Sign knowledge and attitude of support staff related significantly to the sign knowledge of their clients. Many service providers reported that their support staff had motivational issues concerning the implementation of KWS. Next, three groups of variables that can be linked to KWS use were studied in this project. A first group of variables are the characteristics of the signs of the KWS system that is used. Therefore, in the second study of this research project, we investigated the influence of the sign characteristics of the Flemish KWS system Spreken Met Ondersteuning van Gebaren (SMOG, Speaking with support of signs) on the functional KWS use of 119 adults with ID. We determined the phonological, iconic, and referential characteristics of the basic SMOG signs. The functional KWS use of the 119 participating adults was evaluated using a questionnaire that was filled out by their support workers. In a generalized linear model with a negative binomial distribution (with loglink), we found that the referential characteristics (semantic category, grammatical class, and referential concreteness) had the strongest influence on sign functionality. The iconicity of the signs also played a part, but phonological characteristics were not significantly related to functional sign use. The characteristics of the KWS users themselves are the next group of variables related to KWS use. We studied a selection of client characteristics, namely cognition and language and communication skills, in the third part of this research project. In a cross-sectional observation study, we related these characteristics, as measured with standardized intelligence, language, and communication tests, of 40 participating KWS users to their functional KWS use. This functional KWS use was evaluated using a specifically developed narrative task, and during a 15-minute conversation between the KWS user and the researcher. Mental age did not relate to the KWS use of our participants. Test results on the language and communication tests only correlated with the verbal measures of the functional KWS use, but not with manual sign measures. Functional KWS use during the narrative task did correlate significantly with KWS use during the conversation, indicating that the narrative task is a valid method for evaluating functional KWS use in adults with ID.In the fourth and final study of this research project, KWS was introduced in a Flemish residential and day care service for adults with ID. This was done using a KWS program, in which we taught KWS to eight KWS ambassadors during four 2- hour workshops. In a sign of the week approach, 100 manual signs and the KWS approach were then gradually introduced to all support workers and clients of the service. We evaluated the functional KWS use of 15 adults with ID and communication problems in a narrative task and during a conversation with their support staff, before and after the intervention. A third group of variables possibly of influence on KWS use (besides sign and client characteristics), namely characteristics of the environment, were also investigated in this intervention study. Therefore, we evaluated the functional KWS use of the support workers before and after the intervention as well, during the conversation with their clients. The KWS use of both clients and support staff had increased significantly after the intervention. Clients used KWS for a variety of communicative functions.The results of this research project revealed four important points of action: 1. KWS should be made more accessible in Flanders. This could be done by using the signs from Vlaamse Gebarentaal (VGT, Flemish Sign Language) with a KWS approach instead of the phonologically adapted SMOG signs. Using signs from VGT would also change the SMOG system into a system with an unrestricted vocabulary, which could benefit KWS users in need of a larger or more specific vocabulary. The application of this altered KWS system in individuals with ID should be further studied.2. Alternative methods for language and communication evaluation than the standard-ones, should be used to evaluate these skills in adults with ID who use KWS in particular and AAC in general. The developed narrative task could be a starting point, that should be examined in more detail.3. No prerequisites should be used for allowing an adult with ID to use KWS. Every adult with ID who can understand and/or produce manual signs, can possibly benefit from using KWS. The functional use of KWS should be studied in a larger group of adults with ID, and in individuals with communication impairments that are caused by other disorders as well. 4. KWS can be introduced in a residence or day care centre for adults with ID using a KWS training program that consists of workshops and a sign of the week approach, combined with sufficient resources (such as photographs and video clips of the manual signs). Individual therapy is not always necessary, and many adults with ID are capable of learning KWS through their support staff. How the attitude and motivational issues of support staff could best be influenced, should be further investigated.Our research project shows that, if these points of action were implemented, this could benefit the implementation and functional use of KWS in adults with ID. The ultimate goal of this study, as of any AAC intervention, is to support adults with ID in attaining communicative competence using their means of AAC, in this case KWS. nrpages: 277 status: published