The effects of augmentative and alternative communication cursor click modality on language complexity and user perceptions
MetadataShow full item record
PURPOSE: Surface electromyography (sEMG) provides an alternative method for individuals with severe motor impairments to use the voluntary contractions of sparred musculature as inputs into an alternative and augmentative communication (AAC) device. Current research suggests that individuals with typical motor control prefer a sEMG-based click mechanism over a dwell-based click mechanism to operate an on-screen cursor. However, there is no existing data on the effects of cursor click modality on language production in AAC users with motor impairments. The goal of this study was to evaluate the communicative abilities of individuals with neuromuscular disorders when using an AAC device with two different cursor click modalities. METHOD: Twelve individuals with neuromuscular disorders produced synthetic language samples via an on-screen keyboard using an sEMG/accelerometer system with two different click modalities: dwell-based clicking and sEMG-based clicking. A third language sample via natural speech was also recorded. Language sample analysis was used to evaluate language complexity at syntactic, semantic, and ideational levels. To analyze syntactic complexity, language samples were examined for clausal density, conjunction usage, phrase expansions (noun phrase, verb phrase, and prepositional phrase), and mean length of utterance. Semantic complexity was analyzed using measures of moving-average type token ratio, abstract noun usage, metacognitive verb usage, and usage of morphologically complex words. Ideational complexity was analyzed in terms of the extent to which the responses conveyed the participant’s ideas. A questionnaire was used to measure the participants’ perceptions of usefulness for each modality. RESULTS: Mean length of utterance was shorter in the dwell-based click modality than in the sEMG-based click and natural speech modalities. In the sEMG-based click modality the majority of sentences were complex sentences, whereas simple sentences made up the majority in the dwell-based click modality. Morphologically complex word usage was used more frequently in the natural speech modality than in the sEMG-based click modality and used most frequently in the dwell-based click modality. There were no modality-specific trends for ideational complexity. Measures from the questionnaire showed that participants ranked natural speech as being more useful than either of the cursor-click modalities, but all three modalities were rated as at least somewhat useful (5 out of 7 on a rating scale of usefulness). CONCLUSION: This study is the first to evaluate the effects of cursor-click modality on the communicative abilities of individuals with neuromuscular disorders. Despite differences in language complexity on some measures, participants were able to use all three modalities to accurately respond to the language prompt with similar ideational scores. These results support both sEMG and dwell as alternative access methods for controlling a cursor-click system for individuals with neuromuscular disorders in future AAC applications.