The language and communication attributes of graphic symbol communication aids - a systematic review and narrative synthesis.

Background: Symbol communication aids are used by children with little or no intelligible speech as an Augmentative and Alternative Communication strategy. Graphic symbols are used to help support understanding of language and used in symbol communication aids to support expressive communication. The decision making related to the selection of a symbol communication aid for a child is poorly understood and little is known about what language and communication attributes are considered in this selection.Aim: To identify from the literature the language or communication attributes of graphic symbol communication aids that currently influence AAC practice.Method and Procedure: A search strategy was developed and searches were performed on a range of electronic databases for papers published since 1970. Quality appraisal was carried out using the CCAT tool and papers rated as weak were not included in the review.Results: Eleven studies were included in the review reporting data from 66 participants. Weaknesses were identified in most studies that would limit the validity of the results for application to practice. Included studies investigated aspects of vocabulary organization and design, the process of vocabulary selection, and the choice of the symbol system and encoding method. Two studies also evaluated innovative communication aid attributes.Conclusions: Information from studies reported in the research literature provides a sparse source of information about symbol communication aids from which clinicians, children or family members may make informed decisions.Implications for RehabilitationThis review is the first to systematically appraise the literature to answer the question what evidence exists to inform clinical decision making in relation to the language or communication attributes of graphic symbol based communication aids? The review establishes that there is a paucity of evidence from studies and that these decisions must thus be based on other information and factors.The review does establish a small number of language or communication attributes of symbol communication aids, but no synthesis of the results of these studies was possible. This review thus suggests that vocabulary design and organization, symbol system and encoding method, and the choice of vocabulary selection method are attributes that clinicians may carefully review in order to inform decisions.Clinicians encountering symbol vocabulary packages claiming to be 'evidence based' should query the nature of this evidence.The rehabilitation research community should debate and develop appropriate research designs that will facilitate future robust studies investigating the effect of specific language or communication attributes of communication aids.