Production and comprehension of graphic symbol utterances expressing complex propositions by adults who use augmentative and alternative communication systems

We explored production and comprehension of complex sentences constructed using a limited vocabulary on a graphic symbol display with voice output by 25 adults who use augmentative and alternative communication. When asked to construct subject (SS) and object (OS) relative clause sentences, only a minority of participants encoded SS and OS relative clause sentences using different word orders. When asked to interpret graphic symbol utterances, most participants chose an SS interpretation. Thus, the word order used most frequently in production appeared to have a single preferred interpretation. The relationship between the word orders produced in graphic symbol utterances and the way the same word orders are interpreted is not necessarily straightforward.