Phonological Errors in the Signing of Deaf Autistic Children: More Evidence for a Self-Other Mapping Deficit

Background: Poor imitation of other people's bodily movements (gestures and/or actions) is one characteristic of people with autism (Smith & Bryson, 1994; Williams et al., 2004). However, researchers have failed to reach a consensus about the exact nature of this imitation deficit. Some researchers (e.g., Rogers et al., 1996; Green et al., 2002) have argued that the addition of meaning facilitates gesture imitation, but this assertion has been contradicted by other studies (Mostofsky et al, 2006). In evaluating six different proposals from the literature, Williams et al. (2004) concluded that a deficit in “self-other mapping ability” is the most likely explanation for the imitation deficit in autism. Self-other mapping (Rogers & Pennington, 1991) is the ability to relate one's own movements to the movements observed in others. The most striking evidence derives from studies in which autistic subjects produced “reversal errors” during imitation; e.g., they reproduced gestures with palm reversed or reversed direction of movement, seeming to indicate an inability to adopt the perspective of the person being imitated (Ohta, 1987; Brown, 1996; Hobson & Lee, 1999; Whiten & Brown, 1999). Objectives: The signing and imitation skills of deaf autistic children have never been systematically examined. Sign-learning children must imitate the body movements of others in order to learn lexical items. Thus, sign depends crucially on skills that may be impaired in autism. If autism entails a deficit in self-other mapping, then the signing of deaf autistic children could show evidence of this at the phonological (articulatory) level. Though phonology is a relative strength of hearing autistic children learning speech (Minshew et al., 1995), self-other mappings are needed to learn the phonological forms of some basic signs, such as those specified for inward/outward palm orientation, like the American Sign Language (ASL) signs WEDNESDAY and BATHROOM. Our objective in this research is to investigate whether there is evidence of a self-other mapping deficit in the lexical phonology of deaf autistic children. Methods: We tested a group of 10 deaf children of deaf parents (DoD) diagnosed with autism (age range: 4;7 to 16;3; M=9;6) and a control group of 13 typically-developing (TD) DoD children (age range: 3;7 to 6;9; M=4;9) on a sign elicitation task, an imitation task of nonsense signs, and a fingerspelling task. Items were coded for reversals on the palm orientation parameter, and the Freeman-Halton extension of the Fisher exact probability test was performed to detect group differences. Results: The autistic group made significantly more palm orientation errors than the TD group (p < .005). Age was a significant factor, with younger autistic children (under 10) making more reversals than older autistic children and TD children. Conclusions: These results are consistent with the hypothesis that the imitation deficit in autism reflects an impairment in self-other mapping. Further, they do not support the hypothesis that the addition of meaning facilitates gesture imitation in autism. This study shows that, unlike speech, an impairment in self-other mapping has consequences for basic phonological development in sign.