Considering Communication Disorders and Differences in the Signed Language Modality

David Quinto-Pozos

Introduction

Over five decades of inquiry into signed languages have allowed language and communication researchers to expand what is known about structural variation and human language, patterns of language learning, and the cognitive processing of language by children and adults. Surprisingly, comparatively little work during this same period has focused on signed language communication disorders even though there are likely thousands of signed language users (including school-aged children) throughout the world who possess some type of signed language deficit. Perhaps one reason for the lack of research on this topic lies in a major challenge faced by researchers. Specifically, there is much variation among deaf signers with respect to whether they have language input from models who are fluent in a signed language; this is true both for first exposure and for regular interaction with native or native-like language users. For many deaf children atypicality has been viewed as simply a developmental phase – something that is expected to 'go away' as they get older. Unfortunately, this view has resulted, at least in some cases, in late identification of linguistic and/or cognitive deficits that could have been addressed earlier. This chapter and this volume are intended to serve as a resource for researchers and clinicians on the topic of signed language communication disorders, and on the question of how disorders of visual language might be considered within the contexts of deaf, hard of hearing and hearing individuals who acquire and use a signed language.

Similarities and Differences Across Modalities

A major question within this area of inquiry is the following: how are signed language communication disorders similar to or different from spoken language communication disorders? Recent writings have also addressed this question (Woll, 2012; Woll & Morgan, 2012). Presumably, we should expect multiple parallels across disorders of signed and spoken languages because of similarities between signed and spoken language structures and between the ways in which both types of languages are acquired by children. However, we might also expect characteristics of each modality to influence the types of communication disorders that appear in signers and speakers; some possible areas of consideration include the linguistic signal, the articulators used for language, and the articulator space. See Table 1.1 for a summary of the comparisons. In this section, sign and speech are compared in order to provide the researcher, the student and the practitioner with a way to consider possibilities for communication disorders in signed languages.

Similarities

Signed languages are natural languages that are structurally similar to spoken languages

For decades, research has shown that signed languages are natural languages that can be described with reference to levels of structure that characterize spoken language such as phonology, morphology, syntax and semantics/pragmatics (see, for example, Brentari, 2012; Emmorey, 2002; Johnston & Schembri, 2007; Klima & Bellugi, 1979; Sandler & Lillo-Martin, 2006; Woll & Sutton-Spence, 1999). For example, lexical signs can be broken down into multiple phonological units with handshape, place of articulation, movement and palm orientation values specifying how a sign is to be articulated. Linguistic descriptions of signed minimal pairs and performance-based slips of the hand (i.e. errors where target phonological features of a sign are incorrectly produced) provide evidence for the sublexical structure of sign (Hohenberger et al., 2002; Klima & Bellugi, 1979). Many authors have suggested that the movement of a sign is a key feature of signed syllables, although there is less agreement about the internal structure of the signed syllable (see Emmorey, 2007; Jantunen & Takkinen, 2010; Wilbur & Allen, 1991; Wilbur & Petersen, 1997). Consistent with the sublexical structure of signs, phonological disorders (e.g. Broomfield & Dodd, 2001) may appear in certain signers, with characteristic errors in one or more phonological values within signs (also see Corina, 1998 for paraphasias in adult aphasics). One report of children's deficits with signed phonological structure appears in Quinto-Pozos et al. (2011), in which second-hand accounts of deaf children who struggle with movement, place of articulation and palm orientation of signs are described. For that study, the authors interviewed professionals at bilingual (ASL-English) schools for the Deaf about their experiences with native signing deaf children who appear to be struggling with the acquisition of American Sign Language (ASL).

Evidence of struggles with aspects of signed language phonology can be found in the language production of children who have been diagnosed with autism spectrum disorder (ASD). In the current volume, Shield and Meier describe incorrect palm orientation or movement values that are produced by deaf children with ASD. For example, rather than fingerspelling with the palm facing toward an interlocutor, they sometimes have their hand turned toward themselves. This type of error is apparently unattested in typically developing children over the age of 18 months of age. The authors argue that the palm orientation errors during sign production are evidence of impaired perspective-taking abilities for the ASD children. A learner of a signed language must attend to orientation of the palm (i.e. the direction in which the palm is facing) in order to correctly produce a sign, since signs look rather different to the addressee than they do to the...