Signed Language Pathology

Articles considering the emerging concept of signed language pathology have identified a variety of signed language disorders, such as signed aphasia, signed stuttering, specific signed language impairment, signed language learning disability, and signed language delay. The diagnosis and treatment of these disorders can be seen as parallel to the field of speech-language pathology. Just as the field of speech-language pathology includes both skills of identifying diagnoses and prescribing therapeutic treatment, the emerging field of signed language pathology must also include both disciplines. Much has been written describing and identifying potential diagnoses for disorders of signed language; less has been written regarding suggestions for treatment.

Aphasia is generally defined as the deterioration of communication due to acquired damage to the nervous system, involving the processes of comprehending and producing linguistic discourse. Researchers have identified difficulties among deaf individuals with damage in their left cerebral hemisphere (i.e., Broca and/or Wernicke regions) in producing and comprehending signed language. As of 2014, there were approximately 5,000 deaf stroke survivors in the United States, and it is believed that one fifth of them have aphasia. Ursula Bellugi and colleagues at the Salk Institute have been studying this phenomenon since the 1970s and have identified the following features that characterize signed aphasia:

• halting and effortful sign production;
• single-sign utterances;
• absence of syntactical and morphological markings;
• disordered grammatical markings such as errors in spatialized markings;
• producing errors with handshape(s), location(s), and movement(s) when signing;
• production errors with the sublexical, lexical, and sentence-level processes; and
• poor comprehension when perceiving signed lexicons and sentences.

Stuttering is typically defined as a speech disorder characterized by disrupted rhythm or dysfluency. Studies on signed stuttering began as early as the late 1930s. Greg Snyder identified that signed stuttering exists as a disorder indicative of processing errors and functions as a cognitive disorder. While it is known that there are signers who stutter, no statistical data are available for this population. Characteristics of signed stuttering include

• manual repetitions;
• prolongations;
• blocks;
• choppy manipulations;
• jerky and hesitant signs, frequently at the beginning of an utterance;
• involuntary interjections; and
• extra movements as found in natural signed languages around the world.

Specific signed language impairment (SSLI) is considered an isolated linguistic problem involving phonology, morphology, syntax, semantics, pragmatics, or listening and expressing signed language. This is found in children with atypical signed language development with no other obvious impairments. Few research studies have addressed SSLI among deaf children and adults. The diagnosis of SSLI first appeared in the United Kingdom among a small number of deaf students, and has been studied in American Sign Language (ASL) recently by David Quinto-Pozos and colleagues. No data could be found regarding the prevalence of SSLI. Preliminary findings indicate that the characteristics of SSLI include

• performance within normal ranges on various tests of nonverbal intelligence and motor dexterity, but poor performance on linguistic tests that target signed language competencies;
• impairment of narrative skills as well as knowledge and use of signed language grammar; and
• difficulties processing rapid temporal changes that characterize sign production, linked to the management of linguistic structures.

A signed language learning disability (SLLD) may be characterized by struggles in the cognitive ability to learn signed language. SLLD encompasses a broad range of learning issues, including decoding, whereas signed aphasia, signed stuttering, and SSLI describe specific neurological language impairments. Research in this area is still emerging. Professionals unfamiliar with ASL have misdiagnosed countless deaf children as having learning disabilities over several decades. Recent research has shown that there is a distinct SLLD that appears among deaf children, which

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