Autism spectrum disorder (ASD) consists of a set of neurobiological developmental disorders characterized by communicative and social deficits as well as repetitive, stereotyped behaviors. It is estimated that ASD affects approximately 1 in 88 children in the United States (Centers for Disease Control, 2012
). The prevalence of congenital deafness is much lower, estimated at 1 to 6 per 1,000 newborns (Cunningham & Cox, 2003
; Kemper & Downs, 2000
). However, ASD appears to be more frequent in the deaf population than in the general population; Szymanski, Brice, Lam, and Hotto (2012)
reported that 1 in 59 deaf or hard of hearing children in the 2009–2010 Annual Survey of Deaf and Hard of Hearing Children and Youth (Gallaudet Research Institute, 2011
) carried an ASD diagnosis. At least two other studies have found that a higher-than-expected percentage of deaf children in their samples had ASD (7%: Chess, Fernandez, & Korn, 1978
; 4%: Jure, Rapin, & Tuchman, 1991
). Conversely, there is evidence that severe hearing loss occurs in the ASD population at a rate of about ten times that in the general population (Rosenhall, Nordin, Sandström, Ahlsén, & Gillberg, 1999
Despite the fact that language deficits form one of the core symptoms of ASD, very little research has investigated the sign language development of deaf children with ASD. Most prior studies on signing and ASD focused on the teaching of signs to hearing children with severe ASD and little speech (for reviews, see Bonvillian, Nelson, & Rhyne, 1981
; Carr, 1979
). Some, but not all, nonverbal hearing children with ASD were able to learn and use some manual signs, even when prior speech training had failed (e.g., Fulwiler & Fouts, 1976
). However, most of these children did not progress beyond the use of a small number of signs. Moreover, the sign vocabulary sizes claimed in the literature may be considerably overstated, as most signs trained to criterion in such studies were not observed outside training sessions in spontaneous usage (Bonvillian & Blackburn, 1991
: 276). Previous work with hearing children has also examined the relationship between motor deficits in ASD and sign acquisition. In a study on 14 nonverbal hearing students with severe ASD (mean age 13;8), Seal and Bonvillian (1997)
found that sign formation accuracy was highly correlated with fine motor age and apraxia, suggesting that sign formation errors could in part be a result of underlying motor deficits.
Just as most research on the use of sign language in ASD has focused on hearing children, most research on the acquisition of signed languages has focused on typically-developing deaf children (for summaries, see Emmorey, 2002
; Newport & Meier, 1986
). The scant literature on the signing of deaf people with ASD includes a brief report of a single 21-year-old deaf signer with autism, whose echolalia was contrasted with the agrammatism of a signer with Broca's aphasia (Poizner, Klima, & Bellugi, 1990
). Morgan and colleagues have reported extensively on the acquisition of British Sign Language (BSL) by Christopher, a hearing language savant who lacks an ASD diagnosis but exhibits characteristics typical of autism (Morgan, Smith, Tsimpli, & Woll, 2002
; Smith, Tsimpli, Morgan, & Woll, 2011
). Recently, Denmark (2011)
investigated the comprehension and production of affective and linguistic facial expression in deaf British signers with ASD.
The sign language of children with ASD is of theoretical interest because sign language acquisition depends crucially on social and cognitive skills known to be impaired in ASD. For example, children with ASD are impaired in their comprehension of facial expressions (Grossman & Tager-Flusberg, 2008
; Lacroix, Guidetti, Rogé, & Reilly, 2009
; Rump, Giovannelli, Minshew, & Strauss, 2009
; Volker, Lopata, Smith, & Thomeer, 2009
), yet facial expressions signal questions, conditionals, and other aspects of sign language grammar (Liddell, 1980
). The imitation of signs in three-dimensional space could also pose problems for children with ASD, whose deficits in theory of mind and/or perspective-taking (e.g., Baron-Cohen, Leslie, & Frith, 1985
; Hamilton, Brindley, & Frith, 2009
) could impede the recognition and reproduction of signs viewed from varying angles in everyday life.
Previous work (Williams, Whiten, & Singh, 2004
for a review) has found that hearing children with ASD are impaired in their ability to imitate the body movements of others; this impairment might have particular bearing on the acquisition of sign by children with ASD. A compelling finding from a number of studies is that hearing children with ASD tend to reverse the direction of observed palm orientations when imitating the gestures of others. Ohta (1987)
was the first to report such errors (which he called “partial imitations”): children with ASD often imitated a wave-like gesture (in which the experimenter's open palm was oriented toward the child) with their palms facing inward toward themselves. In another study, Smith and Bryson (1998)
found that, in the imitation of 8 ASL handshapes and 8 bimanual gestures, hearing children with ASD made significantly more 180° reversal errors (e.g., palm toward the viewer rather than away from him) than age-matched language-impaired and typically-developing children. These reversed palm orientations suggest that children with ASD imitate gestures as they appear from their own perspective. Williams et al. conclude that such errors are evidence of an autism-specific deficit in “self–other mapping,” that is, a deficit in the process(es) by which children and adults observe the movements of others and map them onto their own bodies (Rogers & Pennington, 1991
The acquisition of signs could likewise be affected by a deficit in self-other mapping, inasmuch as the learning of signs entails the imitation of the bodily movements of others. Specifically, signs in ASL that are specified for an inward or outward palm orientation, for example tuesday1
(), could exhibit reversal errors. The sign tuesday
is produced with the palm facing inward toward the signer's body; a child facing the signer sees the back of the signer's hand. If that child reproduced what he saw from his own perspective, the child would articulate the sign with his palm facing away from his body; as a result, the child would see the back of his own hand. Interestingly, such a reversal could lead to lexical confusion in ASL, since the signs tuesday
are near-minimal pairs that differ primarily in the direction the palm faces. Not all signs pose this problem: we would not predict palm orientation errors on signs with the palm facing up or down, for example, since an upward facing palm appears upward no matter the viewer's angle on it. Thus, the imitation of upward or downward palm orientation (and the learning of signs specified for such palm orientations) is not complicated by the varying configurations of signers and learners in a three-dimensional world.
The ASL signs TUESDAY (left) and BATHROOM (right).
In a preliminary pilot study, we observed one five-year-old deaf child (of hearing parents) who had been identified as having ASD by administrators of the residential school for the Deaf he attended. As we had no access to his educational records, we could not verify this diagnosis. However, in two videotaped naturalistic observation sessions (a 27-minute session at age 5;3 and a 24-minute session at age 5;5), this child produced 46 palm orientation errors in a corpus of 171 sign tokens. Twenty-eight of the 46 errors involved an inward/outward palm reversal. Most of these tokens were signs for days of the week, on which his palm faced outward rather than inward, and signs for numbers, on which his palm faced downward toward the table rather than inward. This evidence suggested that it would be worth exploring the production of signs by signing children with ASD.
In this paper, we ask whether the reversal errors reported in the gesture imitation of hearing children with ASD will also be produced by children with ASD who have been exposed from birth to ASL by their deaf parents. The vast majority of deaf children are born to hearing parents (90–95%; Mitchell & Karchmer, 2004
) and may exhibit linguistic and cognitive delays due to impoverished or delayed language exposure (Schick, de Villiers, de Villiers, & Hoffmeister, 2007
) that could mask the effects of ASD. Crucially, children born to deaf parents have access to excellent sign language models from birth.
If ASD entails a deficit in self-other mapping, and self-other mapping is a general cognitive mechanism that affects linguistic and non-linguistic domains alike, then we would predict the appearance of palm reversal errors in the signing of children with ASD. Alternatively, native exposure to a sign language might lead to enhanced visuo-spatial abilities (cf. Bosworth & Dobkins, 2002
), which could attenuate the effects of such a deficit. In this case, palm reversals would not be evident in the signing of such children.
We report two studies of a sample of five signing children with ASD (four deaf children of deaf parents and one hearing child of deaf parents) and compare their performance to a sample of 12 typically-developing deaf children of deaf parents.