American Sign Language Users Research Articles

Discourse Deficits Following Right Hemisphere Damage in Deaf Signers

Previous findings have demonstrated that hemispheric organization in deaf users of American Sign Language (ASL) parallels that of the hearing population, with the left hemisphere showing dominance for grammatical linguistic functions and the right hemisphere showing specialization for non-linguistic spatial functions. The present study addresses two further questions: first, doextra-grammatical discourse functions in deaf signers show the same right-hemisphere dominance observed for discourse functions in hearing subjects; and second, do discourse functions in ASL that employ spatial relations depend upon more general intact spatial cognitive abilities? We report findings from two right-hemisphere damaged deaf signers, both of whom show disruption of discourse functions in absence of any disruption of grammatical functions. The exact nature of the disruption differs for the two subjects, however. Subject AR shows difficulty in maintaining topical coherence, while SJ shows difficulty in employing spatial discourse devices. Further, the two subjects are equally impaired on non-linguistic spatial tasks, indicating that spared spatial discourse functions can occur even when more general spatial cognition is disrupted. We conclude that, as in the hearing population, discourse functions involve the right hemisphere; that distinct discourse functions can be dissociated from one another in ASL; and that brain organization for linguistic spatial devices is driven by its functional role in language processing, rather than by its surface, spatial characteristics.

Mental rotation within linguistic and non-linguistic domains in users of American sign language

American sign language (ASL) uses space itself to encode spatial information. Spatial scenes are most often described from the perspective of the person signing (the `narrator'), such that the viewer must perform what amounts to a 180° mental rotation to correctly comprehend the description. But scenes can also be described, non-canonically, from the viewer's perspective, in which case no rotation is required. Is mental rotation during sign language processing difficult for ASL signers? Are there differences between linguistic and non-linguistic mental rotation? Experiment 1 required subjects to decide whether a signed description matched a room presented on videotape. Deaf ASL signers were more accurate when viewing scenes described from the narrator's perspective (even though rotation is required) than from the viewer's perspective (no rotation required). In Experiment 2, deaf signers and hearing non-signers viewed videotapes of objects appearing briefly and sequentially on a board marked with an entrance. This board either matched an identical board in front of the subject or was rotated 180°. Subjects were asked to place objects on their board in the orientation and location shown on the video, making the appropriate rotation when required. All subjects were significantly less accurate when rotation was required, but ASL signers performed significantly better than hearing non-signers under rotation. ASL signers were also more accurate in remembering object orientation. Signers then viewed a video in which the same scenes were signed from the two perspectives (i.e. rotation required or no rotation required). In contrast to their performance with real objects, signers did not show the typical mental rotation effect. Males outperformed females on the rotation task with objects, but the superiority disappeared in the linguistic condition. We discuss the nature of the ASL mental rotation transformation, and we conclude that habitual use of ASL can enhance non-linguistic cognitive processes thus providing evidence for (a form of) the linguistic relativity hypothesis.

A "word length effect" for sign language: further evidence for the role of language in structuring working memory.

We report a sign length effect in deaf users of American Sign Language that is analogous to the word length effect for speech. Lists containing long signs (signs that traverse relatively long distances) produced poorer memory performance than did lists of short signs (signs that do not change in location). Further, this length effect was eliminated by articulatory suppression (repetitive motion of the hands), and articulatory suppression produced an overall drop in performance. The pattern of results, together with previous findings (Wilson & Emmorey, 1997), provides evidence for a working memory system for sign language that consists of a phonological storage buffer and an articulatory rehearsal mechanism. This indicates a close equivalence of structure between working memory for sign language and working memory for speech. The implications of this equivalence are discussed.

Modality of Language Shapes Working Memory: Evidence From Digit Span and Spatial Span in ASL Signers

Deaf children who are native users of American Sign Language (ASL) and hearing children who are native English speakers performed three working memory tasks. Results indicate that language modality shapes the architecture of working memory. Digit span with forward and backward report, performed by each group in their native language, suggests that the language rehearsal mechanisms for spoken language and for sign language differ in their processing constraints. Unlike hearing children, deaf children who are native signers of ASL were as good at backward recall of digits as at forward recall, suggesting that serial order information for ASL is stored in a form that does not have a preferred directionality. Data from a group of deaf children who were not native signers of ASL rule out explanations in terms of a floor effect or a nonlinguistic visual strategy. Further, deaf children who were native signers outperformed hearing children on a nonlinguistic spatial memory task, suggesting that language expertise in a particular modality exerts an influence on nonlinguistic working memory within that modality. Thus, language modality has consequences for the structure of working memory, both within and outside the linguistic domain.

Working Memory for Sign Language: A Window Into the Architecture of the Working Memory System

Traditionally, working memory has been divided into two major domains: verbal and visuo-spatial. The verbal domain of working memory can be characterized either by its relationship to language or by its grounding in auditory processing. Because of this ambiguity, languages that are not auditory and vocal (i.e., signed languages) pose a challenge to this conception of working memory. We describe several experiments with deaf users of American Sign Language (ASL) that explore the extent to which the architecture of working memory is determined by the constraints of auditory and visual processing and the extent to which it is determined by the characteristics of language. Various working memory effects were investigated: phonological similarity, word length, and articulatory suppression. The pattern of evidence strongly supports the existence of a sign-based 'rehearsal loop' mechanism parallel to the speech-based rehearsal loop. However, we also discuss evidence pointing to differences between the speech loop and the sign loop from forward and backward digit span tasks with deaf and hearing subjects. Despite their similarities based on linguistic properties, the speech loop and the sign loop appear to diverge due to the differing processing demands of audition and vision. Overall, the results suggest that the architecture of working memory is shaped both by the properties of language structure and by the constraints imposed by sensorimotor modality.

The signer effect on MMPI performance of deaf respondents.

In order to determine the existence of a signer effect, two videotapes of the same 38 Minnesota Multiphasic Personality Inventory (MMPI) critical items, translated into American Sign Language (ASL) and signed by different signers, were administered to 35 deaf adults. Results of this study demonstrate an insignificant signer effect and underscore the potential utility and practicality of future ASL translations of self-report tests for use with deaf individuals. Caveats for future translations include the necessity for constant attention to translation refinements and for utilizing native ASL users with appropriate training in psychology as signers.

Pragmatic and Linguistic Constraints on Message Formulation

This study provides a cross-linguistic replication, using American Sign Language (ASL), of the Brown and Dell (1987) finding that when relaying an action involving an instrument, English speakers are more likely to explicitly mention the instrument if it is atypically, rather than typically, used to accomplish that action. Subjects were 20 hearing-impaired users of English and 20 hearing-impaired users of ASL. Each subject read and retold, in either English or ASL, 20 short stories. Analyses of the stories revealed production decision differences between ASL and English, but no differences related to hearing status. In ASL, there is more explicitness, and importance seems to play a more pivotal role in instrument specification. The results are related to differences in the typology of English and ASL and are discussed with regard to second-language learning and translation.

Hand dominance for signing: Clues to brain lateralization of language

Virtually all right-handed individuals are left hemisphere dominant for language. Sign languages of the deaf provide an unusual vehicle for exploring the link between handedness and hemispheric specialization for language the hands themselves are the language articulators. Performance of the right and left hand was examined in deaf native users of American Sign Language(ASL) for speeded production of one-handed signs and for shadowing of signed discourse. Opposite patterns of asymmetries in hand performance were found in right- and left- handers. However, left-handers were more flexible than right-handers in signing with their non- preferred hand. Furthermore, unusual patterns of hand use for sign were found in a deaf signer with a left hemisphere lesion, possibly indexing increased mediation of the intacthemisphere. Implications for brain organization of language in a visual—gestural mode are discussed.

Identification and discrimination of handshape in American Sign Language.

Lane, Boyes-Braem, and Bellugi (1976) suggested that American Sign Language (ASL) was perceived according to distinctive features, as is the case with speech. They advanced a binary model of distinctive features for one component of ASL signs, handshape. To test the validity of this model, three native users of ASL and three English speakers who knew no ASL participated in two experiments. In the first, subjects identified ASL handshapes obscured by visual noise, and confusion frequencies yielded similarity scores for all possible pairs of handshapes. Pairs that shared more features according to the model produced higher similarity scores for both groups of subjects. In the second experiment, subjects discriminated a subset of all possible handshape pairs in a speeded “same-different” task; discrimination accuracy and reaction times yielded a d’ and a ds value, respectively, for each pair. Pairs that shared more features according to a slightly revised version of the model produced lower discrimination indices for both groups. While the binary model was supported, a model in which handshape features varied continuously in two dimensions was more consistent with all sets of data. Both models describe hearing and deaf performance equally well, suggesting that linguistic experience does little to alter perception of the visual features germane to handshape identification and discrimination.

Perception of sign language from an array of 27 moving spots

Many deaf people in the USA communicate in American sign language (ASL), which has an expressive capacity equivalent to that of spoken language, although structurally independent of spoken languages. It comprises hand and arm movements often combined with particular facial gestures; together these are sufficiently precise to transmit all the complexities and innuendoes of language. Here we demonstrate that fluent ASL users can communicate easily when all they see of each other is an array of 27 light spots strategically placed on the hands and face. The results indicate the salient locations in normal sign perception, and suggest that it is feasible to transmit sign using the bandwidth of one telephone line rather than a much more expensive TV line.

The invariance of sentence performance structures across language modality.

Native users of American Sign Language were asked to manipulate sentences in four different ways: sign them at slow rate, parse them, make relatedness judgments of pairs of signs taken from each sentence, and recall the sentences. The data obtained from these four tasks (pause durations, parsing values, indices of relatedness and probe latencies) were used to construct hierarchical performance structures for each of the sentences. The resulting structures were highly similar across tasks; that is, performance structures are not task specific. The four measures at each sign boundary in each sentence were well predicted by a performance model, elaborated by Grosjean, Grosjean, and Lane for speech, that combines a parsing measure with a symmetry measure. Thus performance structures appear to be founded in the processing of language, be it visual or oral, and not in the properties of any particular communication modality.

Intelligibility and comprehension of time compressed sign language narratives.

A method of time compressing visual displays was devised to assess the effects of compression on the comprehension of American sign language (ASL). Two ASL narratives were visually presented to three groups of deaf ASL users. A compression group was presented narratives compressed to 50% of the duration of the normal rates. A no-compression group was presented narratives signed at normal rates. A pause groups was presented compressed narratives with blank pauses inserted so that the total time per narrative was equal to that of the no-compression versions. Following each narrative, subjects completed a written comprehension task. Comprehension in both compression and pause groups was significantly lower than in the no-compression group. Pauses did not significantly affect scores relative to compression. An additional group of deaf ASL users was presented an intelligibility task in which signs taken from the narratives were presented in isolation either with or without compression. The total number of signs correctly identified was significantly lower with compression. Decrements in comprehension were best explained as the result of cumulative decrements in sign intelligibility and not as the result of decrements in available processing time.

Cerebral asymmetry in the perception of American Sign Language

American Sign Language (ASL) offers a valuable opportunity for the study of cerebral asymmetries, since it incorporates both language structure and complex spatial relations: processing the former has generally been considered a left-hemisphere function, the latter, a right-hemisphere one. To study such asymmetries, congenitally deaf, native ASL users and normally-hearing English speakers unfamiliar with ASL were asked to identify four kinds of stimuli: signs from ASL, handshapes never used in ASL, Arabic digits, and random geometric forms. Stimuli were presented tachistoscopically to a visual hemifield and subjects manually responded as rapidly as possible to specified targets. Both deaf and hearing subjects showed left-visual-field (hence, presumably right-hemisphere) advantages to the signs and to the non-ASL hands. The hearing subjects, further, showed a left-hemisphere advantage to the Arabic numbers, while the deaf subjects showed no reliable visual-field differences to this material. We infer that the spatial processing required of the signs predominated over their language processing in determining the cerebral asymmetry of the deaf for these stimuli.

The effect of sign language grammatical structure on recall

The nature of grammatical structure in American Sign Language (ASL) was investigated using a short-term free-recall paradigm. Grammatical signed sentences and random strings of ASL signs were visually presented to 60 deaf ASL users. Either a nonsense sign or a finger-spelled consonant-vowel-consonant (CVC) was embedded in each string. The number of nonsense items recalled and the total number of signs recalled were significantly greater for grammatical strings than for random strings. The results extend previous findings and suggest that, as in speech, grammatical structure is actively utilized in the processing of ASL, serving to increase the efficiency of such processing.

Communication of Agent, Object, and Indirect Object in Signed and Spoken Languages

A picture-description task was used to study the comparative effectiveness of communication between deaf subjects using American Sign Language, and hearing subjects using spoken English: 16 deaf, native users of American Sign Language and 16 hearing, native users of English. All subjects were university undergraduate students. Within the two groups, paired subjects alternately described pictures to each other. Pictures illustrated three different characters assuming in turn the roles of agent, object, and indirect object. Following a description by Subject1, Subject2 selected the picture he or she thought Subject1 had described, from a set of 6 pictures containing the described picture. The frequency of errors did not differ significantly between signing and speaking subjects.