Deaf Native Signers Research Articles

Motor adaptation in deaf and hearing native signers.

Previous studies have suggested that deafness could lead to deficits in motor skills and other body-related abilities. However, the literature regarding motor skills in deaf adults is scarce and existing studies often included participants with heterogeneous language backgrounds and deafness etiologies, thus making it difficult to delineate the effects of deafness. In this study, we investigated motor learning in deaf native signers and hearing nonsigners. To isolate the effects of deafness and those of acquiring a signed language, we additionally tested a group of hearing native signers. Two well-established paradigms of motor learning were employed, in which participants had to adapt their hand movements to a rotation of the visual feedback (Experiment 1) or to the introduction of a force field (Experiment 2). Proprioceptive estimates were assessed before and after adaptation. Like hearing nonsigners, deaf and hearing signers showed robust adaptation in both motor adaptation paradigms. No significant differences in motor adaptation and memory were observed between deaf signers and hearing nonsigners, as well as between hearing signers and hearing nonsigners. Moreover, no discernible group differences in proprioceptive accuracy were observed. These findings challenge the prevalent notion that deafness leads to deficits in motor skills and other body-related abilities.

Impoverished language in early childhood affects the development of complex sentence structure.

The hypothesis that impoverished language experience affects complex sentence structure development around the end of early childhood was tested using a fully randomized, sentence-to-picture matching study in American Sign Language (ASL). The participants were ASL signers who had impoverished or typical access to language in early childhood. Deaf signers whose access to language was highly impoverished in early childhood (N=11) primarily comprehended structures consisting of a single verb and argument (Subject or Object), agreeing verbs, and the spatial relation or path of semantic classifiers. They showed difficulty comprehending more complex sentence structures involving dual lexical arguments or multiple verbs. As predicted, participants with typical language access in early childhood, deaf native signers (N=17) or hearing second-language learners (N=10), comprehended the range of 12 ASL sentence structures, independent of the subjective iconicity or frequency of the stimulus lexical items, or length of ASL experience and performance on non-verbal cognitive tasks. The results show that language experience in early childhood is necessary for the development of complex syntax. RESEARCH HIGHLIGHTS: Previous research with deaf signers suggests an inflection point around the end of early childhood for sentence structure development. Deaf signers who experienced impoverished language until the age of 9 or older comprehend several basic sentence structures but few complex structures. Language experience in early childhood is necessary for the development of complex sentence structure.

The Case of Mouth Action in Israeli Sign Language Discourse

This article discusses the function of a particular feature of sign language—mouth action—as it is expressed in various discourse contexts. Specifically, we examine forms of mouthing and mouth gesture as they are used in signed narrative and expository texts, highlighting the signers' choices during the production of these two text types. We propose a new perspective on mouth action types, relying on insights from the domain of discourse analysis combined with functional categories proposed in previous studies on mouth actions in sign languages. Six deaf native signers of Israeli Sign Language (ISL) produced twelve texts, yielding a corpus of 2,125 mouth actions (1,112 in narrative texts and 1,013 in expository texts). Our study points to both quantitative and qualitative differences in the use of mouth actions in the two text types. The findings emphasize the importance of the two types of mouth actions as essential means of decoding the message, and they highlight the way mouth actions serve the text and are affected by it.

BILINGUAL CURRICULUM MATERIALS SUPPORTING SIGNED LANGUAGE AS A FIRST LANGUAGE FOR DEAF STUDENTS

Considering Deaf children and adults as bilingual - their first language is a Signed Language (SL) and the second language is learned via print - provides professionals with a paradigm to be used for creating better learning opportunities. In this paper, Greek Sign Language ((G)SL)) [1] as a first language (L1) is the base language we use to present certain bilingual methodological teaching and learning considerations. This work is the result of a long journey from the initial thinking of the American Sign Language Curriculum and its influence on the development of the (G)SL curriculum in Greece. The paper offers discussion of innovative educational multimedia material that are easily accessed via online web portals, developed for teaching (G)SL as an L1 to pre-school and primary school Deaf children. In this work, SL as L1 is a resource that fully enables Deaf children to learn an L2 via print, supporting their bilingual acquisition capabilities. In developing curricula and supporting materials, we consider two important foundational components: Deaf native signers and near native signers as language role models for Deaf children, parents and teachers; and the development and interaction with digital educational materials. Thus, collaboration between educational and technology professionals and members of the Deaf community is critical. This bilingual model can be incorporated into any SL. (G)SL) is used as a model to display innovative practices merging SL (L1), print (L2), technology and creative instructional and assessment materials, maximized by understanding the visual nature of SL and its advantages for school learning. The penultimate goal is Deaf students to become successful bilingual learners to fully function in the world today and tomorrow.
 
 
 [1] In this paper, we will use (G)SL to indicate that we are discussing Greek Signed Language but content and technology can be used for any SL.

Culture is not destiny, for reading: highlighting variable routes to literacy within writing systems.

Cross-writing system research in psychology and cognitive neuroscience has yielded important findings regarding how a writing system's structure can influence the cognitive challenges of learning to read and the neural underpinnings of literacy. The current paper reviews these differences and extends the findings to demonstrate diversity in how skilled reading is accomplished within a single writing system, English. We argue that broad clusters of behavioral and neural patterns found across writing systems can also be found within subpopulations who display atypical routes to skilled English reading, subpopulations including Chinese-English bilinguals, deaf native signers, compensated readers, and distortion-sensitive readers. The patterns of interest include a tradeoff between the degree of reliance on phonological and morphological processing for skilled reading, a shift in attentional focus from smaller to larger orthographic units, and enhanced bilaterality of neural processing during word reading. Lastly, we consider how understanding atypical routes to reading may apply to other writing systems.

Event-related potential correlates of visuo-tactile motion processing in congenitally deaf humans

The impact of congenital deafness on the development of vision has been investigated to a considerable degree. However, whether multisensory processing is affected by auditory deprivation has often remained largely overlooked. To fill this gap, we investigated the consequences of a profound auditory deprivation from birth on visuo-tactile processing. While the electroencephalogram (EEG) was recorded, dynamic visuo-tactile stimuli with a congruent or an incongruent motion direction were presented to a group of congenitally deaf native signers (N = 21) and matched hearing controls (N = 21). Standard stimuli were moving continuously for 200 ms either upwards or downwards, whereas the motion of deviant stimuli was interrupted in one of the two modalities. Participants were asked to detect deviant stimuli, moving in a predefined direction while ignoring deviants moving in the non-target direction. Behaviorally, deaf individuals committed more false alarms than hearing controls in the incongruent condition, that is, they responded more often when deviants moved in the non-target motion direction. ERPs (140–164 ms) of the deaf group were more anteriorly distributed for the visuo-tactile stimulation in comparison to hearing controls. Moreover, visuo-tactile motion congruency effects emerged with a later latency in the deaf group (350–450 ms) than in the hearing control group (200–280 ms). These findings suggest altered selection strategies and neural correlates for visuo-tactile motion processing as a result of congenital deafness.

Developmental experiences alter the temporal processing characteristics of the visual cortex: Evidence from deaf and hearing native signers.

To date, the extent to which early experience shapes the functional characteristics of neural circuits is still a matter of debate. In the present study, we tested whether congenital deafness and/or the acquisition of a sign language alter the temporal processing characteristics of the visual system. Moreover, we investigated whether, assuming cross-modal plasticity in deaf individuals, the temporal processing characteristics of possibly reorganised auditory areas resemble those of the visual cortex. Steady-state visual evoked potentials (SSVEPs) were recorded in congenitally deaf native signers, hearing native signers, and hearing nonsigners. The luminance of the visual stimuli was periodically modulated at 12, 21, and 40 Hz. For hearing nonsigners, the optimal driving rate was 12 Hz. By contrast, for the group of hearing signers, the optimal driving rate was 12 and 21 Hz, whereas for the group of deaf signers, the optimal driving rate was 21 Hz. We did not observe evidence for cross-modal recruitment of auditory cortex in the group of deaf signers. These results suggest a higher preferred neural processing rate as a consequence of the acquisition of a sign language.

Emergence or Grammaticalization? The Case of Negation in Kata Kolok

Typological comparisons have revealed that signers can use manual elements and/or a non-manual marker to express standard negation, but little is known about how such systematic marking emerges from its gestural counterparts as a new sign language arises. We analyzed 1.73 h of spontaneous language data, featuring six deaf native signers from generations III-V of the sign language isolate Kata Kolok (Bali). These data show that Kata Kolok cannot be classified as a manual dominant or non-manual dominant sign language since both the manual negative sign and a side-to-side headshake are used extensively. Moreover, the intergenerational comparisons indicate a considerable increase in the use of headshake spreading for generation V which is unlikely to have resulted from contact with Indonesian Sign Language varieties. We also attest a specialized negative existential marker, namely, tongue protrusion, which does not appear in co-speech gesture in the surrounding community. We conclude that Kata Kolok is uniquely placed in the typological landscape of sign language negation, and that grammaticalization theory is essential to a deeper understanding of the emergence of grammatical structure from gesture.

The Cortical Organization of Syntactic Processing Is Supramodal: Evidence from American Sign Language.

Areas within the left-lateralized neural network for language have been found to be sensitive to syntactic complexity in spoken and written language. Previous research has revealed that these areas are active for sign language as well, but whether these areas are specifically responsive to syntactic complexity in sign language independent of lexical processing has yet to be found. To investigate the question, we used fMRI to neuroimage deaf native signers' comprehension of 180 sign strings in American Sign Language (ASL) with a picture-probe recognition task. The ASL strings were all six signs in length but varied at three levels of syntactic complexity: sign lists, two-word sentences, and complex sentences. Syntactic complexity significantly affected comprehension and memory, both behaviorally and neurally, by facilitating accuracy and response time on the picture-probe recognition task and eliciting a left lateralized activation response pattern in anterior and posterior superior temporal sulcus (aSTS and pSTS). Minimal or absent syntactic structure reduced picture-probe recognition and elicited activation in bilateral pSTS and occipital-temporal cortex. These results provide evidence from a sign language, ASL, that the combinatorial processing of anterior STS and pSTS is supramodal in nature. The results further suggest that the neurolinguistic processing of ASL is characterized by overlapping and separable neural systems for syntactic and lexical processing.

Enhanced biological motion perception in deaf native signers

We conducted two studies to test how deaf signed language users perceive biological motions. We created 18 Biological Motion point-light displays (PLDs) depicting everyday human actions, and 18 Scrambled control PLDs. First, we conducted an online behavioral rating survey, in which deaf and hearing raters identified the biological motion PLDs and rated how easy it was for them to identify the actions. Then, we conducted an EEG study in which Deaf Signers and Hearing Non-Signers watched both the Biological Motion PLDs and the Scrambled PLDs, and we computed the time-frequency responses within the theta, alpha, and beta EEG rhythms. From the behavioral rating task, we show that the deaf raters reported significantly less effort required for identifying the Biological motion PLDs, across all stimuli. The EEG results showed that the Deaf Signers showed theta, mu, and beta differentiation between Scrambled and Biological PLDs earlier and more consistently than Hearing Non-Signers. We conclude that native ASL users exhibit experience-dependent neuroplasticity in the domain of biological human motion perception.

When event knowledge overrides word order in sentence comprehension: Learning a first language after childhood.

Limited language experience in childhood is common among deaf individuals, which prior research has shown to lead to low levels of language processing. Although basic structures such as word order have been found to be resilient to conditions of sparse language input in early life, whether they are robust to conditions of extreme language delay is unknown. The sentence comprehension strategies of post-childhood, first-language (L1) learners of American Sign Language (ASL) with at least 9years of language experience were investigated, in comparison to two control groups of learners with full access to language from birth (deaf native signers and hearing L2 learners who were native English speakers). The results of a sentence-to-picture matching experiment show that event knowledge overrides word order for post-childhood L1 learners, regardless of the animacy of the subject, while both deaf native signers and hearing L2 signers consistently rely on word order to comprehend sentences. Language inaccessibility throughout early childhood impedes the acquisition of even basic word order. Similar to the strategies used by very young children prior to the development of basic sentence structure, post-childhood L1 learners rely more on context and event knowledge to comprehend sentences. Language experience during childhood is critical to the development of basic sentence structure.

Theory of Mind (ToM) Development in Thai Deaf Children.

This study explored theory of mind (ToM) development in school-aged deaf children. To address new questions, we gave a standard, well-controlled false-belief test to a large (n = 200) sample of severely-to-profoundly deaf children aged 8-15years in a non-Western culture (Thailand). There were 190 deaf children of hearing parents and 10 deaf native signers with signing deaf parents, consistent with overall population ratios. Comparing our Thai sample's ToM performance on standard tests of false-belief understanding with that reported in past studies, our results showed a 67% ToM success rate for Thai severely-to-profoundly deaf children of hearing parents similar to collective findings from past research on smaller samples in Australia, Estonia, France, Great Britain, Sweden, and the United States. Our Thai deaf native signers likewise performed equivalently to native signers of similar age studied in past research in Australia and the United States. Collectively, the detailed findings of our study suggest promising new directions for future studies to pursue in order to build upon this novel and theoretically provocative evidence about how ToM development and ToM delay unfold for school-aged deaf children growing up in varied cultures, school settings, and family circumstances.

The interaction of the visuo-spatial and the vestibular system depends on sensory experience in development

In hearing individuals, vestibular and visuo-spatial functions seem to be functionally linked. Previous studies have suggested that congenitally deaf individuals are at a higher risk for vestibular problems, which in hearing adults have often been found to be associated with impairments in visuo-spatial processing. However, communicating in a sign language provides extensive practice in visuo-spatial processing, which might counteract negative effects of vestibular impairments. Here, we investigated whether the functional link between vestibular and visuo-spatial functions is mandatory, that is whether it is impenetrable to experience or context, or whether it is dependent on specific sensory and cognitive experiences. To this end, we tested a group of congenitally deaf native signers and a group of hearing nonsigners on mental rotation and balance tasks. Compared to hearing nonsigners, mental rotation was superior in the deaf signers in conditions crucial for sign language comprehension. By contrast, the balance performance of the group of deaf signers was impaired. While in the group of hearing nonsigners, balance skills correlated with mental rotation abilities, no such relationship was observed in the group of deaf signers. These results suggest that the link between vestibular and visuo-spatial functions is not fixed but can be altered or even cancelled out by certain sensory or cognitive experiences, such as the acquisition of a sign language.

Fill the gap: A novel test to elicit nominal plurals in Sign Language of the Netherlands

The present study introduces a novel gap-filling test to elicit plural nouns in Sign Language of the Netherlands (NGT). As of yet, nominal plurals in NGT have not been described in detail, as eliciting plural nouns is not without challenges. In previous research on NGT (Zwitserlood and Nijhof 1999), native signers were asked to describe pictures of plural objects. However, when describing pictures, the signers automatically also expressed the spatial distribution of the objects depicted on the stimulus picture, using localization. As a consequence, it remains unclear what ‘pure’ plurals – without localization – look like. The goal of our gap-filling task is to disentangle pluralization from localization: participants are asked to insert plural nouns in signed sentence contexts where the spatial distribution of the referents is irrelevant. After piloting the task, five deaf native signers participated. The task succeeded in eliciting pure plural forms that were not spatially distributed, and the results show that NGT optionally employs reduplication to mark the pure plural of nouns. We conclude that our gap-filling task successfully controls for localization, targeting the desired structure without using written language. In future studies, the gap-filling task can be applied to other sign languages, targeting also other construction types.

Space Oddities: The Acquisition of Agreement Verbs by L2 Learners of Sign Language of the Netherlands

AbstractThis article reports the results of the first longitudinal study that systematically investigates the acquisition of verb agreement by hearing learners of a sign language. During a 2‐year period, 14 novel learners of Sign Language of the Netherlands (NGT) with a spoken language background performed an elicitation task 15 times. Seven deaf native signers and NGT teachers performed the same task to serve as a benchmark group. The results obtained show that for some learners, the verb agreement system of NGT was difficult to master, despite numerous examples in the input. As compared to the benchmark group, learners tended to omit agreement markers on verbs that could be modified, did not always correctly use established locations associated with discourse referents, and made characteristic errors with respect to properties that are important in the expression of agreement (movement and orientation). The outcomes of the study are of value to practitioners in the field, as they are informative with regard to the nature of the learning process during the first stages of learning a sign language.

Eyebrow position in grammatical and emotional expressions in Kazakh-Russian Sign Language: A quantitative study.

Facial expressions in sign languages are used to express grammatical functions, such as question marking, but can also be used to express emotions (either the signer's own or in constructed action contexts). Emotions and grammatical functions can utilize the same articulators, and the combinations can be congruent or incongruent. For instance, surprise and polar questions can be marked by raised eyebrows, while anger is usually marked by lowered eyebrows. We investigated what happens when different emotions (neutral/surprise/anger) are combined with different sentence types (statement/polar question/wh-question) in Kazakh-Russian Sign Language (KRSL), replicating studies previously made for other sign languages. We asked 9 native signers (5 deaf, 4 hearing children of deaf adults) to sign 10 simple sentences in 9 conditions (3 emotions * 3 sentence types). We used OpenPose software to track eyebrow position in the video recordings. We found that emotions and sentence types influence eyebrow position in KRSL: eyebrows are raised for polar questions and surprise, and lowered for anger. There are also some interactions between the two factors, as well as some differences between hearing and deaf native signers, namely a smaller effect of polar questions for the deaf group, and a different interaction between emotions and wh-question marking in the two groups. We thus find evidence for the complex influences on non-manual behavior in signers of sign languages, and showcase a quantitative approach to this field.

Effects of Early Language Deprivation on Brain Connectivity: Language Pathways in Deaf Native and Late First-Language Learners of American Sign Language.

Previous research has identified ventral and dorsal white matter tracts as being crucial for language processing; their maturation correlates with increased language processing capacity. Unknown is whether the growth or maintenance of these language-relevant pathways is shaped by language experience in early life. To investigate the effects of early language deprivation and the sensory-motor modality of language on white matter tracts, we examined the white matter connectivity of language-relevant pathways in congenitally deaf people with or without early access to language. We acquired diffusion tensor imaging (DTI) data from two groups of individuals who experienced language from birth, twelve deaf native signers of American Sign Language, and twelve hearing L2 signers of ASL (native English speakers), and from three, well-studied individual cases who experienced minimal language during childhood. The results indicate that the sensory-motor modality of early language experience does not affect the white matter microstructure between crucial language regions. Both groups with early language experience, deaf and hearing, show leftward laterality in the two language-related tracts. However, all three cases with early language deprivation showed altered white matter microstructure, especially in the left dorsal arcuate fasciculus (AF) pathway.

Neural correlates of semantic and syntactic processing in German Sign Language

The study of deaf and hearing native users of signed languages can offer unique insights into how biological constraints and environmental input interact to shape the neural bases of language processing. Here, we use functional magnetic resonance imaging (fMRI) to address two questions: (1) Do semantic and syntactic processing in a signed language rely on anatomically and functionally distinct neural substrates as it has been shown for spoken languages? and (2) Does hearing status affect the neural correlates of these two types of linguistic processing? Deaf and hearing native signers performed a sentence judgement task on German Sign Language (Deutsche Gebärdensprache: DGS) sentences which were correct or contained either syntactic or semantic violations. We hypothesized that processing of semantic and syntactic violations in DGS relies on distinct neural substrates as it has been shown for spoken languages. Moreover, we hypothesized that effects of hearing status are observed within auditory regions, as deaf native signers have been shown to activate auditory areas to a greater extent than hearing native signers when processing a signed language. Semantic processing activated low-level visual areas and the left inferior frontal gyrus (IFG), suggesting both modality-dependent and independent processing mechanisms. Syntactic processing elicited increased activation in the right supramarginal gyrus (SMG). Moreover, psychophysiological interaction (PPI) analyses revealed a cluster in left middle occipital regions showing increased functional coupling with the right SMG during syntactic relative to semantic processing, possibly indicating spatial processing mechanisms that are specific to signed syntax. Effects of hearing status were observed in the right superior temporal cortex (STC): deaf but not hearing native signers showed greater activation for semantic violations than for syntactic violations in this region. Taken together, the present findings suggest that the neural correlates of language processing are partly determined by biological constraints, but that they may additionally be influenced by the unique processing demands of the language modality and different sensory experiences.

Executive Function in Deaf Children: Auditory Access and Language Access.

Deaf children are frequently reported to be at risk for difficulties in executive function (EF); however, the literature is divided over whether these difficulties are the result of deafness itself or of delays/deficits in language that often co-occur with deafness. The purpose of this study is to discriminate these hypotheses by assessing EF in populations where the 2 accounts make contrasting predictions. We use a between-groups design involving 116 children, ages 5-12 years, across 3 groups: (a) participants with normal hearing (n = 45), (b) deaf native signers who had access to American Sign Language from birth (n = 45), and (c) oral cochlear implant users who did not have full access to language prior to cochlear implantation (n = 26). Measures include both parent report and performance-based assessments of EF. Parent report results suggest that early access to language has a stronger impact on EF than early access to sound. Performance-based results trended in a similar direction, but no between-group differences were significant. These results indicate that healthy EF skills do not require audition and therefore that difficulties in this domain do not result primarily from a lack of auditory experience. Instead, results are consistent with the hypothesis that language proficiency, whether in sign or speech, is crucial for the development of healthy EF. Further research is needed to test whether sign language proficiency also confers benefits to deaf children from hearing families.

Inferencing in Deaf Adolescents during Sign-Supported Speech Comprehension

ABSTRACTWe tested the capability of deaf adolescents, including a group of users of cochlear implants, to generate inferences during spoken language comprehension and whether they benefited from the use of sign-supported speech (SSS). Stimuli consisted of 24 short video-recorded texts in spoken language and in SSS. Participants responded to literal and inferential multiple-choice questions. In spoken language cochlear implant users had more difficulty in processing inferential than literal information and found predictive inferences harder than associative inferences. The level of spoken language proficiency was related to inference generation, especially for predictive inferences. Similarly, deaf native signers had more difficulties in generating predictive inferences, although SSS increased their comprehension. Lip-reading skills and working memory were positively related to accuracy in SSS. The inclusion of SSS only had a positive impact on the comprehension of native signers. Results suggest that cochlear implant users would benefit from an intervention to enhance verbal skills.