Speech lateralization in deaf populations: evidence for a developmental critical period

Cerebral lateralization for speech in right-handed normal hearing and deaf adolescents was assessed using the dual-task paradigm. Subjects with normal hearing and deafness acquired after 3 years of age displayed left hemispheric dominance for speech production, whereas both congenitally deaf and those with an early acquired deafness (onset 6-36 months) showed atypical, anomalous cerebral representation. These results suggest the presence of a developmental critical period for cerebral lateralization during which exposure to adequate environmental stimulation may be needed to activate left hemispheric dominance for speech.     

The effects of linguistic experience on cerebral lateralization for speech production in normal hearing and deaf adolescents

The cerebral lateralization patterns for speech production in 57 normal hearing and deaf adolescents were studied using the dual-task paradigm. Normal hearing subjects showed left hemispheric dominance for speech production, whereas both the congenitally deaf and those with early acquired deafness showed atypical cerebral representation for speech production. Deaf subjects whose hearing loss occurred after 2 years of age displayed a pattern of mixed cerebral dominance related to complexity of speech production or task difficulty. These results are interpreted as evidence for a relationship between linguistic/cognitive stage of development and the ontogenesis of cerebral lateralization. A parallel lateralization hypothesis of left cerebral dominance for speech production is offered.     

Linguistic flexibility in signed and written language productions of deaf children

Linguistic flexibility of deaf and hearing children was compared by examining the relative frequencies of their nonliteral constructions in stories written and signed (by the deaf) or written and spoken (by the hearing). Seven types of nonliteral constructions were considered: novel figurative language, frozen figurative language, gestures, pantomime, linguistic modifications, linguistic inventions, and lexical substitutions. Among the hearing 8- to 15-year-olds, oral and written stories contained comparable numbers of nonliteral constructions. Among their age-matched deaf peers, however, nonliteral constructions were significantly stories contained comparable numbers of nonliteral constructions. Among their age-matched deaf peers, however, nonliteral constructions were significantly more common in signed than written stories. Overall, hearing students used more nonliteral constructions in their written stories than did their deaf peers (who used very few), whereas deaf students used more nonliteral constructions in their signed stories than their hearing peers did in their spoken stories. The results suggest that deaf children are linguistically and cognitively more competent than is generally assumed on the basis of evaluations in English. Although inferior to hearing age-mates in written expression, they are comparable to, and in some ways better than those peers when evaluated using their primary mode of communication.     

Disordered Communication and Grieving in Deaf Member Families

When a deaf child is born to hearing parents, a grieving process is initiated in the parents. Unresolved grieving over their child's deafness often makes it difficult for hearing parents to accept the importance of signing, thus increasing the child's problems — further source of grief for these parents. Clinical illustrations are provided of (1) the reciprocal relationship between disruption of the mourning process and disturbance of communication between family members, and (2) the transmission of the dysfunctional relationship between hearing parents and deaf children to the subsequent relationship between the deaf children, when they reach adulthood, and their hearing children.     

The gestures ASL signers use tell us when they are ready to learn math

The manual gestures that hearing children produce when explaining their answers to math problems predict whether they will profit from instruction in those problems. We ask here whether gesture plays a similar role in deaf children, whose primary communication system is in the manual modality. Forty ASL-signing deaf children explained their solutions to math problems and were then given instruction in those problems. Children who produced many gestures conveying different information from their signs (gesture-sign mismatches) were more likely to succeed after instruction than children who produced few, suggesting that mismatch can occur within-modality, and paving the way for using gesture-based teaching strategies with deaf learners.     

Effects of signability and imagery on word recall of deaf and hearing students

This study examined 40 deaf and 20 hearing students' free recall of visually presented words varied systematically with respect to signability (i.e., words that could be expressed by a single sign) and visual imagery. Half of the deaf subjects had deaf parents, while the other half had hearing parents. For deaf students, recall was better for words that had sign-language equivalents and high-imagery values. For the hearing students, recall was better for words with high-imagery values, but there was no effect of signability. Over-all, the hearing students recalled significantly more words than the deaf students in both immediate and delayed free-recall conditions. In immediate recall, deaf students with deaf parents reported using a sign-language coding strategy more frequently and recalled more words correctly than deaf students with hearing parents. Serial-position curves indicated several differences in patterns of recall among the groups. These results underline the importance of sign language in the memory and recall of deaf persons.     

Cerebral lateralization of language in deaf and hearing people

In Experiment 1 neither hearing nor prelingually deaf signing adolescents showed marked lateralization for lexical decision but, unlike the hearing, the deaf were not impaired by the introduction of pseudohomophones. In Experiment 2 semantic categorization produced a left hemisphere advantage in the hearing for words but not pictures whereas in the deaf words and signs but not pictures showed a right hemisphere advantage. In Experiment 3 the lexical decision and semantic categorization findings were confirmed and both groups showed a right hemisphere advantage for a face/nonface decision task. The possible effect of initial language acquisition on the development of hemispheric lateralization for language is discussed.     

Does language about similarity play a role in fostering similarity comparison in children?

Commenting on perceptual similarities between objects stands out as an important linguistic achievement, one that may pave the way towards noticing and commenting on more abstract relational commonalities between objects. To explore whether having a conventional linguistic system is necessary for children to comment on different types of similarity comparisons, we observed four children who had not been exposed to usable linguistic input - deaf children whose hearing losses prevented them from learning spoken language and whose hearing parents had not exposed them to sign language. These children developed gesture systems that have language-like structure at many different levels. Here we ask whether the deaf children used their gestures to comment on similarity relations and, if so, which types of relations they expressed. We found that all four deaf children were able to use their gestures to express similarity comparisons (point to cat + point to tiger) resembling those conveyed by 40 hearing children in early gesture + speech combinations (cat + point to tiger). However, the two groups diverged at later ages. Hearing children, after acquiring the word like, shifted from primarily expressing global similarity (as in cat/tiger) to primarily expressing single-property similarity (as in crayon is brown like my hair). In contrast, the deaf children, lacking an explicit term for similarity, continued to primarily express global similarity. The findings underscore the robustness of similarity comparisons in human communication, but also highlight the importance of conventional terms for comparison as likely contributors to routinely expressing more focused similarity relations.     

Recognition of affective and noncanonical linguistic facial expressions in hearing and deaf subjects

This study explores the use of two types of facial expressions, linguistic and affective, in a lateralized recognition accuracy test with hearing and deaf subjects. The linguistic expressions represent unfamiliar facial expression for the hearing subjects whereas they serve as meaningful linguistic emblems for deaf signers. Hearing subjects showed left visual field advantages for both types of signals while deaf subjects' visual field asymmetries were greatly influenced by the order of presentation. The results suggest that for hearing persons, the right hemisphere may predominate in the recognition of all forms of facial expression. For deaf signers, hemispheric specialization for the processing of facial signals may be influenced by the differences these signals serve in this population. The use of noncanonical facial signals in laterality paradigms is encouraged as it provides an additional avenue of exploration into the underlying determinants of hemispheric specialization for recognition of facial expression.     

First‐hand sensory experience plays a limited role in children's early understanding of seeing and hearing as sources of knowledge: Evidence from typically hearing and deaf children

One early‐developing component of theory of mind is an understanding of the link between sensory perception and knowledge formation. We know little about the extent to which children's first‐hand sensory experiences drive the development of this understanding, as most tasks capturing this early understanding target vision, with less attention paid to the other senses. In this study, 64 typically hearing children (M_age = 4.0 years) and 21 orally educated deaf children (M_age = 5.44 years) were asked to identify which of two informants knew the identity of a toy animal when each had differing perceptual access to the animal. In the ‘seeing’ condition, one informant saw the animal and the other did not; in the ‘hearing’ condition, one informant heard the animal and the other did not. For both hearing and deaf children, there was no difference between performance on hearing and seeing trials, but deaf children were delayed in both conditions. Further, within both the hearing and deaf groups, older children outperformed younger children on these tasks, indicating that there is a developmental progression. Taken together, the pattern of results suggests that experiences other than first‐hand sensory experiences drive children's developing understanding that sensory perception is associated with knowledge.     

Exploring perceptual processing of ASL and human actions: effects of inversion and repetition priming

In this paper, we compare responses of deaf signers and hearing non-signers engaged in a categorization task of signs and non-linguistic human actions. We examine the time it takes to make such categorizations under conditions of 180° stimulus inversion and as a function of repetition priming, in an effort to understand whether the processing of sign language forms draws upon special processing mechanisms or makes use of mechanisms used in recognition of non-linguistic human actions. Our data show that deaf signers were much faster in the categorization of both linguistic and non-linguistic actions, and relative to hearing non-signers, show evidence that they were more sensitive to the configural properties of signs. Our study suggests that sign expertise may lead to modifications of a general-purpose human action recognition system rather than evoking a qualitatively different mode of processing, and supports the contention that signed languages make use of perceptual systems through which humans understand or parse human actions and gestures more generally.     

Language First: Deaf Children from Deaf Families Spontaneously Anticipate False Beliefs

ABSTRACT

Being connected to other people at the level of inner and unobservable mental states is one of the most essential aspects of a meaningful life, including psychological well-being and successful cooperation. The foundation for this kind of connectedness is our theory of mind (ToM), that is the ability to understand our own and others’ inner experiences in terms of mental states such as beliefs and desires. But how do we develop this ability? Forty-six 17- to 107-months-old children completed a non-verbal eye-tracker false-belief task. There were 9 signing deaf children from deaf families and two comparison groups, that is 13 deaf children with cochlear implants and 24 typically developing hearing children. We show that typically developing hearing children and deaf children from deaf families, but not deaf children with cochlear implants, succeeded on a non-verbal eye-tracking ToM task. The findings suggest that the ability to recognize others’ mental states is supported by very early, continuous and fluent language-based communication with caregivers.     

听觉障碍对聋人视觉功能影响的理论之争：缺陷还是补偿？

听觉通道受损,是否会影响聋人的视觉功能？有三种理论对此做出了解释。缺陷理论：聋人视觉功能存在缺陷,包括听觉脚手架假说和劳动分工假说。补偿理论：聋人视觉功能会表现出增强,包括响应增强假说、知觉增强假说、超通道功能假说和背侧通路假说。整合理论：聋人视觉功能既可能表现为缺陷,也可能表现为增强,与实验任务和被试年龄有关。本文评述了听觉障碍对聋人视觉功能影响的三种理论,并对其今后的发展趋势进行了展望。     

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, do extra-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.     

Subliminal priming and effects of hand dominance

In the masked priming paradigm, motor responses to targets are influenced by previously presented subliminal primes, and are guided by facilitatory and inhibitory mechanisms that depend on prime-target compatibility/duration. In this study, we evaluate subliminal-driven priming in right- and left-handers during unimanual as well as bimanual tasks. The data from the unimanual tasks confirmed that prime-target compatibility affects performance as a function of prime-target duration. In a bimanual setting, the preferred hand benefitted from facilitation in both handedness groups whereas the non-preferred hand showed a positive priming effect only in left-handers. This denotes that left-handers are more susceptible to response activation of either hand. In addition, inhibitory priming had a stronger effect on the non-preferred than preferred hand, independent of handedness group. Overall, the findings suggest that subliminal-driven mechanisms that assist adaptive motor behavior are sensitive not only to extrinsic (task-related) factors such as prime-target compatibility but also to intrinsic (performer-related) factors such as hand dominance. The data further provide support for handedness-specific effects in motor functions and underline a significant role of hand dominance in the control of bimanual actions.     

Performance Asymmetries in Computer Mouse Control of Right-Handers, and Left-Handers with Left- and Right-Handed Mouse Experience

Precision and general computer mouse aiming performance by right-handers (RH-RM) and left-handers with right-handed mouse experience (LH-RM) and by left-handers with left-handed mouse experience (LH-LM) were compared. A number of performance measures, such as reaction time, time to reach a target, time to click on target, and cursor trajectory, were analyzed. Superficially, specific hand experience seemed to dictate performance asymmetries, but a closer look revealed interactions between hand preference and hand performance. That finding has implications for theories of handedness. In addition, precision and general directional aiming with the mouse cursor showed a clear right hand superiority in reaction time in both RH-RM and LH-RM subjects, whereas LH-LM subjects showed no lateral asymmetries. Finally, the overall time taken for the task, averaged across groups and conditions, favored the experienced hand by some 180 ms. In practical terms, that is not a large difference, especially because the difference will be reduced with practice. Thus, the use of the inexperienced hand can be advocated when there is a need to forestall or ameliorate repetitive stress in the experienced hand.     

The distribution and development of handedness for manual gestures in captive chimpanzees (Pan troglodytes)

This article describes the distribution and development of handedness for manual gestures in captive chimpanzees. Data on handedness for unimanual gestures were collected in a sample of 227 captive chimpanzees. Handedness for these gestures was compared with handedness for three other measures of hand use: tool use, reaching, and coordinated bimanual actions. Chimpanzees were significantly more right-handed for gestures than for all other measures of hand use. Hand use for simple reaching at 3 to 4 years of age predicted hand use for gestures 10 years later. Use of the right hand for gestures was significantly higher when gestures were accompanied by a vocalization than when they were not. The collective results suggest that left-hemisphere specialization for language may have evolved initially from asymmetries in manual gestures in the common ancestor of chimpanzees and humans, rather than from hand use associated with other, non-communicative motor actions, including tool use and coordinated bimanual actions, as has been previously suggested in the literature.     

Development of social-cognitive and communication skills in children born deaf

Central to the interface of social-cognitive and communicative development is the growth of a theory of mind (ToM). ToM is mastered by most hearing children and deaf children of signing deaf parents by the age of 5 or 6 but is often seriously delayed in deaf children of hearing parents. This paper reviews recently published research on deaf children's ToM development and presents an original study consisting of eight longitudinal case histories that collectively map late-signing deaf children's ToM performance from 44 to 158 months of age. While five tentative conclusions can be posited from the collective research so far, further investigation of each of these possibilities is clearly needed.     

Semantic and formational clustering in deaf and hearing subjects’ free recall of signs

To investigate whether formational properties of sign language are used spontaneously to organize long-term memory, 16 deaf college students were given a free recall task with items that could be categorized either by shared semantic category or by shared sign language hand shape. Both presentation and response modes (signed or written) were varied between subjects. Analyses revealed no effects of mode on trials to criterion or number of items recalled at 1 week. The clustering that occurred was exclusively semantic, with significantly higher clustering scores during acquisition trials in subjects required to sign their responses. In Experiment 2, formational clustering was encouraged by including formational similarity as the only experimenter-defined basis of categorization, by increasing formational similarity within categories, and by testing only subjects with high signing skills. Input and output modes were again varied between subjects. Subjects were deaf college students with deaf parents (n = 10) or hearing parents (n = 16), and hearing adults with deaf parents (n = 8). Again, spontaneous clustering by formational similarity was extremely low. In only one case— deaf subjects with hearing parents given signed input—did formational clustering increase significantly across the eight acquisition trials. After the categorical nature of the list was explained to subjects at a 1-week retention session, all groups clustered output by formational categories. Apparently, fluent signers do have knowledge of the formational structure of signs, but do not spontaneously use this knowledge as a basis of mnemonic organization in long-term memory.