Is Semantics Affected by Missing a Critical Period? Evidence from the Persian Deaf

The present study aims to explore the semantic knowledge of a group of Iranian deaf individuals who, due mainly to auditory deprivation did not acquire language normally in early years of their life. The participants were ten deaf and a matched number of hearing individuals as control group. A test of five tasks was administrated to assess their knowledge of vocabulary, collocation, semantic categorizations, semantic features, and proverbs. Although the results indicated a significant difference between the deaf and the hearing group, a between- group comparison of each task revealed no significant difference between the deaf and hearing participants in the number of errors in vocabulary, collocations, semantic categorization, and semantic features. The only task in which deaf participants did significantly worse than the control group was that of proverbs. Therefore, it could be argued that, language deprivation in early childhood does not have the same effect on different components of our linguistic knowledge and that the acquisition of semantics may well continue beyond puberty.     

Cognitive consequences of congenital deafness

Comparing congenitally deaf children with hearing children on a variety of information processing tasks provides a natural test of the developmental consequences accompanying the long term loss of a particular sensory input. In this experiment, two sequential and two spatial tasks were used to evaluate the way deaf and hearing individuals process these different types of information. When deaf students were asked to recall the order of a string of lights, they performed as well as hearing students. Deaf students were at a significant disadvantage, however, when processing sequentially presented digits. Deaf students performed as well as hearing students on two complex, standardized spatial tasks. The loss of a major sensory modality had minimal effect on three of the four tasks investigated in the present study. Explanations for the single task with a performance differential are considered.     

Neural substrates for verbal working memory in deaf signers: fMRI study and lesion case report

The nature of the representations maintained in verbal working memory is a topic of debate. Some authors argue for a modality-dependent code, tied to particular sensory or motor systems. Others argue for a modality-neutral code. Sign language affords a unique perspective because it factors out the effects of modality. In an fMRI experiment, deaf participants viewed and covertly rehearsed strings of non-sense signs; analyses focused on regions responsive in both sensory and rehearsal phases. Compared with previous findings in hearing subjects, deaf subjects showed a significantly increased involvement of parietal regions. A lesion case study indicates that this network is left-dominant. The findings support the hypothesis that linguistic working memory is supported by modality-specific neural systems, but some modality-neutral systems may also be involved.     

Temporal processing in deaf signers

The auditory and visual modalities differ in their capacities for temporal analysis, and speech relies on more rapid temporal contrasts than does sign language. We examined whether congenitally deaf signers show enhanced or diminished capacities for processing rapidly varying visual signals in light of the differences in sensory and language experience of deaf and hearing individuals. Four experiments compared rapid temporal analysis in deaf signers and hearing subjects at three different levels: sensation, perception, and memory. Experiment 1 measured critical flicker frequency thresholds and Experiment 2, two-point thresholds to a flashing light. Experiments 3-4 investigated perception and memory for the temporal order of rapidly varying nonlinguistic visual forms. In contrast to certain previous studies, specifically those investigating the effects of short-term sensory deprivation, no significant differences between deaf and hearing subjects were found at any level. Deaf signers do not show diminished capacities for rapid temporal analysis, in comparison to hearing individuals. The data also suggest that the deficits in rapid temporal analysis reported previously for children with developmental language delay cannot be attributed to lack of experience with speech processing and production.     

Left-Hemisphere Dominance for Motion Processing in Deaf Signers

Evidence from neurophysiological studies in animals as well as humans has demonstrated robust changes in neural organization and function following early-onset sensory deprivation. Unfortunately, the perceptual consequences of these changes remain largely unexplored. The study of deaf individuals who have been auditorily deprived since birth and who rely on a visual language (i.e., American Sign Language, ASL) for communication affords a unique opportunity to investigate the degree to which perception in the remaining, intact senses (e.g., vision) is modified as a result of altered sensory and language experience. We studied visual motion perception in deaf individuals and compared their performance with that of hearing subjects. Thresholds and reaction times were obtained for a motion discrimination task, in both central and peripheral vision. Although deaf and hearing subjects had comparable absolute scores on this task, a robust and intriguing difference was found regarding relative performance for left-visual-field (LVF) versus right-visual-field (RVF) stimuli: Whereas hearing subjects exhibited a slight LVF advantage, the deaf exhibited a strong RVF advantage. Thus, for deaf subjects, the left hemisphere may be specialized for motion processing. These results suggest that perceptual processes required for the acquisition and comprehension of language (motion processing, in the case of ASL) are recruited (or "captured") by the left, language-dominant hemisphere.     

Semantic and surface codes in the memory of deaf children

In three experiments, deaf children in the age range of 6 years, 10 months to 15 years, 5 months were presented with continuous lists of items, and for each item they had to indicate whether it had appeared before on the list. Later items were related to preceding items either in surface form or in meaning or were unrelated. False-recognition errors (i.e., “yes” responses to new items) served as an index of memorial coding. In one experiment, the items presented to the subjects were printed words. The results of this experiment showed a false-recognition effect (i.e., more errors to related words than to unrelated words) for both semantically related words and orthographically similar words. In the other two experiments, the subjects viewed a series of manual signs on videotape. In these experiments, there was a false-recognition effect for signs related semantically and for signs related cherologically (i.e., similar in terms of their manual production). These results establish orthography and cherology as effective memorial codes for deaf children. The finding of a consistently strong semantic effect for young deaf children stands in contrast to findings of weak semantic effects in false-recognition studies with young hearing children. The ascendancy of semantic codes for deaf children was attributed to the absence of competition from the speech code which dominates the linguistic memory of hearing children.     

Provision of Genetic Services for Hearing Loss: Results from a National Survey and Comparison to Insights Obtained from Previous Focus Group Discussions

Hearing loss is a common sensory deficit and more than 50% of affected individuals have a genetic etiology. The discovery of 40 genes and more than 100 loci involved in hearing loss has made genetic testing for some of these genes widely available. Genetic services for deafness are also being sought more often due to the early identification of hearing loss through newborn screening services. The motivations for pursuing genetic testing, and how genetic services are provided to the client may differ among individuals. Additionally, information obtained through genetic testing can be perceived and used in different ways by parents of deaf children and deaf adults. This study aimed to follow up on focus group studies published earlier with a quantitative survey instrument and assess the preference of consumers for provision of genetic services. We conducted a national survey of hearing and deaf parents of children with hearing loss and of deaf adults. Data was compared and analyzed by hearing status of the participant, their community affiliation and the genetic testing status using nominal logistic regression. Consistent with our focus group results, the survey participants thought that a genetic counselor/geneticist would be the most appropriate professional to provide genetics services. Statistically significant differences were noted in the preferred choice of provider based on the genetic testing status. Parents preferred that genetic evaluation, including testing, occur either immediately at or a few months after the audiologic diagnosis of hearing loss. This data should help providers in clinical genetics keep patient preferences at the helm and provide culturally competent services.     

Neural Systems Mediating American Sign Language: Effects of Sensory Experience and Age of Acquisition

ERPs were recorded from deaf and hearing native signers and from hearing subjects who acquired ASL late or not at all as they viewed ASL signs that formed sentences. The results were compared across these groups and with those from hearing subjects reading English sentences. The results suggest that there are constraints on the organization of the neural systems that mediate formal languages and that these are independent of the modality through which language is acquired. These include different specializations of anterior and posterior cortical regions in aspects of grammatical and semantic processing and a bias for the left hemisphere to mediate aspects of mnemonic functions in language. Additionally, the results suggest that the nature and timing of sensory and language experience significantly impact the development of the language systems of the brain. Effects of the early acquisition of ASL include an increased role for the right hemisphere and for parietal cortex and this occurs in both hearing and deaf native signers. An increased role of posterior temporal and occipital areas occurs in deaf native signers only and thus may be attributable to auditory deprivation.     

Hearing-Loss Effects on a Procedural Task Sequence

40 deaf and 40 hearing children representing 2 age groups were blindfolded and presented with 3 high-relief finger mazes of increasing complexity. It was found that young deaf children performed the most difficult task more efficiently than comparable hearing children. Contrary to previous findings, hearing children showed no advantage over deaf children on any of the three tasks as a result of their supposed greater facility with verbal conceptual mediators. The results were interpreted as supporting the idea that deaf children compensate for their auditory lack and verbal deficiency by developing problem solving skills that maximize sensitivity to other sensory modalities.     

Intellectual functioning of deaf adults and children: Answers and questions

Intelligence has long been seen as linked to the spoken and written word. Because most deaf people have poor spoken language skills and find reading a significant challenge, there is a history in both psychology and education of considering deaf individuals to be less intelligent or less cognitively flexible than hearing individuals. With progress in understanding natural signed languages and cognitive abilities of individuals who lack spoken language, this perspective has changed. We now recognise, for example, that deaf people have some advantages in visuospatial ability relative to hearing people, and there is a link between the use of natural signed languages and enhanced visuospatial abilities in several domains. Such findings contrast with results found in memory, where the modality of mental representation, experience, and organisation of knowledge lead to differences in performance between deaf and hearing individuals, usually in favour of the latter. Such findings demonstrate that hearing loss and use of a natural sign language can influence intellectual abilities, including many tapped by standardised IQ tests. These findings raise interesting questions about the place of spoken language in our understanding of intelligence and ways in which we can use basic research for applied purposes.     

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。     

Cerebral lateralization of deaf and hearing individuals for linguistic comparison judgments.

A group of congenitally deaf adults and a group of hearing adults, both fluent in sign language, were tested to determine cerebral lateralization. In the most revealing task, subjects were given a series of trials in which they were fist presented with a videotaped sign and then with a word exposed tachistoscopically to the right visual field or left visual field, and were required to judge whether the word corresponded to the sign or not. The results suggested that the comparison processes involved in the decision were performed more efficiently by the left hemisphere for hearing subjects and by the right hemisphere for deaf subjects. However, the deaf subjects performed as well as the hearing subjects in the left hemisphere, suggesting that the deaf are not impeded by their auditory-speech handicap from developing the left hemisphere for at least some types of linguistic processing.     

Modality effects: Do they fall on deaf ears?

The present study tests the assumption of the PAS theory of echoic memory (Greene & Crowder, 1984) that the representation of acoustic features is necessary in producing modality effects. Performance by deaf subjects was compared to hearing subjects on serial and free-recall tasks with vocalizing and non-vocalizing conditions. For the serial tasks, typical modality and acoustic similarity effects were observed with hearing subjects, and no such effects were found with deaf subjects. However, for the free-recall task, modality effects were found for both deaf and hearing subjects. It is unlikely that phonological coding resulting from gestural cues mediates the modality effect, as phonological confusion errors for deaf and hearing subjects did not correlate with the size of this effect.     

Determinants of spelling ability in deaf and hearing adults: Access to linguistic structure

The extent to which ability to access linguistic regularities of the orthography is dependent on spoken language was investigated in a two-part spelling test administered to both hearing and profoundly deaf college students. The spelling test examined ability to spell words varying in the degree to which their correct orthographic representation could be derived from the linguistic structure of English. Both groups of subjects were found to be sensitive to the underlying regularities of the orthography as indicated by greater accuracy on linguistically-derivable words than on irregular words. Comparison of accuracy on a production task and on a multiple-choice recognition task showed that the performance of both deaf and hearing subjects benefited from the recognition format, but especially so in the spelling of irregular words. Differences in the underlying spelling process for deaf and hearing spellers were revealed in an analysis of their misspellings: Deaf subjects produced fewer phonetically accurate misspellings than did the hearing subjects. Nonetheless, the deaf spellers tended to observe the formational constraints of English phonology and morphology in their misspellings. Together, these results suggest that deaf subjects are able to develop an appreciation for the structural properties of the orthography, but that their spelling may be guided by an accurate representation of the phonetic structure of words to a lesser degree than it is for hearing spellers.     

Processing a dynamic visual—Spatial language: Psycholinguistic studies of American Sign Language

American Sign Language (ASL) has evolved within a completely different biological medium, using the hands and face rather than the vocal tract and perceived by eye rather than by ear. The research reviewed in this article addresses the consequences of this different modality for language processing, linguistic structure, and spatial cognition. Language modality appears to affect aspects of lexical recognition and the nature of the grammatical form used for reference. Select aspects of nonlinguistic spatial cognition (visual imagery and face discrimination) appear to be enhanced in deaf and hearing ASL signers. It is hypothesized that this enhancement is due to experience with a visual-spatial language and is tied to specific linguistic processing requirements (interpretation of grammatical facial expression, perspective transformations, and the use of topographic classifiers). In addition, adult deaf signers differ in the age at which they were first exposed to ASL during childhood. The effect of late acquisition of language on linguistic processing is investigated in several studies. The results show selective effects of late exposure to ASL on language processing, independent of grammatical knowledge.This research was supported in part by National Institutes of Health grant HD-13249 awarded to Ursula Bellugi and Karen Emmorey, as well as NIH grants DC-00146, DC-00201, and HD-26022. I would like to thank and acknowledge Ursula Bellugi for her collaboration during much of the research described in this article.     

Visual movement perception in deaf and hearing individuals

A number of studies have investigated changes in the perception of visual motion as a result of altered sensory experiences. An animal study has shown that auditory-deprived cats exhibit enhanced performance in a visual movement detection task compared to hearing cats (Lomber, Meredith, & Kral, 2010). In humans, the behavioural evidence regarding the perception of motion is less clear. The present study investigated deaf and hearing adult participants using a movement localization task and a direction of motion task employing coherently-moving and static visual dot patterns. Overall, deaf and hearing participants did not differ in their movement localization performance, although within the deaf group, a left visual field advantage was found. When discriminating the direction of motion, however, deaf participants responded faster and tended to be more accurate when detecting small differences in direction compared with the hearing controls. These results conform to the view that visual abilities are enhanced after auditory deprivation and extend previous findings regarding visual motion processing in deaf individuals.     

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.     

Deaf signers and serial recall in the visual modality: Memory for signs,fingerspelling, and print

This study investigated serial recall by congenitally, profoundly deaf signers for visually specified linguistic information presented in their primary language, American Sign Language (ASL), and in printed or fingerspelled English. There were three main findings. First, differences in the serial-position curves across these conditions distinguished the changing-state stimuli from the static stimuli. These differences were a recency advantage and a primacy disadvantage for the ASL signs and fingerspelled English words, relative to the printed English words. Second, the deaf subjects, who were college students and graduates, used a sign-based code to recall ASL signs, but not to recall English words; this result suggests that well-educated deaf signers do not translate into their primary language when the information to be recalled is in English. Finally, mean recall of the deaf subjects for ordered lists of ASL signs and fingerspelled and printed English words was significantly less than that of hearing control subjects for the printed words; this difference may be explained by the particular efficacy of a speech-based code used by hearing individuals for retention of ordered linguistic information and by the relatively limited speech experience of congenitally, profoundly deaf individuals.     

Deaf murderers: clinical and forensic issues

Data are reported on 28 deaf individuals who were convicted, pled guilty, or have been charged and awaiting trial for murder. The unique forensic issues raised by these cases are discussed, and their clinical picture presented. A significant percentage of these deaf murderers and defendants had such severely limited communication skills in both English and American Sign Language that they lacked the linguistic ability to understand the charges against them and/or to participate in their own defense. As such, they were incompetent to stand trial, due not to mental illness or mental retardation, but to linguistic deficits. This form of incompetence poses a dilemma to the courts that remains unresolved. This same linguistic disability makes it impossible for some deaf suspects to be administered Miranda Warnings in a way comprehensible to them. This paper identifies the reasons for the communication problems many deaf persons face in court and offers remedial steps to help assure fair trials and police interrogations for deaf defendants. The roles and responsibilities of psychiatric and psychological experts in these cases are discussed. Data are provided on the etiology of the 28 individuals' hearing losses, psychiatric/psychological histories, IQs, communication characteristics, educational levels, and victim characteristics.