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.     

Listening comprehension and working memory are impaired in attention-deficit hyperactivity disorder irrespective of language impairment

This study investigated listening comprehension and working memory abilities in children with attention-deficit hyperactivity disorder (ADHD), presenting with and without language impairments (LI). A 4-group design classified a community sample (n = 77) of boys aged 9–12 into ADHD, ADHD + LI, LI, and Normal groups. Children completed tests of basic language and cognitive skills, verbal and spatial working memory, and passage-level listening comprehension. Multivariate analyses and post hoc comparisons indicated that ADHD children who did not have co-occurring LI comprehended factual information from spoken passages as well as normal children, but were poorer at comprehending inferences and monitoring comprehension of instructions. ADHD children did not differ from normal children in verbal span, but showed significantly poorer verbal working memory, spatial span, and spatial working memory. The ADHD + LI and LI groups were most impaired in listening comprehension and working memory performance, but did not differ from each other. Listening comprehension skills were significantly correlated with both verbal and spatial working memory, and parent–teacher ratings of inattention and hyperactivity/impulsivity. Findings that children with ADHD but no LI showed subtle higher-level listening comprehension deficits have implications for both current diagnostic practices and conceptualizations of ADHD.     

Phonological Working Memory and Spoken Language Development in Young Children

This study investigated the relationship between phonological working memory and spoken language development in a large unselected sample of 4- and 5-year old children. Assessments were made of the language produced by the children on the Bus Story (Renfrew, 1969), a standard test of continuous speech. In this test, children listen to a story, which they then recount with the aid of visual clues. The amount of information recalled and the average length of the five longest utterances are taken as indices of children's expressive language abilities. Phonological working memory skills were indexed by memory span and the ability to repeat non-words. The ability to repeat non-words made a significant contribution to the variance in the children's speech independently of age, vocabulary knowledge, and nonverbal cognitive skills. The possible mechanisms by which skills assessed by phonological memory tasks may be linked to the development of speech production abilities are considered.     

Implicit statistical learning in language processing: Word predictability is the key

Fundamental learning abilities related to the implicit encoding of sequential structure have been postulated to underlie language acquisition and processing. However, there is very little direct evidence to date supporting such a link between implicit statistical learning and language. In three experiments using novel methods of assessing implicit learning and language abilities, we show that sensitivity to sequential structure – as measured by improvements to immediate memory span for structurally-consistent input sequences – is significantly correlated with the ability to use knowledge of word predictability to aid speech perception under degraded listening conditions. Importantly, the association remained even after controlling for participant performance on other cognitive tasks, including short-term and working memory, intelligence, attention and inhibition, and vocabulary knowledge. Thus, the evidence suggests that implicit learning abilities are essential for acquiring long-term knowledge of the sequential structure of language – i.e., knowledge of word predictability – and that individual differences on such abilities impact speech perception in everyday situations. These findings provide a new theoretical rationale linking basic learning phenomena to specific aspects of spoken language processing in adults, and may furthermore indicate new fruitful directions for investigating both typical and atypical language development.     

How grammar can cope with limited short-term memory: simultaneity and seriality in sign languages

It is known that in American Sign Language (ASL) span is shorter than in English, but this discrepancy has never been systematically investigated using other pairs of signed and spoken languages. This finding is at odds with results showing that short-term memory (STM) for signs has an internal organization similar to STM for words. Moreover, some methodological questions remain open. Thus, we measured span of deaf and matched hearing participants for Italian Sign Language (LIS) and Italian, respectively, controlling for all the possible variables that might be responsible for the discrepancy: yet, a difference in span between deaf signers and hearing speakers was found. However, the advantage of hearing subjects was removed in a visuo-spatial STM task. We attribute the source of the lower span to the internal structure of signs: indeed, unlike English (or Italian) words, signs contain both simultaneous and sequential components. Nonetheless, sign languages are fully-fledged grammatical systems, probably because the overall architecture of the grammar of signed languages reduces the STM load. Our hypothesis is that the faculty of language is dependent on STM, being however flexible enough to develop even in a relatively hostile environment.     

Sign language as cognition for deaf people: Pitfalls and prospects

With a tradition reliance on verbal paradigms cognitive psychology has repeatedly rediscovered the centrality of verbal processes in the cognitive representation of the world. Frequently it has been considered that non-speaking groups offer the proof of such psychological theories. Deaf people, because of their apparently poor memory, retardation in reading, relative lack of speech, yet cognitive viability, have offered an ideal test population for cognitive paradigs. Unfortunately deaf people turn out not to be a non linguistic control. We have now discovered sign language—a visual, spatial representation form used naturally by profoundly deaf people. This apparently offers the key the deaf people's cognition without speech. This paper describes some aspects of what we know of deaf people and their language, critically examines some of the evidence for sign representation in memory, and discusses the methodological problems to be faced by anyone searching for conclusive evidence on deaf people's working memory. Despite the attractiveness of ‘sings for words’ in cognition, this paper argues that the evidences is weak and signs may not be equated easily with words.     

Acquiring English as a second language via print: The task for deaf children

Only a minority of profoundly deaf children read at age-level. We contend this reflects cognitive and linguistic impediments from lack of exposure to a natural language in early childhood, as well as the inherent difficulty of learning English only through the written modality. Yet some deaf children do acquire English via print. The current paper describes a theoretical model of how children could, in principle, acquire a language via reading and writing. The model describes stages of learning which represent successive, conceptual insights necessary for second/foreign language learning via print. Our model highlights the logical difficulties present when one cannot practice a language outside of reading/writing, such as the necessity of translating to a first language, the need for explicit instruction, and difficulty that many deaf children experience in understanding figurative language. Our model explains why learning to read is often a protracted process for deaf children and why many fail to make progress after some initial success. Because language acquisition is thought to require social interaction, with meaning cued by extralinguistic context, the ability of some deaf individuals to acquire language through print represents an overlooked human achievement worthy of greater attention by cognitive scientists.     

Age constraints on first versus second language acquisition: evidence for linguistic plasticity and epigenesis

Does age constrain the outcome of all language acquisition equally regardless of whether the language is a first or second one? To test this hypothesis, the English grammatical abilities of deaf and hearing adults who either did or did not have linguistic experience (spoken or signed) during early childhood were investigated with two tasks, timed grammatical judgement and untimed sentence to picture matching. Findings showed that adults who acquired a language in early life performed at near-native levels on a second language regardless of whether they were hearing or deaf or whether the early language was spoken or signed. By contrast, deaf adults who experienced little or no accessible language in early life performed poorly. These results indicate that the onset of language acquisition in early human development dramatically alters the capacity to learn language throughout life, independent of the sensory-motor form of the early experience.     

Working Memory and Spoken Language Comprehension in Young Children

This study has two theoretical dimensions: (a) to explore which components of Baddeley's (1986) working memory model are associated with children's spoken language comprehension, and (b) to compare the extent to which measures of the components of this fractionated model and an index of a unitary model (listening span) are able to predict individual differences in spoken language comprehension. Correlational analyses revealed that within a group of 66 4– and 5-year-old children both listening span and phonological memory, but not visuospatial memory, were associated with vocabulary knowledge and spoken language comprehension. However, of the proposed measures of central executive function—dual task coordination, sustained attention, verbal fluency—only the latter was related to children's ability to understand spoken language. Hierarchical regression analyses indicated that variance in vocabulary knowledge was best explained by phonological memory skills, whereas individual differences in spoken language comprehension exhibited unique and independent associations with verbal fluency.     

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.     

Speed of word recognition and vocabulary knowledge in infancy predict cognitive and language outcomes in later childhood

The nature of predictive relations between early language and later cognitive function is a fundamental question in research on human cognition. In a longitudinal study assessing speed of language processing in infancy, Fernald, Perfors and Marchman (2006) found that reaction time at 25 months was strongly related to lexical and grammatical development over the second year. In this follow-up study, children originally tested as infants were assessed at 8 years on standardized tests of language, cognition, and working memory. Speed of spoken word recognition and vocabulary size at 25 months each accounted for unique variance in linguistic and cognitive skills at 8 years, effects that were attributable to strong relations between both infancy measures and working memory. These findings suggest that processing speed and early language skills are fundamental to intellectual functioning, and that language development is guided by learning and representational principles shared across cognitive and linguistic domains.     

Speech timing and working memory in profoundly deaf children after cochlear implantation

Thirty-seven profoundly deaf children between 8- and 9-years-old with cochlear implants and a comparison group of normal-hearing children were studied to measure speaking rates, digit spans, and speech timing during digit span recall. The deaf children displayed longer sentence durations and pauses during recall and shorter digit spans compared to the normal-hearing children. Articulation rates, measured from sentence durations, were strongly correlated with immediate memory span in both normal-hearing and deaf children, indicating that both slower subvocal rehearsal and scanning processes may be factors that contribute to the deaf children's shorter digit spans. These findings demonstrate that subvocal verbal rehearsal speed and memory scanning processes are not only dependent on chronological age as suggested in earlier research by. Instead, in this clinical population the absence of early auditory experience and phonological processing activities before implantation appears to produce measurable effects on the working memory processes that rely on verbal rehearsal and serial scanning of phonological information in short-term memory.     

Effects of Age on the Temporal Organization of Working Memory in Deaf Signers

ABSTRACT

Deaf native signers have a general working memory (WM) capacity similar to that of hearing non-signers but are less sensitive to the temporal order of stored items at retrieval. General WM capacity declines with age, but little is known of how cognitive aging affects WM function in deaf signers. We investigated WM function in elderly deaf signers (EDS) and an age-matched comparison group of hearing non-signers (EHN) using a paradigm designed to highlight differences in temporal and spatial processing of item and order information. EDS performed worse than EHN on both item and order recognition using a temporal style of presentation. Reanalysis together with earlier data showed that with the temporal style of presentation, order recognition performance for EDS was also lower than for young adult deaf signers. Older participants responded more slowly than younger participants. These findings suggest that apart from age-related slowing irrespective of sensory and language status, there is an age-related difference specific to deaf signers in the ability to retain order information in WM when temporal processing demands are high. This may be due to neural reorganisation arising from sign language use. Concurrent spatial information with the Mixed style of presentation resulted in enhanced order processing for all groups, suggesting that concurrent temporal and spatial cues may enhance learning for both deaf and hearing groups. These findings support and extend the WM model for Ease of Language Understanding.     

Space is special in Sign

Following groundbreaking work by linguists and cognitive scientists over the past thirty years, it is now generally accepted that sign languages of the deaf, such as ASL (American Sign Language) or BSL (British Sign Language), are structured and processed in a similar manner to spoken languages. The one striking difference is that they operate in a wholly non-auditory, visuospatial medium. How does the medium impact on language processing itself?     

Communication options for children with hearing loss

This article examines the communication options that are available for use within families of infants and young children who are hard-of-hearing or deaf. The need for language development, regardless of the specific communication mode, is stressed. The demands of the current environment of early identification and intervention often put families in a position of needing to decide among communication methods before they are fully knowledgeable and/or emotionally ready. Specific communication options are delineated and considered within a continuum of spoken and visual language. Available research related to early acquisition of language by infants and young children who are hard-of-hearing and deaf is reviewed; outcomes, when available, are presented for specific methods from reports of older children. Factors that influence families' decisions regarding the selection of a communication option are highlighted in the context of the existing literature. An ongoing evaluative process that respects the choices of families is advocated; a context in which change(s) in communication mode through childhood is viewed as a positive circumstance. The ultimate goal in the selection of any communication approach is to ensure that infants and young children who are hard of hearing or deaf and their families are language proficient and fluent communicators.     

Language Acquisition is Language Change

According to the theory of Universal Grammar, the primary linguistic data guides children through an innately specified space of hypotheses. On this view, similarities between child-English and adult-German are as unsurprising as similarities between cousins who have never met. By contrast, experience-based approaches to language acquisition contend that child language matches the input, with nonadult forms being simply less articulated versions of the forms produced by adults. This paper reports several studies that provide support for the theory of Universal grammar, and resist explanation on experience-based accounts. Two studies investigate English-speaking children’s productions, and a third examines the interpretation of sentences by Japanese speaking children. When considered against the input children are exposed to, the findings of these and other studies are consistent with the continuity hypothesis, which supposes that child language can differ from the language spoken by adults only in ways that adult languages can differ from each other.     

Deviant ERP response to spoken non-words among adolescents exposed to cocaine in utero

Concern for the impact of prenatal cocaine exposure (PCE) on human language development is based on observations of impaired performance on assessments of language skills in these children relative to non-exposed children. We investigated the effects of PCE on speech processing ability using event-related potentials (ERPs) among a sample of adolescents followed prospectively since birth. This study presents findings regarding cortical functioning in 107 prenatally cocaine-exposed (PCE) and 46 non-drug-exposed (NDE) 13-year-old adolescents.PCE and NDE groups differed in processing of auditorily presented non-words at very early sensory/phonemic processing components (N1/P2), in somewhat higher-level phonological processing components (N2), and in late high-level linguistic/memory components (P600).These findings suggest that children with PCE have atypical neural responses to spoken language stimuli during low-level phonological processing and at a later stage of processing of spoken stimuli.     

Working memory in multilingual children: Is there a bilingual effect?

This research investigates whether early childhood bilingualism affects working memory performance in 6- to 8-year-olds, followed over a longitudinal period of 3 years. The study tests the hypothesis that bilinguals might exhibit more efficient working memory abilities than monolinguals, potentially via the opportunity a bilingual environment provides to train cognitive control by combating interference and intrusions from the non-target language. A total of 44 bilingual and monolingual children, matched on age, sex, and socioeconomic status, completed assessments of working memory (simple span and complex span tasks), fluid intelligence, and language (vocabulary and syntax). The data showed that the monolinguals performed significantly better on the language measures across the years, whereas no language group effect emerged on the working memory and fluid intelligence tasks after verbal abilities were considered. The study suggests that the need to manage several language systems in the bilingual mind has an impact on children's language skills while having little effects on the development of working memory.     

Language access and theory of mind reasoning: evidence from deaf children in bilingual and oralist environments

This investigation examined whether access to sign language as a medium for instruction influences theory of mind (ToM) reasoning in deaf children with similar home language environments. Experiment 1 involved 97 deaf Italian children ages 4-12 years: 56 were from deaf families and had LIS (Italian Sign Language) as their native language, and 41 had acquired LIS as late signers following contact with signers outside their hearing families. Children receiving bimodal/bilingual instruction in LIS together with Sign-Supported and spoken Italian significantly outperformed children in oralist schools in which communication was in Italian and often relied on lipreading. Experiment 2 involved 61 deaf children in Estonia and Sweden ages 6-16 years. On a wide variety of ToM tasks, bilingually instructed native signers in Estonian Sign Language and spoken Estonian succeeded at a level similar to age-matched hearing children. They outperformed bilingually instructed late signers and native signers attending oralist schools. Particularly for native signers, access to sign language in a bilingual environment may facilitate conversational exchanges that promote the expression of ToM by enabling children to monitor others' mental states effectively.     

How children make language out of gesture: morphological structure in gesture systems developed by American and Chinese deaf children

When children learn language, they apply their language-learning skills to the linguistic input they receive. But what happens if children are not exposed to input from a conventional language? Do they engage their language-learning skills nonetheless, applying them to whatever unconventional input they have? We address this question by examining gesture systems created by four American and four Chinese deaf children. The children's profound hearing losses prevented them from learning spoken language, and their hearing parents had not exposed them to sign language. Nevertheless, the children in both cultures invented gesture systems that were structured at the morphological/word level. Interestingly, the differences between the children's systems were no bigger across cultures than within cultures. The children's morphemes could not be traced to their hearing mothers' gestures; however, they were built out of forms and meanings shared with their mothers. The findings suggest that children construct morphological structure out of the input that is handed to them, even if that input is not linguistic in form.