This study tests the hypothesis that developmental dyslexia is (partly) caused by a deficit in implicit sequential learning, by investigating whether infants at familial risk of dyslexia can track non-adjacent dependencies in an artificial language. An implicit learning deficit would hinder detection of such dependencies, which mark grammatical relations (e.g. between ‘is’ and ‘-ing’ in ‘she is happily singing’). In a head-turn experiment with infants aged 1;6, family risk and typically developing infants were exposed to one of two novel languages containing dependencies of the type a-X-c, b-X-d or a-X-d, b-X-c, with fixed first and third elements and twenty-four different X elements. During test, typically developing children listened longer to ungrammatical strings (i.e. that did not correspond to their training language). However, family-risk children did not discriminate between grammatical and ungrammatical strings, indicating deficient implicit learning. The implications of these findings in relation to dyslexia and other language-based disorders are discussed.

Children's assignment of novel words to nameless objects, over objects whose names they know (mutual exclusivity; ME) has been described as a driving force for vocabulary acquisition. Despite their ability to use ME to fast-map words (Preissler & Carey, 2005), children with autism show impaired language acquisition. We aimed to address this puzzle by building on studies showing that correct referent selection using ME does not lead to word learning unless ostensive feedback is provided on the child's object choice (Horst & Samuelson, 2008). We found that although toddlers aged 2;0 at risk for autism can use ME to choose the correct referent of a word, they do not benefit from feedback for long-term retention of the word–object mapping. Further, their difficulty using feedback is associated with their smaller receptive vocabularies. We propose that difficulties learning from social feedback, not lexical principles, limits vocabulary building during development in children at risk for autism.

For sixty-seven children with ASD (age 1;6 to 5;11), mean Total Vocabulary score on the Language Development Survey (LDS) was 65·3 words; twenty-two children had no reported words; and twenty-one children had 1–49 words. When matched for vocabulary size, children with ASD and children in the LDS normative sample did not differ in semantic category or word-class scores. Q correlations were large when percentage use scores for the ASD sample were compared with those for samples of typically developing children as well as children with vocabularies <50 words. The 57 words with the highest percentage use scores for the ASD children were primarily nouns, represented a variety of semantic categories, and overlapped substantially with the words having highest percentage use scores in samples of typically developing children as well as children with lexicons of <50 words. Results indicated that the children with ASD were acquiring essentially the same words as typically developing children, suggesting delayed but not deviant lexical composition.

Children with pre/perinatal unilateral brain lesions (PL) show remarkable plasticity for language development. Is this plasticity characterized by the same developmental trajectory that characterizes typically developing (TD) children, with gesture leading the way into speech? We explored this question, comparing eleven children with PL – matched to thirty TD children on expressive vocabulary – in the second year of life. Children with PL showed similarities to TD children for simple but not complex sentence types. Children with PL produced simple sentences across gesture and speech several months before producing them entirely in speech, exhibiting parallel delays in both gesture + speech and speech-alone. However, unlike TD children, children with PL produced complex sentence types first in speech-alone. Overall, the gesture–speech system appears to be a robust feature of language learning for simple – but not complex – sentence constructions, acting as a harbinger of change in language development even when that language is developing in an injured brain.

This is a naturalistic study of the development of language in Hebrew-speaking children with Williams syndrome (WS) and children with Down syndrome (DS), whose MLU extended from 1·0 to 4·4. Developmental curves over the entire span of data collection revealed minor differences between children with WS, children with DS, and typically developing (TD) controls of similar MLU. Development within one calendar year showed remarkable synchrony among the variables. However, age of language onset and pace of acquisition departed significantly from normal timing. It is argued that in view of the centrality of genetic timing and the network properties of cognition, normal schedules are crucial determinants of intact development. Consequently, with respect to neurodevelopmental syndromes, the so-called ‘language delay’ is indicative of deviance that is likely to impact development in critical ways.

This study examined the production of three types of noun plural inflections, feminine sound plural (FSP), masculine sound plural (MSP), and broken plural (BP) in Kuwaiti Arabic-speaking children with and without language impairment. A total of thirty-six Kuwaiti participants – twelve adults, twelve children with specific language impairment (SLI), and twelve typically developing age-matched controls (TD) were presented with twenty-seven pictured stimuli of real and nonsense words. The results showed that the TD children were significantly more accurate in using the required noun plural inflections than the SLI group. The TD children's preferred overgeneralization strategy was to substitute FSP for the regular MSP and irregular BP contexts much more than their peers with SLI. The performance of the SLI group also differed from that of their age-matched counterparts in the number of errors and their distribution across categories. The results are discussed in the light of relevant theories of atypical language development.

Previous research has shown that high phonotactic frequencies facilitate the production of regularly inflected verbs in English-learning children with specific language impairment (SLI) but not with typical development (TD). We asked whether this finding can be replicated for German, a language with a much more complex inflectional verb paradigm than English. Using an elicitation task, the production of inflected nonce verb forms (3rd person singular with -t suffix) with either high- or low-frequency subsyllables was tested in sixteen German-learning children with SLI (ages 4;1–5;1), sixteen TD-children matched for chronological age (CA) and fourteen TD-children matched for verbal age (VA) (ages 3;0–3;11). The findings revealed that children with SLI, but not CA- or VA-children, showed differential performance between the two types of verbs, producing more inflectional errors when the verb forms resulted in low-frequency subsyllables than when they resulted in high-frequency subsyllables, replicating the results from English-learning children.

We adapted the semantic fluency task into British Sign Language (BSL). In Study 1, we present data from twenty-two deaf signers aged four to fifteen. We show that the same ‘cognitive signatures’ that characterize this task in spoken languages are also present in deaf children, for example, the semantic clustering of responses. In Study 2, we present data from thirteen deaf children with Specific Language Impairment (SLI) in BSL, in comparison to a subset of children from Study 1 matched for age and BSL exposure. The two groups' results were comparable in most respects. However, the group with SLI made occasional word-finding errors and gave fewer responses in the first 15 seconds. We conclude that deaf children with SLI do not differ from their controls in terms of the semantic organization of the BSL lexicon, but that they access signs less efficiently.

Children with Down syndrome typically have weaknesses in oral language, but it has been suggested that this domain may benefit from learning to read. Amongst oral language skills, vocabulary is a relative strength, although there is some evidence of difficulties in learning the phonological form of spoken words. This study investigated the effect of orthographic support on spoken word learning with seventeen children with Down syndrome aged seven to sixteen years and twenty-seven typically developing children aged five to seven years matched for reading ability. Ten spoken nonwords were paired with novel pictures; for half the nonwords the written form was also present. The spoken word learning of both groups did not differ and benefited to the same extent from the presence of the written word. This suggests that compared to reading-matched typically developing children, children with Down syndrome are not specifically impaired in phonological learning and benefit equally from orthographic support.

This study compared the receptive and expressive language profiles of verbally expressive children and adolescents with Down Syndrome (DS) and those with Fragile X syndrome (FXS) and examined the extent to which these profiles reliably differentiate the diagnostic groups. A total of twenty-four verbal participants with DS (mean age: 12 years), twenty-two verbal participants with FXS (mean age: 12 years), and twenty-seven participants with typical development (TD; mean age = 4 years) completed standardized measures of receptive and expressive vocabulary and grammar, as well as a conversational language sample. Study results indicate that there are distinct DS and FXS language profiles, which are characterized by differences in grammatical ability. The diagnostic groups were not differentiated based on vocabulary performance. This study supports the existence of unique language profiles associated with DS and FXS.

Research on language in individuals with Williams syndrome (WS) has been fueled by persistent theoretical controversies for two decades. These shifted from initial focus on dissociations between language and cognition functions, to examining the paradox of socio-communicative impairments despite high sociability and relatively proficient expressive language. We investigated possible sources of communicative difficulties in WS in a collaborative referential communication game. Five- to thirteen-year-old children with WS were compared to verbal mental age- and to chronological age-matched typically developing children in their ability to consider different types of information to select a speaker's intended referent from an array of items. Significant group differences in attention deployment to object locations, and in the number and types of clarification requests, indicated the use of less efficient and less mature strategies for reference resolution in WS than expected based on mental age, despite learning effects similar to those of the comparison groups, shown as the game progressed.