and Melhorn (2005), in which it is suggested that prosodic cues are the lowest weighted cues in adult speech segmentation and the most critical ones at the onset of language development (lower than segmental and lexical cues). It appears that individuals with WS seem to be “stuck” in the lowest part of the hierarchy where they need prosodic cues in order to be able to make reliable acceptability judgments. And because of their strong preference for local processing, they need the prosodic cues to help them decide which sequences are acceptable. This suggests a possibly atypical processing strategy in WS.
There have been fewer studies of infants and toddlers with WS compared with ones on children, adolescents and adults, and although informative, the evidence is inconclusive. There is evidence for an asynchronous relationship between language and other cognitive abilities due to poorer language than cognitive abilities (Stojanovik & James, 2006), but also due to stronger language than cognitive abilities (Mervis & Bertrand, 1997). It is generally agreed, though, that the onset of language acquisition in WS in the early stages is delayed (Paterson, Girelli, Gsodl, Johnson, & Karmiloff‐Smith, 1999; Semel & Rosner, 2003; Stojanovik & James, 2006). The median age at which infants with WS have a vocabulary of 10 expressive words is 28 months, compared with 13.5 months in neurotypical infants (Mervis, Robinson, Rowe, Becerra, & Klein‐Tasman, 2003). Based on longitudinal data from Hebrew‐speaking children with WS, Levy and Eilam (2013) reported that infants with WS started to use combinatorial language on average 24 months later than their typically developing peers.
The reasons for the early language delay are still unknown. A recent study of statistical learning of young infants with WS aged between 8 and 20 months showed that they were able to discriminate between statistically defined “words” and “part words” in an AGL paradigm (Cashon, Ha, Estes, Saffran, & Mervis, 2016). This shows that infants with WS were able to detect statistical regularities in the speech stream, which suggests that the delayed early lexical acquisition of infants with WS may not be the result of their inability to segment words from the speech stream.
Early language acquisition in WS is generally an under‐researched area, and more longitudinal studies are needed in order to find out how language is acquired in WS and the relationship between language and other cognitive abilities.
Despite a large body of research into the morpho‐syntactic abilities of people with WS, there have been fewer studies investigating actual communication or pragmatic skills in this population. There have been reports that good social communication skills are a “hallmark” of the syndrome (Jones et al., 2000). Mervis, Klein‐Tasman, and Mastin (2001), using the Vineland Adaptive Behaviour Scales (VABS; Sparrow, Balla, & Cichetti, 1984), reported that communication in WS is a relative strength. In particular, Jones et al. (2000) argued that superior social‐communication skills distinguish this population from populations with other developmental disorders, such as DS and autism. In a series of tasks, Jones et al. (2000) reported that children with WS include a higher number of inferences about the affective state and motivation of story characters in comparison to typically developing children and children with DS. In the same study, individuals with WS provided a greater number of descriptions of affective states and evaluative comments during an interview task, and were more likely to ask questions of the interviewer. This was interpreted as showing that individuals with WS are “hypersocial.”
There have also been clinical and parental reports, as well as a number of research studies, that have shown that individuals with WS have problems in establishing friendships and have social difficulties, such as disinhibition and social isolation (Davies, Udwin, & Howlin, 1998).
Some studies have shown that individuals with WS are not sensitive to the needs of the conversational partner (Udwin & Yule, 1991). Further to this, Stojanovik et al. (2001) reported a high level of conversational inadequacy in a pilot study of a group of children with WS, in which participants with WS were found to have a tendency not to provide enough information for the conversational partner. Laws and Bishop (2004) reported pragmatic language impairment and social deficits in a group of older children and young adults with WS, using the Children’s Communication Checklist (Bishop, 1998). The checklist ratings showed pragmatic language deficits, evident from inappropriate initiations of conversation, and use of stereotyped conversation. Furthermore, Stojanovik (2006) reported that children with WS have difficulties with exchange structure and responding appropriately to the interlocutor’s requests for information and clarification. They also had significant difficulties with interpreting meaning and providing enough information for the conversational partner. A later, longitudinal study by John, Dobson, Thomas, and Mervis (2012) reported similar findings, in that they found a relationship between children’s pragmatic ability at 9–12 years of age and their earlier secondary subjectivity (i.e., the ability to produce utterances which are paired with eye‐contact).
Lacroix, Bernicot, and Reilly (2007) investigated the abilities of children with WS to interact for the purpose of attaining a goal. The task required the mother and the child to collaborate and negotiate in order to produce a drawing on the computer, on the basis of a drawing model. During this collaborative conversation task, the children and adolescents with WS (similarly to those with DS) produced fewer utterances than the typically developing participants and played a weak role in the conversation compared to their mother. However, they readily expressed their psychological states (like younger children of the same nonverbal mental age). Also, the children and adolescents with WS responded to maternal directives less often than all other groups.
Children with WS also find it difficult to verbalize message inadequacy (John, Rowe, & Mervis, 2009). Using a barrier, listener‐role referential communication task, the child was instructed to follow the researcher’s instructions. The children performed well when the instructions were adequate, but found it considerably more difficult when the instructions were inadequate, that is, when the instructions were ambiguous, or the instruction contained vocabulary the child did not understand, in that they indicated less than half of the time that there was a problem. When they verbalized that there was a problem, the verbalizations were often too vague for the researcher to identify a problem, or they identified the wrong problem. The ability to verbalize message inadequacy was related to the children’s chronological age and theory of mind.
Narrative skills in individuals with WS seem to be poorer than those of mental age‐matched neurotypical controls. For example, despite relative strengths in phonological, lexical, and syntactic abilities, individuals with WS had difficulties with discourse planning and organization, and produced less coherent narratives (Marini, Martelli, Gagliardi, Fabbro, & Borgatti, 2010). This finding is in line with earlier studies which suggested difficulties with pragmatics and discourse processing in individuals with WS (Laws & Bishop, 2004). Poor quality of narrative production in terms of structural coherence and process complexity (compared to chronological age‐matched controls) was also reported in a study by Gonçalves et al. (2010).
In summary, although it is evident that research on WS has moved substantially from the initial claims that individuals with WS have “intact” language abilities despite severe cognitive deficits, the emerging picture is much less clear and the question of the contribution of atypical populations, such as individuals with WS to which constraints guide typical language acquisition, is more open to debate than ever before. The evidence base is growing, however. in the direction of highlighting possible atypical developmental pathways and relative strengths and weaknesses.
5.3 Language and Communication in Down Syndrome (DS)
DS is a genetic disorder caused by a partial or complete duplication of chromosome 21 (Epstein, 1986). It affects approximately 1 in 691 live births (Parker et al., 2010). DS is the most common cause of intellectual disability and seems to be particularly detrimental to language acquisition. A lot can be learnt about language in individuals with DS by reading reports on individuals with WS because people with DS are often included as a comparison group in studies of individuals with WS—individuals with WS and those with DS have similar nonverbal abilities but often different language profiles (Bellugi, Linchtenberger, Lai, & St.George, 2000; Bellugi et al., 1994; Jarrold et al., 1998; Reilly, Klima, & Bellugi, 1990).
As in individuals