RUNNING HEAD : Vocabulary learning in Down syndrome The benefit of orthographic support for oral vocabulary learning in children with Down syndrome

Publication Summary

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 17 children with Down syndrome aged 7-16 years and 27 typically developing children aged 5-7 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 benefitted 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. Vocabulary learning in Down syndrome 3 THE BENEFIT OF ORTHOGRAPHIC SUPPORT FOR ORAL VOCABULARY LEARNING IN CHILDREN WITH DOWN SYNDROME Down syndrome is most commonly caused by an extra copy of chromosome 21 (Trisomy 21) and has a prevalence rate of 1.08 in every 1000 live births (Morris & Alberman, 2009). Down syndrome results in a learning disorder, that can range from mild to severe but is generally associated with an IQ of approximately 50 (Chapman & Hesketh, 2000; Määttä, Tervo-Määttä, Taanila, Kaski, & Livanainen, 2006). Children with Down syndrome typically show relative strengths in social skills, word reading and visual short-term memory (Boudreau, 2002; Buckley, 1995; Fidler, Hepburn, & Rogers, 2006; Jarrold, Baddeley, & Hewes, 1999) and relative weaknesses in oral language and verbal short-term memory (Abbeduto, Warren, & Conners, 2007; Jarrold et al., 1999). Within literacy skills, individuals with Down syndrome have difficulties in nonword reading and reading comprehension in comparison to their strength in word reading (Nash & Heath, 2011; Roch & Jarrold, 2008) Within the oral language domain, expressive language tends to be weaker than receptive language (Laws & Bishop, 2003), and expressive vocabulary has been found to be below the level expected given nonverbal ability (Næss et al., 2011). Buckley (1995) suggested that the relatively intact word reading skills of children with DS may serve to promote their oral language development. So far, however, experimental evidence for this suggestion is lacking. There is also an outstanding question concerning different aspects of vocabulary learning in individuals with Down syndrome. Vocabulary knowledge incorporates both phonological and semantic knowledge and there is some evidence that it is the learning of the phonological form that is particularly impaired in Down syndrome (Jarrold, Thorn, & Stephens, 2009 c.f. Mosse & Jarrold, 2011). The present study investigated vocabulary learning in children with Down syndrome and, more specifically, the extent to which phonological learning can be aided by orthographic support from a written word. Vocabulary learning in Down syndrome 4 The fast-mapping paradigm has been used with individuals with Down syndrome to investigate vocabulary learning. Fast-mapping is a form of incidental learning where a label for a novel object is introduced in the context of another task, often a game (Carey & Bartlett, 1978). The first of these studies (Chapman, Kay-Raining Bird, & Schwartz, 1990) found that children with Down syndrome, who had a mean age of 12;06, comprehended and produced new words as well as typically developing children, who had a mean age of 4;01. The two groups were explicitly matched for nonverbal ability and also performed similarly on receptive and expressive vocabulary tasks. Chapman et al.’s findings have been replicated (Kay-Raining Bird, Chapman, & Schwartz, 2004) but advantages for typically developing children have been found earlier in development or when matched for receptive syntax, which is a weakness compared to nonverbal ability for children with Down syndrome (Kay-Raining Bird, Gaskell, Dallaire, & MacDonald, 2000; McDuffie, Sindberg, Hesketh, & Chapman, 2007). Therefore the results of these studies appear to depend on the characteristics of the comparison group. In their fast-mapping study, Chapman et al. (1990) also administered a recognition task which required children to choose between the target name (koob) and two distracters, one which had the same rime unit as the target (soob) and one which had a stop consonant as the initial phoneme like the target (tid). This task was only administered to children who did not correctly produce the target name, i.e. those children with poor learning. This was evidenced by pass rates varying between 29% and 58% across groups and on immediate and delayed post-tests. When children chose an incorrect answer, it tended to be the distracter with the phonetically similar initial phoneme to the target, which the authors argued suggests children had some phonological knowledge about the onset of the word, but not the rime. The production tasks used in the fast-mapping studies above used lenient criteria to determine what was accepted as a correct answer; a response was still considered correct if there was an error on one phoneme in the target word, or if a phoneme was added. Therefore, with the exception of Chapman et al.’s (1990) recognition task which was only administered to a small Vocabulary learning in Down syndrome 5 number of children, these tasks could be successfully completed even if the child had a relatively poor phonological representation of the novel word. Problems with articulation are common in children with Down syndrome (Kumin, Councill, & Goodman, 1994; Roberts et al., 2005), thus making it difficult to assess production of new words. To circumvent this whilst stringently assessing the quality of the phonological representation, Jarrold et al. (2009) tested phonological learning using a receptive multiple choice task rather than a production task. This required children to choose the word they had learnt and ignore two distracters which were phonetically similar to the target nonword. Individuals with Down syndrome aged 14-29 years and typically developing children aged 5-8 years took part. The individuals with Down syndrome were found to be impaired on this task compared to typically developing children matched for nonverbal ability, receptive vocabulary and expressive vocabulary. Mosse and Jarrold (2011) extended this work using a similar training methodology but requiring a spoken response in a series of three experiments with individuals with Down syndrome aged 9-30 years and typically developing children aged 4-6 years. In contrast to Jarrold et al. (2009), there were no differences in phonological learning between the two groups of children. This finding remained when the same receptive multiple choice task as Jarrold et al. was used as the outcome measure. It was argued that this conflicting result may be because the target item appeared more frequently than the distracters in the original study, and the typically developing children benefitted more from this. In summary, it is currently unclear as to whether children with Down syndrome have difficulties learning the phonological forms of words relative to their general developmental level. As children with Down syndrome have oral language and verbal short-term memory difficulties, the use of visual support has often been encouraged in their education particularly in language instruction. Buckley (1995) proposed that seeing orthography, or the written form of words, helps the oral language development of children with Down syndrome. There are, at least, two ways in which seeing the written form of a word may help children learn its spoken form. Vocabulary learning in Down syndrome 6 Buckley argued that ‘reading practice improves phonology and articulation, possibly because the letters in words provide the cues the child needs to sound all the phonemes’ (p. 161). If children can identify the individual phonemes in a new spoken word then this may result in their phonological output, and therefore representation, being more accurate. Additionally the orthography may provide children with another representation of the new word form, which strengthens the overall representation in the lexicon and therefore aids retrieval at a later date (Perfetti & Hart, 2002). Some case studies suggest that teaching young children with Down syndrome to read promotes oral language development, particularly in the production of words or sentences which are first introduced in their written form (de Graaf, 1993; Duffen, 1976). In a longitudinal study with a group of 14 children with Down syndrome, Laws, Buckley, Bird, MacDonald and Broadley (1995) found that those who could read made more progress on oral language measures than those who could not read. However the group of children who could read had more advanced oral language skills at the first time point. Furthermore, all the children who could not read were in special education and those who could read were mostly in mainstream education, which has been found to lead to greater progress in oral language (Buckley, Bird, Sacks, & Archer, 2006). In a different longitudinal study with individuals with Down syndrome, Laws and Gunn (2002) found that initial reading skills correlated with mean length of utterance five years later, but not receptive language. Therefore there is some evidence to suggest a positive relationship between reading and oral language. If reading does promote oral language development, as suggested by evidence from case studies, we need to determine whether this is a special or unique relationship or whether it reflects what we see in typically developing children of the same mental age or reading ability. Studies with typically developing children aged 7 to 11 years hav