Individuals with Down syndrome have difficulty with phonological awareness tasks in relation to their chronological age, nonverbal ability and reading accuracy. This, despite Cossu et al.’s (1993) claims, does not mean that phonological awareness skills are not relevant to how children with Down syndrome learn to read. Numerous studies have examined the relationship between phonological awareness and reading accuracy in Down syndrome and these will now be reviewed.
Cardoso-Martins and Frith (2001) categorised the individuals with Down syndrome participating in their study as readers or non-readers. There were 46 readers and 47 non- readers; readers were defined as those scoring four or above on a single word reading task. The readers performed significantly better on tasks of initial phoneme detection, letter knowledge, nonverbal cognition and were also younger. The difference in initial phoneme detection was still significant after controlling for age, letter knowledge and nonverbal ability. In their sample of children with Down syndrome Fowler et al. (1995) found that no individual with decoding skills above the level of a 6-7 year old typically developing child scored below chance on a test of phoneme deletion, and although some individuals scored well on phoneme deletion but poorly on decoding, the reverse was not true. Similarly Kennedy and Flynn (2003) found that only three out of their sample of nine children with Down syndrome scored above
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zero on a nonword reading task, and these were the children who had the highest phonological awareness scores. These studies suggest that phonological awareness skills may be necessary, but not sufficient, for good word and nonword reading for individuals with Down syndrome. However, cut-off scores or median splits of groups result in low statistical power and can lead to children of similar abilities being in separate groups, and it is therefore more informative to investigate correlations between reading skills and phonological awareness.
Roch and Jarrold (2008) compared the relationship between nonword reading and a composite phonological awareness measure of alliteration detection and phoneme deletion in a group of individuals with Down syndrome and a typically developing control group matched on regular word reading. In both groups there was a similar relationship between nonword reading and phonological awareness, which would suggest that individuals with Down syndrome utilise phonological awareness to the same extent as typically developing children whilst decoding. Fletcher and Buckley (2002) found significant correlations between reading accuracy and phonological awareness in a group of 17 individuals with Down syndrome; more specifically, when age and verbal short-term memory were controlled, rime detection and phoneme segmentation correlated with reading accuracy. The participants in both these studies were reading at approximately the level of a seven year old typically developing child. These were, therefore, relatively high-achieving children, and as such the results from these studies may not necessarily generalise to all individuals with Down syndrome.
There are various aspects of phonological awareness and individuals with Down syndrome do not perform equivalently on measures of these different skills. Gombert (2002) examined the relationship between different phonological awareness tasks and reading accuracy in a group of 11 individuals with Down syndrome aged 10-20 years and a group of 11 typically developing children aged 6-8 years matched on reading accuracy. Phoneme counting and phoneme deletion correlated with reading accuracy to a similar extent in the children with Down syndrome and the typically developing children. However, whereas an alliteration oddity task was moderately correlated with reading accuracy in the individuals with Down syndrome, it was negligibly correlated with reading accuracy in the typically developing group. Kennedy and Flynn (2003) also found that alliteration matching was significantly correlated with reading accuracy for participants with Down syndrome, however rime detection, phoneme isolation
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and phoneme blending were not. Fowler et al. (1995) examined the correlation between phoneme deletion, a relatively complex task of phoneme awareness, reading accuracy and nonword reading; phoneme deletion accounted for 36% of variance in a reading accuracy task and 49% of the variance in a nonword reading task. Therefore phonological awareness is related to reading accuracy in individuals with Down syndrome, and tasks involving the initial sounds of words may be particularly important. However methodological concerns mean that these findings must be treated as preliminary. Kennedy and Flynn provide the raw scores for each of their participants and many of the children did not score above chance on any of the tasks and many of the children scored zero on the phoneme isolation task. Neither Kennedy and Flynn nor Fowler et al. included a control group and both Kennedy and Flynn’s and Gombert’s study used limited sample sizes, eleven and nine respectively.
Boudreau (2002) included a larger sample of children with Down syndrome along with a typically developing control group matched on nonverbal ability and found that in contrast to Kennedy and Flynn (2003), blending was significantly correlated with reading accuracy for the children with Down syndrome, whereas for the typically developing children alliteration oddity was significantly correlated with reading accuracy. No phonological awareness measure correlated with decoding in the individuals with Down syndrome, whereas blending was significantly correlated with decoding in the typically developing group. However decoding was at floor in both groups, and therefore correlations involving this task must be interpreted with caution. Snowling et al. (2002) included a control group matched on reading accuracy meaning that any differences in correlations cannot be due to the different reading levels of the two groups of children. Similar correlations were found between a measure of phoneme detection, which included initial and final phonemes, and reading accuracy in individuals with Down syndrome and the typically developing children.
Letter-sound knowledge is important for acquiring the alphabetic principle that in turn is important for learning to read, more specifically to decode. Kennedy and Flynn (2003) found that the correlation between letter-sound knowledge and reading accuracy was strong for individuals with Down syndrome, and the relationship between letter-name knowledge and reading accuracy was moderate. However this was with a small sample and two other studies with larger groups of children suggest that the relationship between letter-sound knowledge
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and reading accuracy may not be significant. Snowling et al. (2002) found that letter-name but not letter-sound knowledge was correlated with reading accuracy for individuals with Down syndrome, whereas for typically developing children letter-sound knowledge was strongly correlated with reading accuracy. Boudreau (2002) also found that for children with Down syndrome, letter-name knowledge was significantly correlated with reading accuracy, whereas for the typically developing group, both letter-name and letter-sound knowledge were
significantly correlated with reading accuracy. In both these studies, the groups of children with Down syndrome had similar levels of letter-sound knowledge to their control groups, but the lack of a relationship with reading accuracy suggests that they have difficulty applying this knowledge to reading. Conversely, letter-name knowledge was related to reading accuracy in both studies; Snowling et al. (2002) suggests that this relationship may occur not because of a reason associated with the alphabetic principle but rather because both skills involve learning associations between visual referents and their names.
1.5.1.3. Relationship between reading accuracy and broader oral language skills.