Language and phonological skills in children
at high risk of reading di⁄culties
Julia M. Carroll and Margaret J. Snowling
...
speech impairments relates to the nature of their
phonological impairments. An integrating theory is
that reading difficult...
Taylor, 1998) and children at high risk of dyslexia
show poor letter knowledge at school entry (Scar-
borough, 1990). To l...
Phonological processing. Mispronunciation detection
(input phonology): In this task, the children were intro-
duced to a p...
chosen the wrong alternative, they were told ÔNo, button
and butter have the same sound, ÔbutÕ, at the beginning.
Sandwich...
that the subjects were individually matched, it was
not appropriate to use standard 2 · 2 Chi-square
analyses, and the dat...
were matched with controls in consolidated voca-
bulary knowledge on the picture vocabulary test.
Although our data do not...
difficulty in discriminating between accurate pro-
nunciations of familiar words and pronunciations
that are minimally dist...
know and what we don’t know. In B. Blachman (Ed.),
Foundations of reading acquisition and dyslexia:
Implications for early...
children: Causes, characteristics, intervention and
outcome (pp. 245–259). Hove, East Sussex: Psychol-
ogy Press.
Snowling...
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  1. 1. Language and phonological skills in children at high risk of reading di⁄culties Julia M. Carroll and Margaret J. Snowling University of York, UK Background: Dyslexia is now generally acknowledged to involve difficulties in phonological processing. However, the links between reading difficulties and speech difficulties remain unclear. Method: In the present study, 17 children with speech difficulties between the ages of four and six were compared to children with a family history of dyslexia and normally developing controls on phonological processing, phonological learning, phonological awareness and literacy tasks. Results: The two groups of children at risk of reading difficulties showed very similar patterns of impairment, with average vocabulary but poor input and output speech processing, phonological learning, phonological awareness and reading development. Conclusions: It is concluded that the antecedents of reading difficulty are similar in these two groups of children, with both groups showing deficits in the development of phonological representations. Keywords: Diagnosis, dyslexia, high risk studies, learning, phonological processing. It is widely accepted that learning to read depends on phonological skills and the corollary of this is that children who have phonological difficulties are at risk of reading problems. The group of children whose phonological deficits have attracted most re- search attention are those with dyslexia; these chil- dren’s deficits encompass problems of phonological awareness, verbal short-term memory and rapid automatised naming (Snowling, 2000a). Another group of children who are vulnerable to reading dif- ficulties are children with problems of expressive phonology. These children have phonological impairments that can be observed in speech output processes (Dodd, 1995; Stackhouse & Snowling, 1992). The extent to which their reading problems can be traced to deficits in phonological skills, rather than to broader language impairments that fre- quently accompany these, is not yet fully under- stood. Bishop and Adams (1990) followed the progress of a group of children who had had pre-school speech and language impairments at the age of 8 years. The literacy skills of those who had had isolated phono- logical impairments affecting expressive phonology were significantly better than those of children with language difficulties. Similar results were reported by Catts (1991) who found that children assessed in kindergarten as having speech impairments in the absence of language problems showed comparable reading levels to controls one year later in first grade. In contrast, children with speech and additional language impairments showed significantly worse performance. Similar findings were reported by Levi, Capozzi, Fabrizi, and Sechi (1982) and Nathan, Stackhouse, Goulandris, and Snowling (in press). Both of these studies compared the reading skills of speech-impaired children with and without addi- tional language problems. While both groups were delayed in literacy development, the children with additional language difficulties were more signific- antly impaired. These studies therefore suggest it is language, rather than speech, difficulties that are the main precursors of reading problems. However, it should be noted that the children classified as Ôspeech and language impairedÕ in these studies were more severely impaired in their speech as well as their language than the speech-only impaired group. It is therefore difficult to disentangle the effects of poor speech from those of poor language. Bird, Bishop, and Freeman (1995) conducted a study of speech-impaired children that avoided this methodological difficulty by comparing subgroups of children with and without language impairment that had equivalent levels of speech difficulty at the beginning of the study when they were aged five to six years old. When these children were followed up one and two years later, they showed deficits relative to controls matched for non-verbal IQ in reading, spelling and phonological awareness. These deficits were irrespective of whether children had additional language difficulties. The close similarity between the reading and phonological awareness difficulties observed among children with dyslexia and those with speech diffi- culties is such that it has been suggested that the two disorders lie on a continuum (Stackhouse & Wells, 1997; Snowling, 2000b) that has phonological processing difficulties at its core (cf. Stanovich & Siegal, 1994). In similar vein, Bishop and Adams (1990) proposed the Ôcritical age hypothesisÕ, which states that the extent to which a child is vulnerable to reading failure depends upon the status of their phonological processing skills at the stage when these are required for learning to read. A second issue that is not yet resolved regarding the risk of reading difficulties among children with Journal of Child Psychology and Psychiatry 45:3 (2004), pp 631–640 Ó Association for Child Psychology and Psychiatry, 2004. Published by Blackwell Publishing, 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main Street, Malden, MA 02148, USA
  2. 2. speech impairments relates to the nature of their phonological impairments. An integrating theory is that reading difficulties can be traced to poorly spe- cified phonological representations (Fowler, 1991; Metsala, 1997; Ramus, 2001; Swan & Goswami, 1997; Snowling & Hulme, 1994; Snowling, Bishop, & Stothard, 2000). However, this hypothesis leaves open the question of the extent of involvement of speech input (perception) and speech output (pro- duction) processes. Studies that have examined speech perception and spoken word identification in dyslexic readers have produced equivocal findings (Brady, 1997; Griffiths & Snowling, 2001; McBride- Chang, 1996; Metsala, 1997; Pennington & Lefly, 2001). Joanisse, Manis, Keating, and Seidenberg (2000) have suggested that variability in speech perception in dyslexia is associated with individual differences in oral language skill. Thus, perceptual problems appear to be more common among children with dyslexia who have concomitant language impair- ments. Studies that have examined the speech production abilities of children with dyslexia are comparatively rare (cf. Snowling, Hulme, Wells, & Goulandris, 1992). However, evidence from prospective studies of dyslexia among children from families at genetic risk of the disorder suggests that such difficulties are apparent during the pre-school years (Scarborough, 1990). Furthermore, school-age children with dys- lexia have difficulties on nonword repetition tasks that tap output phonological processes (Snowling, 1981; Snowling, Goulandris, Bowlby, & Howell, 1986). Indeed, Kamhi and Catts (1986) reported that performance on a test requiring the repetition of multisyllabic nonwords was as poor for reading- impaired children as for children with primary oral language impairments. Adding to the evidence implicating speech production deficits in reading failure, Leitao, Hogben, and Fletcher (1997) showed that speech-impaired children who showed a pattern of ÔdeviantÕ speech errors were poorer on tests of phonological awareness than speech-impaired chil- dren whose phonological errors could be described as delayed, i.e., like those of younger children. In short, there is reason to believe that there are continuities between oral and written language dif- ficulties. However, the hypothesis that developmen- tal speech difficulties presage dyslexia is simplistic. It seems that the risk of dyslexia is increased among children with speech problems but the risk is mod- erated both by the age at which the speech problems resolve and the nature (and severity) of the speech difficulty. Following on from this, Stackhouse and colleagues (Stackhouse, 2000; Nathan et al., in press) argued that children with speech problems are at risk of literacy problems if they have meta- phonological difficulties, particularly deficits in phoneme awareness. The present study explored the relationship between dyslexia and speech difficulties by assessing the emergent reading-related skills of children with speech difficulties who were receiving speech and language therapy at the time of the study and comparing them with those of children at family risk of reading difficulties by virtue of having an older sibling or parent who was dyslexic. There are now a significant number of studies that have shown the risk of dyslexia is heightened among first degree relatives of people with dyslexia, with between 32% and 65% of the offspring of dyslexic parents going on to have reading problems (Elbro, Borstrom, & Peterson, 1998; Pennington & Lefly, 2001; Scarborough, 1990). Taken together, the findings of these family studies present a fairly unitary picture; the vocabulary skills of children at high risk of dyslexia are poorer than those of controls during the pre-school years (Gallagher, Frith, & Snowling, 2000) and their phonological awareness and letter knowledge are poorly developed at the ages of 4 and 5 years (Gallagher et al., 2000; Penn- ington & Lefly, 2001; Scarborough, 1990). Moreover, there is some evidence that children at family risk of dyslexia show inaccurate articulation of known words (Scarborough, 1990; Elbro et al., 1998). In order to provide a comprehensive assessment of the phonological skills of the two experimental groups, we used tests of phonological learning and phonological awareness as well as assessing basic phonological processes. Given that we selected one group to have speech problems, we predicted that their performance would be less good than that of the children at family risk of dyslexia on a test of output phonological skills, namely nonword repetition. However, in line with previous findings (e.g., Kamhi & Catts, 1986; Gallagher et al., 2000), we expected both groups to perform less well than typically developing children. We included one test of input phonological processing, namely a task in which children had to decide whether a word that they heard was correctly pronounced or not. This task has not, to our knowledge, been used with children with reading disabilities; however, spoken word identification skills have tended to be associated with vocabulary development (Walley, 1993; Metsala & Walley, 1998) and to this extent we predicted that differences between the high-risk participants and controls would turn on their verbal abilities. To assess phonological awareness, we included tests tapping matching phonological segments at the level of syllables, rimes and phonemes. We expected that both high-risk groups would show phonological awareness deficits relative to controls but, in line with the developmental progression of phonological skills, we predicted that these would be more marked for small units (phonemes) than for the lar- ger units of syllables and rimes. We also wished to investigate the ability of the children to learn new words. One of the strongest early predictors of reading ability is letter-knowledge (e.g., Adams, 1990; Muter, Hulme, Snowling, & 632 Julia M. Carroll and Margaret J. Snowling
  3. 3. Taylor, 1998) and children at high risk of dyslexia show poor letter knowledge at school entry (Scar- borough, 1990). To learn a letter’s name or sound requires the association of a visual symbol with a novel phonological form. It is conceivable, therefore, that differences in phonological learning between children with dyslexia and normally developing children could account for differences in their con- solidated knowledge of letters. This hypothesis is particularly appealing in view of the reported diffi- culties that dyslexic children have in visual–verbal paired associate learning (Vellutino, Scanlon, & Spearing, 1995; Vellutino, Steger, Harding, & Phil- lips, 1975). A quite separate body of research shows that children with specific language impairments are slower than children with normal language devel- opment to acquire the meanings of new words in tasks of Quick Incidental Learning Tasks (QUIL; Oetting, Rice, & Swank, 1995; Rice, Oetting, Mar- quis, & Bode, 1994). Although the children studied by these investigators have typically had receptive language impairments, it is at least conceivable that phonological problems contribute to the problem they have in storing new word forms. We therefore predicted that both groups of high-risk children would acquire fewer novel phonological forms (words) in an incidental learning task than controls at low risk of reading difficulties. In summary, we tested the differences between children with family risk of dyslexia and children with speech difficulties in four different domains; literacy, phonological awareness, phonological pro- cessing and phonological learning. It is hypothesised that the children selected for speech difficulties will show weak phonological processing and phonolo- gical awareness, as found by Bird et al. (1995). It is also hypothesised that the children with a family risk of dyslexia will show weak emergent literacy and phonological awareness, as described by Gallagher et al. (2002). In line with the phonological represen- tations hypothesis, it is further predicted that both groups of high-risk children will show weak phono- logical learning (Snowling, Gallagher, & Frith, 2003). Method Participants Fifty-one children aged between 3;11 years and 6;06 years took part in the study. The children comprised three groups of matched triplets; the family-risk group comprised 17 children (6 girls and 11 boys) who had a parent or sibling with diagnosed dyslexia. Each of these children was matched to a child from the speech-impaired group and a child from the control group on the basis of age and, as far as possible, educational experience. The speech-impaired group comprised 17 children (6 girls and 11 boys) who were currently undergoing speech therapy. They were selected by their speech therapists as having signific- antly delayed speech, but average language develop- ment. None of the children in this group had a family history of dyslexia. The control group comprised 17 children (9 girls and 8 boys) who were free of speech difficulties and reported no family history of reading problems. Ten of the children in each group were from state schools or nurseries. Seven of the family-risk and control children were from independent schools, and they were matched to four speech-impaired chil- dren in independent education and three speech- impaired children who were in state education but having speech therapy from a private speech therap- ist. Two of the children in the family-risk group were receiving regular speech therapy. Children from the family-risk and speech-impaired groups were tested either in their homes or in clinics, usually in one or two sessions. The children who acted as controls were tested in their schools. The three groups had equi- valent ages and vocabulary scores, which are shown, together with the descriptive statistics for the other variables, in Table 1. Tests and materials Language skills. Receptive vocabulary: Vocabulary knowledge was measured using the British Picture Vocabulary Scale (long version; Dunn, Dunn, Whetton, & Pintilie, 1982). In this test, the child hears a word and is asked to point out which picture the word depicts from a set of four alternatives. The test continues until the child makes six errors in eight items. Table 1 Performance of family-risk, speech-impaired and control groups on the background measures and experimental tasks Control Family risk Speech impaired Age1 62.53 (9.68) 62.71 (9.86) 62.76 (10.07) Vocabulary2 102.06 (8.53) 104.35 (11.20) 102.59 (13.00) Expressive phonology3 91.89 (5.55) 81.23 (17.38) 62.29 (21.65) Nonword repetition4 17.76 (2.63) 12.47 (4.95) 6.18 (4.49) Mispronunciation detection 5 20.12 (2.67) 17.71 (3.90) 17.18 (4.14) Phonological learning Recognition6 4.94 (1.24) 3.69 (1.85) 3.87 (1.36) Phonological learning Recall6 1.43 (1.16) .50 (.65) .79 (.97) Syllable matching7 13.12 (2.74) 12.41 (2.74) 11.24 (2.88) Rime matching7 14.06 (2.44) 11.76 (3.65) 12.18 (3.86) Phoneme matching7 13.12 (3.44) 11.88 (3.18) 10.13 (3.93) Letter-sound knowledge8 18.88 (8.26) 18.71 (7.99) 14.41 (9.38) Word recognition9 21.18 (17.10) 15.35 (13.94) 12.88 (13.93) Notes: 1 months; 2 standard score; 3 % consonants correct; 4 Max ¼ 24; 5 Max ¼ 23; 6 Max ¼ 6; 7 Max ¼ 16; 8 Max. ¼ 26; 9 Max. ¼ 42. Children at risk of reading difficulties 633
  4. 4. Phonological processing. Mispronunciation detection (input phonology): In this task, the children were intro- duced to a puppet that looked like Cookie Monster, from Sesame Street. They were told that he was a baby monster, who was just learning to talk. Sometimes he said words right, but sometimes he said words wrong. They were asked to listen carefully to what he said and to tell him if he had said each word right or wrong. Three practice items were given, with full feedback, and a brief discussion of what the monster said, and what he was trying to say, to make sure that the child understood the task. The child then heard 23 words. The words varied as to whether they were one-syllable words or three-syllable words, and whether they had a high or low age of acquisition. Eight of the 23 words were correctly pronounced, and 15 were mispro- nounced by substituting a single consonant phoneme. Seven of these had their initial consonant mispro- nounced (e.g., nuck for duck), and eight had a later consonant mispronounced, either a medial consonant (e.g., golilla for gorilla) in the case of the three-syllable words or a final consonant (e.g., moush for mouse) in the case of the one-syllable words. Expressive phonology: In order to provide a measure of the quality of each child’s articulation, his or her responses to items on a confrontation naming task were transcribed and a score representing the percentage of consonants correct was derived (Shriberg & Kwiat- kowski, 1982). The naming task comprised 21 pictures of objects, the names of which had two and three syl- lables with an observed age of acquisition of less than four years. Seven of the words had an unstressed initial syllable (e.g., gorilla), seven of them contained con- sonant clusters (e.g., screwdriver) and seven of them contained vowels as a full syllable (e.g., caterpillar). Eleven of the words were also used in the mis- pronunciation detection task. If a child failed to name an item correctly they were given a semantic clue. If they were still unable to name the picture, they were told the correct name and re-tested on that item at the end of the test. If the child still failed to produce that item then it was assumed that the child did not know that word and it was removed in the calculation of that child’s total score. Nonword repetition (output phonology): The children were also given a nonword repetition task. Nonword repetition is a task that in the school years consistently distinguishes normally developing children from chil- dren with language difficulties (Bishop, North, & Don- lan, 1996). The test consisted of 12 two- and three- syllable nonwords. Eight of these words had primary stress on the initial syllable, e.g., flitherty, 4 of them had primary stress on the second syllable, e.g., bemure. Two points were given for every nonword correctly repeated, and one point for each nonword pronounced with a single phoneme error (an inserted, deleted or substi- tuted phoneme). Phonological learning. To assess phonological learn- ing skills, the child was presented with 6 new words to learn, embedded in the narrative of a storybook, The Gruffalo (Donaldson & Scheffler, 1999). This story de- scribes a monster called a Gruffalo, and then follows a mouse as he searches for the Gruffalo in the forest. Six words were selected from the description of the Gruffalo to be the target words. Four of these were changed from the words in the published story into words not likely to be known by young children. Real words were used for ethical reasons, and pre-testing showed that the words were not generally known to the children. The words consisted of three nouns and three adjectives; wart, talons, tusk, lilac, amber, gnarly. ÔTuskÕ and ÔwartÕ were words present in the original story, but ÔtalonsÕ, ÔlilacÕ, ÔamberÕ and ÔgnarlyÕ replaced ÔclawsÕ, ÔpurpleÕ, ÔorangeÕ and ÔknobblyÕ, respectively. At the beginning of the experiment, the children were shown a picture of the Gruffalo from the book and were asked to point to his ears and to his tail as practice items to make sure that they understood the task. Then they were asked if they could point to each of the target parts of the picture in turn. For instance, they were asked ÔCan you see his talons? Where do you think his talons are?Õ The children were given corrective feed- back. Scores on this part of the test formed the pre-test score. The story was then read to the child with him or her looking at the pictures. To ensure that the children were concentrating on the story, they were given two informal comprehension questions during the course of the book reading, such as ÔWhat animal is this?Õ and ÔWhy is the fox running away?Õ Most children found these questions easy. Each of the target words was included twice in the story, each time accompanying an illustration of that word. Immediately after the first reading of the story, the child was asked to point to the target areas on the picture of the Gruffalo in the same way as they had in pre-testing. Again, corrective feedback was given. After spending at least 30 minutes on other tasks, the chil- dren were shown a picture of the Gruffalo and were asked to recall each of the target words. For instance, the experimenter would point to the Gruffalo’s tusks and ask ÔCan you remember what these were called?Õ Again, they were given corrective feedback. Their per- formance on this task was recorded as the Ôrecall scoreÕ. Finally, they were read the story again, and given an- other recognition test using the picture of the Gruffalo. Responses were recorded to give the Ôrecognition scoreÕ. Phonological awareness. Phonological awareness was assessed by means of three different tests, invol- ving syllable, rime and initial phoneme matching. All of the tasks used followed the two alternative forced- choice format used by Locke (1997). The child was introduced to a puppet who liked to collect words with a particular phonological relationship with the one it al- ready had. For instance, Gerry Giraffe liked to collect words with the same first syllable. For each trial, Gerry held a picture card, and the children were asked, for instance, ÔGerry has a picture of butter. Which of these words, sandwich or button, has the same sound at the beginning as butter ?Õ If the child said they didn’t know, they were encouraged to Ôthink carefully and then chooseÕ. When they had chosen, the cards were turned over to see if they were correct – the correct alternative had a coloured sticker on the back that was the same colour as the cue card. The distracter card had a dif- ferently coloured sticker. If they had picked correctly, the experimenter said, for instance, ÔYes, that’s right, butter and button have the same sound, ÔbutÕ, at the beginning. Sandwich is the odd one out.Õ If they had 634 Julia M. Carroll and Margaret J. Snowling
  5. 5. chosen the wrong alternative, they were told ÔNo, button and butter have the same sound, ÔbutÕ, at the beginning. Sandwich is the odd one out.Õ In this way, the children were given immediate feedback after every trial, as previous researchers (e.g., Content, Kolinsky, Morais, & Bertelson, 1986) had found that feedback on phonolo- gical awareness tasks facilitates understanding of the task requirements. The tasks were presented in sets of eight with feed- back following each trial. Most of the words used were taken from an age of acquisition database (Morrison, Chappell, & Ellis, 1997) as being words of high freq- uency that were in children’s expressive vocabulary at younger than three and a half years of age. The pictures used were in the main taken from the Snodgrass and Vanderwart (1980) picture set. A few words were not from this database, however, and pictures of these words were drawn freehand as black and white line drawings. Syllable matching: The word used for the syllable matching task all had two syllables. In 8 trials, the two words matched according to the initial syllable (e.g., button – butter) and in 8 trials the matching was on the basis of the final syllable (e.g., jigsaw – see-saw). Half of the initial and half of the final matching trials had dis- tracter items that were semantically related to the cue word (e.g., puppy – puppet – rabbit). Rime matching: There were 16 trials in the rime matching task; 8 of these had distracter items that were semantically related to the cue item (e.g., cat – dog – hat), 4 had distracter items that were globally phono- logical similar to the cue item (e.g., pin – tin – pen), 4 trials had distracter items that were unrelated to the cue word. Phoneme matching: In the phoneme matching task the child was required to match items that started with the same initial phoneme (e.g., pen – pig). The task contained 16 trials. On four trials the distracter item was semantically related to the cue word (e.g., sheep – pig – shoe), and on four trials it was phonologically related to the cue word (e.g., dish – beach – duck). On four trials the distracter item was both semantically and phonologically related to the cue word (e.g., moon – sun – mouse), and on four trials it was unrelated to the cue word. Emergent literacy. Letter knowledge: Children were shown each of the 26 lower-case letters of the alphabet individually and asked if they knew what that letter was. If they gave the letter name, they were asked if they knew the letter sound. Letter-sound knowledge was used in the analyses. Reading: To assess early word recognition skills, a test consisting of 42 of the earliest words children learn was given (Hatcher, 2000). Children were shown the words in sets of six and encouraged to read them. The test was discontinued if the child did not know any of the words from the first three sets. Results Mean scores for each group on individual tests are presented in Table 1. To avoid the difficulties asso- ciated with multiple comparisons on a large set of tests, scores on each of the tasks were standardised, and composite scores were created for each area of interest. Group differences were assessed using within-subjects analyses of variance, followed up by planned comparisons between the groups in the form of difference contrasts. Where appropriate, differences between the control group and the two high-risk groups on individual test scores are pre- sented, and differences between the two high-risk groups are discussed in terms of effect size. Phonological processing There was a significant effect of group on the phonological processing composite score (F(2,32) ¼ 25.01, p < .001), which included the measures of expressive phonology (picture naming), nonword repetition and mispronunciation detection. Differ- ence contrasts showed that the three groups differed significantly from each other (control vs. family: F ¼ 18.857, p < .001, family vs. speech: F ¼ 27.907, p < .001), with the family-risk children scoring in between the controls and the speech-impaired chil- dren. As anticipated, both high-risk groups showed difficulties in basic phonological processes, and this was more pronounced for the speech-impaired chil- dren. Differences between the two high-risk groups were large for measures of output phonology (ex- pressive naming d ¼ .97; nonword repetition, d ¼ 1.33), reflecting the selection procedure. In contrast, the subgroup difference on the input measure of mispronunciation detection was small (d ¼ .13). Figure 1 shows the distributions of the scores of the children in the three groups on the expressive phonology (picture-naming) task in terms of per- centage consonants correct. All of the children in the control group scored at least 80% consonants cor- rect. The children with speech difficulties showed a much wider range, from 25% to 96% consonants correct. Six of the 17 children in the family-risk and 13/17 of those in the speech-impaired groups scored below the lowest-scoring control child. Given the fact Control Family-risk Speech-imp. Figure 1 Individual scores on the expressive phonology task by group Children at risk of reading difficulties 635
  6. 6. that the subjects were individually matched, it was not appropriate to use standard 2 · 2 Chi-square analyses, and the data was analysed as 17 pairs in which the control and the at-risk child were either concordant or discordant for the presence of speech difficulties. Both the analyses, for the family-risk and for the speech-impaired groups, were signific- ant, indicating that speech production difficulties were more common in the family-risk group (v2 ¼ 6, df ¼ 1, p < .05) as well as in the speech-impaired group (v2 ¼ 13, df ¼ 1, p < .01). Phonological learning There was a significant effect of group on the Phonological Learning composite (F(2,26) ¼ 6.020, p < .01), which included the recognition and recall measures from the Gruffalo task. In this case, the control children outperformed both the family-risk and the speech-impaired groups (F(1,13) ¼ 7.631, p < .05, and F(1,13) ¼ 19.32, p < .001, respectively), who did not differ from one another (F(1,13) ¼ 2.408, p ¼ ns). Phonological awareness A composite phonological awareness score was cre- ated by summing the standardised scores on the syllable, rime and initial phoneme matching tasks. A main effect of group was again found on this variable (F(2,28) ¼ 4.404, p < .05). Difference contrasts showed that the control children outperformed the family-risk children (F(1,14) ¼ 9.00, p < .01) and the family-risk and speech-impaired children did not differ (F(1,14) ¼ 3.475, p ¼ ns). Examination of the distribution of scores on the phonological awareness tasks suggests that there are larger differences be- tween the control group and the high-risk groups on the rime and initial phoneme matching tasks than on the syllable matching task. Given the non-normal distribution on individual phonological awareness tests, non-parametric tests were used, which con- firmed the hypothesis: there was no significant dif- ference between the groups on the Syllable task (v2 ¼ 4.667, df ¼ 2, p ¼ ns), but there were signific- ant differences on the Rime (v2 ¼ 8.373, df ¼ 2, p < .05) and Initial Phoneme matching tasks (v2 ¼ 8.517, df ¼ 2, p < .05). Effect sizes are not presented, again because of the non-normal dis- tribution of the individual test scores. Literacy measures A composite literacy variable was created by sum- ming the standardised scores of the letter-knowledge and early word recognition tasks. A main effect of group was again found (F(2,32) ¼ 4.189, p < .05). Difference contrasts showed that, contrary to pre- diction, the family-risk group did not differ sig- nificantly from controls (F(1,16) ¼ 1.94, p ¼ ns), but was performing significantly better than the children with speech difficulties (F(1,16) ¼ 5.18, p < .05). However, examination of the mean scores on the reading and letter-knowledge tasks separately pre- sents a somewhat different picture. It is important to interpret sub-group differences cautiously given the high degree of variability, especially in word re- cognition. Nonetheless, further analyses suggest that the family-risk and speech-impaired groups both show lower levels of reading accuracy than controls (F(1,32) ¼ 4.436, p < .05) and do not differ from each other (d ¼ .18). For letter knowledge, there is a trend suggesting an overall group difference (F(1,32) ¼ 3.297, p ¼ .05), with the speech-impaired children having significantly poorer knowledge of letters than the family-risk group (d ¼ .49). Discussion This study explored the similarities in cognitive profile between children with a family history of dyslexia and children with speech problems, in an attempt to assess their relative risk of reading problems. On the basis of previous research, we as- sumed that children in both groups could be con- sidered at high risk of reading difficulties, and predicted that they would show similar weaknesses in phonological skills. In line with this prediction, the performance of the two groups on tests of phonolo- gical processing and phonological learning was im- paired relative to that of controls at low risk of reading failure of similar age and educational experience. The two high-risk groups were also found to have more poorly developed phonological awareness and word recognition skills than controls, and the speech-impaired group had rather less well- developed letter knowledge. The fact that the three groups of children had similar receptive vocabulary rules out the possibility that the phonological difficulties of the two high-risk groups were a consequence of generally poor lan- guage development. Moreover, the two high-risk groups did not differ in their performance on the perceptual task involving the detection of mispro- nunciations in words. Given our recruitment proce- dure, it was not surprising that the children with speech impairments scored more poorly than con- trols on the two tests of output phonology. However, although nonword repetition deficits in the family- risk group were predicted, the degree of impairment in expressive phonology (naming) was unanticip- ated. The difficulties observed in expressive phono- logy and nonword repetition confirmed that output phonological deficits are implicated in the family risk of dyslexia, though these are less severe than those observed among children with speech impairments. Importantly, the two high-risk groups were impaired to a similar degree on a dynamic task requiring phonological learning, in spite of the fact that they 636 Julia M. Carroll and Margaret J. Snowling
  7. 7. were matched with controls in consolidated voca- bulary knowledge on the picture vocabulary test. Although our data do not allow us to draw inferences about causation, these findings suggest that the two high-risk groups have difficulties with the encoding, storage or retrieval processes involved in new word learning. Put another way, they have difficulty in establishing the phonological representations that underlie the accurate retrieval of new phonological forms. We propose such a difficulty implies that, irrespective of whether or not the meaning of a new word can be acquired easily, it will be difficult for these children to retrieve its name. More generally, such a difficulty could explain these children’s difficulty in verbal short-term memory, confronta- tion and rapid naming tasks (Wagner & Torgesen, 1987). As predicted, the difficulties of the high-risk groups were not limited to implicit phonological processes such as nonword repetition. In line with the developmental progression of explicit phonolo- gical awareness, the high-risk groups did not differ from controls in syllable matching but they showed lower performance on the rime and initial phoneme matching tasks. Importantly, in this study, the rime and phoneme tasks contained distracter items mat- ched for global similarity to the cue words. This manipulation precluded the use of a strategy based on overall acoustic similarity to match the target and response items (Byrne & Fielding-Barnsley, 1993). Rather, it was necessary for the child to have access to the segmental structure of the words. Thus, suc- cessful performance on these tasks required access to well-specified, rather than global, phonological representations (Carroll & Snowling, 2001). In line with these findings, Bird et al. (1995) suggested that nonword reading and spelling difficulties observed among speech-impaired children might be explained by the fact that these children still represent words as undifferentiated global wholes, rather than as a series of segmented phonemes. The difficulties that the family-risk and speech- impaired groups showed in phonological awareness when compared with controls confirmed their status at high risk of reading difficulties. In line with this, their concurrent reading attainments were poorer than those of children of the same age and verbal ability, as measured by a test of early word recogni- tion skills suitable for children making their first steps into literacy. As already mentioned, however, an unexpected finding was there was only a trend suggestive of differences between the groups in letter knowledge. Furthermore, contrary to previous re- search (Scarborough, 1990; Gallagher et al., 2000; Byrne, Fielding-Barnsley, Ashley, & Larsen, 1997), children with a family history of dyslexia did not differ from the controls in the number of letter sounds they knew. A feature of the present study that may account for this discrepancy is that most of the children in the family-risk group were recruited because they had an older sibling who had already been diagnosed as dyslexic (and was often receiving intervention). Gallagher et al. (2000) found that parents of children Ôat riskÕ of dyslexia spent more time teaching letters to their pre-school children than parents of control children. It may be that parents who have at least one dyslexic child already are more attuned to the need to help their child learn letters than if their experience of dyslexia was their own and many years ago. In contrast, the parents of children with speech difficulties generally do not associate these oral language problems with a risk of written language difficulties and therefore, it can be surmised, do not train letter skills. Finally, it is interesting to note that, although there is a close relationship between a child’s letter knowledge and their initial sound matching skills (Bowey, 1994; Johnston, Anderson, & Holligan, 1996), the lower performance of the family-risk group could not be accounted for by poor letter knowledge because they were performing within the average range on this test. This finding underlines the fact that children at high risk of reading diffi- culties require training in explicit phonological awareness; tuition in letter knowledge alone is not sufficient to allow them to solve phonological seg- mentation and categorisation tasks. To conclude, the results of the present study confirm the view that children with expressive speech impairments in the absence of language problems are at high risk of reading difficulties and are on a continuum with children at family risk of dyslexia. It is proposed that the shared risk factor is a problem of phonological processing that can be traced to poorly specified phonological representa- tions. According to Walley (1993), vocabulary growth during the pre-school years causes the phonological representations of words to develop from global to segmental form. Segmental phonological represen- tations are required for the development of phoneme awareness and underpin the acquisition of proficient reading skills (i.e., decoding). However, the present findings add to others that point to the fact that there can be a dissociation between vocabulary and phonological skills (e.g., Snowling, Van Wagtendonk, & Stafford, 1988; Swan & Goswami, 1997). Thus, the two groups of children at high risk of reading difficulties presented with phonological processing problems in the absence of vocabulary impairments. In spite of their similar levels of crystallised voca- bulary knowledge, the two high-risk groups shared a deficit in phonological learning that compromised their ability to acquire new words. We propose that this difficulty provides a parsimonious explanation for the range of phonological difficulties they showed. If such children are unable to create seg- mentally organised phonological representations, then their recall of new words will suffer, although they may show fewer difficulties on tests of recogni- tion memory for these novel items. They will have Children at risk of reading difficulties 637
  8. 8. difficulty in discriminating between accurate pro- nunciations of familiar words and pronunciations that are minimally distorted by a single phoneme change. They will also show deficits on tasks that require access to well-specified representations of words in order to match words that share phonolo- gical segments rather than global acoustic similarity with each other. The findings of the present study are consistent with these predictions. Moreover, as has been argued elsewhere (Snowling, 2000b), chil- dren who come to the task of learning to read with poorly specified phonological representations have difficulties in setting up mappings between ortho- graphic and phonological sequences (Harm & Sei- denberg, 1999). The findings of the study also extend the evidence that children with language impairments have diffi- culty with the quick incidental learning of words that are embedded in narrative form (Rice et al., 1994) to the case of children with oral speech impairments. Moreover, their difficulties were more marked for production than for comprehension of these items. It is possible therefore that, in the longer term, these children will begin to show deficits in vocabulary relative to their peers, aggravated by their poor reading skills. Together with the other results of this study, these findings indicate that the remediation of speech difficulties in pre-school and school-aged children is important not only for the successful acquisition of reading but also to ensure the con- tinued normal rate of growth of spoken vocabulary. There are a number of limitations of the present study that could have affected results. First, it is important to note that the study does not speak to the developmental precursors of the speech difficul- ties for which the speech group were being treated. The findings do not rule out the possible relevance of earlier language delays that may have resolved in either of the high-risk groups. Second, the children in this study were studied at a relatively early stage in their literacy development when there is consid- erable variability in performance even in typically developing children. This variability, together with developmental constraints on some of the skills, necessarily reduced the statistical power to detect group differences. Indeed, many of the differences reported for the variables assessed separately are not significant if a strict Bonferroni correction is applied to account for multiple comparisons. How- ever, we would argue that to ignore such group dif- ferences, where these have been predicted, would be overly conservative. Scarborough and Dobrich (1990) have pointed out that there is a tendency, both in research and clinical practice, to overlook subtle impairments in children with language delays when skills, such as reading, are measured at a time when normal development is at a plateau. This argument could be applied to the present data set in which many of the control children gained low scores on the tests of reading-related skills. According to Scarborough and Dobrich, it is when skills are in ÔascendancyÕ and changing rapidly that language- based deficits are more easily detectable. In sum- mary, the present findings are important. Despite the developmental limitations of some of the meas- ures, the study provides clear evidence of difficulties in a range of phonological skills relevant to literacy in these two groups of children at high risk of reading difficulties and argues that there is a continuum of risk between speech difficulties and dyslexia. Acknowledgements This research was carried out as part of the first author’s doctoral work, with support from a BBSRC studentship. Preparation of the manuscript was supported by an ESRC postdoctoral fellowship no. T026271158. 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