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Scientific Studies of Reading

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Poor Reading: A Deficit in Skill-Automatization or aPhonological Deficit?

Heinz Wimmer , Heinz Mayringer & Karin Landerl

To cite this article: Heinz Wimmer , Heinz Mayringer & Karin Landerl (1998) Poor Reading:A Deficit in Skill-Automatization or a Phonological Deficit?, Scientific Studies of Reading, 2:4,321-340, DOI: 10.1207/s1532799xssr0204_2

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SCIENTIFIC STUDIES OF READING, 2(4), 321-340 Copyright O 1998, Lawrence Erlbaum Associates, Inc.

Poor Reading: A Deficit in Skill-Automatization or a

Phonological Deficit?

Heinz Wimmer, Heinz Mayringer, and Karin Landerl University of Salzburg, Salzburg, Austria

This study examined whether the characteristic reading speed impairment of German dyslexic children results from a general skill-automatization deficit sensu Nicolson and Fawcett (1990) or from more specific deficits in visual naming speed and phono- logical skills. The hypothesized skill-automatization deficit was assessed by balanc- ing, peg moving, and visual search. Rapid "automatized" naming tasks served as mea- sures of impaired visual naming speed, and the phonological deficit was assessed by speech perception, phonological sensitivity, and phonological memory tasks. Dys- lexic German children and age-matched control children (all boys) were tested at the end of Grade 2 and as participants of a longitudinal study also at the beginning of Grade 1. No evidence for a skill-automatization deficit was found, as the dyslexic children did not differ at all on the balancing tasks and little on the other nonverbal skill tasks. However, the dyslexic children showed impaired visual naming speed and impaired phonological memory performance that were observed not only in Grade 2 but also before learning to read. Overall, the findings support the conclusion that, even in regular orthographies, difficulties in learning to read are due to a phonological deficit and not to a general skill-automatization deficit.

The reading difficulties of German dyslexic children lend themselves well to an explanation in terms of a general skill-automatization deficit, as suggested by Nicolson and Fawcett (1990). The results of several studies on the readmg deficits of German dyslexic children (Landerl, Wimmer, & Frith, 1997; Wimmer, 1993, 1996a, 1996b) can be summarized in two conclusions. First, German dyslexic chil- dren in contrast to their English counterparts have comparatively little difficulty acquiring phonological recoding as an accurate word recognition procedure, al-

Requests for reprints should be sent to Heinz Wimmer, Hellbrunnerstrasse 34, A-5020 Salzburg, Austria. E-mail: heinz.wimmer@sbg.ac.at

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322 W I M M E R , M A Y R I N G E R , L A N D E R L

though for some dyslexic children this acquisition is delayed. Second, the main reading difficulty of German dyslexic children is a massive speed impairment for all sorts of reading tasks, ranging from frequent words and text to nonwords. In terms of skill-acquisition theory, this pattern of findings suggests that German dys- lexic children have little difficulty setting up phonological recoding as a word rec- ognition mechanism but have d~fficulty in automatizing this and other reading mechanisms. The reason why German dyslexic children in contrast to their Eng- lish counterparts have little difficulty acquiring phonological recoding is obvious. First, German in comparison to English orthography exhibits rather simple and straightforward grapheme-phoneme relations (vowel graphemes in particular); second, German children are exposed to systematic synthetic phonics instruction that directly imparts phonological recoding as a word recognition procedure.

This study examined the skill-automatization deficit explanation for German dyslexic children and contrasted it with the well-known phonological deficit ex- planation. We selected dyslexic boys, who displayed the typical German reading difficulties-that is, a massive reading speed impairment-and tested them with a battery of motor skill tasks, specifically with the balancing tasks, which, according to Nicolson and Fawcett (1990, 1995), measure automatization deficits when con- scious effort to compensate is prevented. The children were also tested with a bat- tery of phonological tasks including speech perception, phonological sensitivity, and phonological memory. A third set of tasks was rapid automatized visual narn- ing tasks, which, according to recent theorizing by Bowers and Wolf (1993), as- sess a deficit independent of phonological segmentation.

The main line of reasoning now is as follows. From the automatization deficit explanation, it follows that these dyslexic children should exhibit uniformly de- pressed performance over all three sets of tasks, because the general skill-automatization deficit should affect all domains of processing. The most clear-cut deficit should be for skills with the highest level of automatization in nor- mally developing children. Balancing would constitute the prototypical case of a completely automatized skill in normally developing children and, as the results of Nicolson and Fawcett (1990, 1995) suggest, is not fully automatized in dyslexic children. In contrast, the phonological deficit explanation (and also the double def- icit explanation; Bowers & Wolf, 1993) is more specific. The deficit of dyslexic children would be located in the phonological domain, and deficits in the domain of motor skills would not be predicted.

METHOD

The data reported here stem from two assessments. The first assessment of cogni- tive deficits was done shortly after school entrance (fall 1994), when the children of the present sample were tested as participants of a large-scale longitudinal study

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POOR READING 323

on precursors of reading difficulties. The data from the first assessment are useful, as they were gathered before major reading difficulties emerged, and therefore any cognitive impairment cannot be interpreted as a consequence of already existing differences in reading skill. The second cognitive assessment was done at the end of Grade 2 (June 1996) and was particularly aimed at examining the skill-automatization deficit explanation.

Participants

The 20 dyslexic and 27 control children of this study were selected in the middle of Grade 2 and, with theexception of 1 dyslexic boy and 2 controls, were recruited from a longitudinally traced sample of about 600 boys who had been tested at the begin- ning of Grade 1. By relying exclusively on boys, we hoped to increase the number of children with reading difficulties. All of the children attended schools in the city of Salzburg or in neighboring communities and spoke German as their native language. For the selection of the present group, we relied on an assessment of the whole sam- ple (now reduced to 525 boys) in the middle of Grade 2. At this time, a classroom word reading test and a spelling test were applied, and teachers were asked to norni- nate children with unexpected readmg or spelling difficulties in their classrooms. Children nominated by their teachers were further tested with an individual stan- dardized reading test developed in our laboratory (Landerl, Wimmer, & Moser, 1997). For the 20 boys who finally served as dyslexic participants, the judgment of the teachers was confirmed by apercentile rank of lower than 20 of the reading time score for two subtests of the standardized reading test. One was the frequent words subtest, in which children have to read aloud quickly and accurately alist of 30 short, frequent content words such as Vater ("father"), Apfel ("apple"), and Milch ("milk"). The text subtest required reading aloud acoherent descriptive passage also consisting of 30 words. The choice of these particular subtests for selection was based on the assumption thatreading frequent words anda simple text will reflect the difficulties a child might encounter in classroom reading tasks. The choice of im- paired reading speed as a selection criterion was based on Wimmer's (1993) finding that dyslexic German children from Grade 2 onward exhibit only few reading errors but suffer from severely impaired reading speed.

Exclusion criteria for the present sample were general intellectual impairment (IQ below 85 on Raven's Colored Progressive Matrices), indications of attention deficitlhyperactivity problems, and prolonged absence from school. Information on the latter two criteria was gathered from interviews with the mothers. The 27 control children were judged by their classroom teachers as showing no reading problems.

Table 1 shows the reading and spelling performances, Raven IQ, Wechsler In- telligence Scale for Children-Revised (WISC-R) Vocabulary score, and age for the 20 dyslexic and 27 control children.

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TABLE 1 Descriptive Characteristics of Dyslexic Children and Control Children

Measure

Dyslexicd control"

M SD Percentile M SD Percentile

Individual reading Frequent words

Speed (seclword) Errors (%)

Text Speed (seclword) Errors (%)

Spelling errors (%) Intelligence (Raven) Vocabulary (WISC-R) Age (years, months)

-- -

Note. WISC-R = Wechsler Intelligence Scale for Children-Revised. an = 20. bn = 27.

The upper section of Table 1 gives the reading performance of the dyslexic and control children on the two subtests of the individual reading test that were used for the selection of dyslexic children. Table 1 shows that, for the frequent words subtest, the mean reading time per word of the dyslexic children was close to 3 sec and about four times as high as that of the control children; similarly, for the text subtest, the mean reading time per word of the dyslexic children was about three times as high as the mean of the control children. For both subtests, however, even the dyslexic children showed few errors. The errors tended to be minor deviations from the grapheme sequence-for example, Voge (a nonword) instead of Vogel and nach (a word) instead of Nacht. Not a single case of reading refusal occurred. The typical observation from the individual reading test was that the dyslexic chil- dren very slowly and effortfully recoded the majority of the words, whereas the control children read most words fluently without manifest signs of recoding. Based on our experience with dyslexic children both in research and remediation, we can say that the reading difficulties of the present sample were quite typical for Austrian dyslexic children at the end of Grade 2. Very infrequently, we saw chil- dren who in the second half of Grade 2 had not yet acquired basic recoding abili- ties. In the present sample, there was no such child.

The reading problem of the dyslexic children was accompanied by a spelling problem as evident from the high mean error percentage in Table 1. However, it is important to note that the large majority (8 1 %) of the orthographically incorrect spellings of the dyslexic children were phonetically acceptable. This is possible be- cause German orthography is more consistent in the grapheme-to-phoneme direc-

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POOR READING 325

tion than vice versa. For example, the vowel changes in plural forms are marked in the conventional spellings by umlauts, as in Ball-Balle ("ball"-"balls"). The um- lauts mark the change of vowel sound from Id to Id but permit keeping the letter se- quence of the morpheme (i.e., of Ball) intact. The resulting problem in spelling is that the most direct and simple transcription of the vowel Id would be the grapheme ce>, resulting in the phonetically correct but orthographically wrong spelling Belle.

From the percentile ranks corresponding to the mean reading and spelling per- formance of the control children in Table 1, it is obvious that this comparison group consisted of more or less average readers and not of particularly good read- ers. The lower part of Table 1 shows that the dyslexic children scored in the normal range both on Raven's Matrices, based on norms for German children (Schmidtke, Schaller, & Becker, 1978), and on the German version of the WISC-RVocabulary test (Tewes, 1983). The WISC-R scale has a mean of 10 (SD = 3). In summary, the present dyslexic boys exhibited the reading speed impairment characteristic for German dyslexic children. The reading difficulties were registered by the teacher and were ascertained by an individual reading test. The reading difficulties were specific in the sense that they were not accompanied by low nonverbal IQ or low vocabulary scores. Further, attention deficit was ruled out as a potential cause of the reading dfficulties.

Procedure

The first cognitive assessment (of participants of the large longitudinal sample) was done in the first 2 months of Grade 1, which begins in the second week of Sep- tember, in a quiet room at the school. This first assessment can be considered to be before or in the very early phase of reading instruction because, in Austria and Germany, there is no reading preparation in kindergarten and in-school reading in- struction begins very slowly. At the end of the testing period, not more than about five or six letters were introduced in the more advanced classrooms. There was no difference between dyslexic and control children with respect to the number of weeks (after the beginning of school) when the first assessment was done. The sec- ond assessment (end of Grade 2) was done at the Institute of Psychology because of the equipment required for the speech perception task (to be described).

Tasks

Nonverbal Skills

Peg moving (Grade 1). This task was modeled after Annett (1985). The child's task was to move as quickly as possible 10 pegs from one line of holes in a wooden frame into the holes of a second line. The time for one such trial was taken.

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The task consisted of two alternating trials for each hand. The retest reliability, computed for the sum of the first trials (for right and left hands) and the sum of the second trials, was .78. The total time for all four trials was used as the dependent variable.

Visual search (Grade 1). The visual search task is a subtest of a standard- ized Austrian school entrance examination. The child was presented a worksheet with seven lines of 12 differently oriented apples each. The child's task was to iden- tify those apples that are oriented like the sample at the top of the worksheet. The child was instructed via a practice task to cross out the correctly oriented apples and to work through each line from left to right. Errors were very infrequent; therefore, performance time was used as measure.

Balancing (Grade 2). This task was modeled after Nicolson and Fawcett (1990, 1995) and consisted of three conditions. In each condition, the child had to stand on one leg on a balance beam (8 cm high, 13 cm wide, 60 cm long) for 30 sec with each leg. The sight condition was followed by a dual-task condition and a blindfold condition. In the dual-task condition, the child was presented with a se- quence of nouns from an audiotape (one noun every 2 sec) and had to indicate (with averbal "yes" or "no") whether the noun denotes an animal (half of the nouns do).

Balancing with stretched-out arms (as done by Nicolson & Fawcett, 1990, 1995) was too strenuous for the present young children. Therefore, they were in- structed to keep their arms straight down beside their legs. Movements of each arm and each leg were taken into consideration. The scoring system followed the one used by Nicolson and Fawcett and was based on video records. Arm movements up to 15' were tolerated. If a child moved an arm up between 15" and 30°, half an error point was given. For arm movements between 30" and 50°, 1 error point was given. If a child moved his arms up higher than 50" or tapped the floor with his free foot, 2 error points were given. If a child set his free foot on the floor and placed his full weight on it, or if he was off the beam with both feet, 3 error points were given. To make scoring of the arm movements easier, the child performed in front of a large poster on which, for each shoulder joint, the arm sections corresponding to 15", 30°, and 50" were marked. Two raters independently scored balancing perfor- mances of 5 children in the blindfold condition. Cohen's Kappa (for 300+ wob- bling events) was .72. For each of the three conditions, the wobble scores for left- and right-leg balancing were combined.

Visual Naming and Articulation

Object naming (Grade 1). This task, modeled after Denckla and Rude1 (1976), consisted of two trials. For each trial, a random sequence of 20 object pic- tures (5 different pictures, each repeated four times) had to be named. The pictures

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POOR READING 327

for one trial were presented on a single page with four lines of 5 objects on each page. From one line to the next, the order of the 5 objects changed. The words of the first trial all started with a different consonant cluster (Kran, Frosch, Blatt, SchloJ, Brut), whereas the words of the other trial all started with the same single consonant (Buch, Bett, Bar, Baum, Ball). Two practice trials preceded each of the two test tri- als. The first practice trial introduced the 5 pictures, and the child was asked to name them. In case of difficulties, the experimenter provided the intended words. The second practice trial consisted of two lines with 5 objects each, and the child was in- troduced to the rapid naming procedure. On the two test trials, errors were very in- frequent and most often immediately corrected by the child. Therefore, only nam- ing time was used as a measure. The correlation between the naming time scores for the two test trials was .66. As the dependent variable, the sum of naming time for the two trials was used.

Digit naming (Grade 2). This task corresponded exactly to the original Denckla and Rude1 (1976) digit naming task. Ten lines with five digits (2,4,6,7,9) arranged in different order from line to line were presented and were to be named as quickly as possible. For practice, two lines were given.

Articulation speed (Grades 1 and2). The articulation speed tasks, ad- ministered at the same time as the corresponding naming task, should control for the possibility that naming speed differences between dyslexic and con- trol children were due to articulation speed differences. To control for object nam- ing speed differences, the children performed an articulation task with object tri- ples. Triples of closely associated words were used to reduce memory load-for example, Hund-Katze-Maus ("dog7'-"cat9'-"mouse") and Messer-Gabel-Lhffel ("kniveV-"fork"-"spoon"). The children were first presented with the three words, which they had to repeat. Then they were asked to repeat each word triple as often as possible within 10 sec. The correlation between the two trials was .60. To control for articulation speed in digit naming, the children were asked to count from 1 to 10 as quickly as possible. Two such countings had to be performed; the correlation was .81. The two trials of each articulation speed test were combined, and a com- mon measure of time to articulate an item was used.

Phonological Sensitivity

Rhyme detection (Grade 1). For each of the 15 items on this task, the task format was as follows: "What rhymes with Feld? Geld or Gold?' The nonrhyming answer differed from the rhyming answer only in either the vowel or the final con-

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328 WIMMER, MAYRINGER, LANDERL

sonant. The task was introduced by three practice items, for which corrective feed- back was given. Split-half reliability, corrected for test length, was .73.

Alliteration detection (Grade I). For alliteration detection, we tried a task format analogous to that of rhyme detection (i.e., "Which word begins like Gold: Feld or Geld?') but found this to be too difficult. So, instead, we used a task format that directly specified the initial syllable or the initial consonant (8 items each). An example for the former is "Maler-Nagel-baden: Which word starts with /ma/?'; an example for the latter is "Mutter-Nadel-Beeren: Which word starts with lml?' The syllable items still required alliteration detection because the three choices always shared the first vowel, so that the correct word could be identified only via the initial consonant. For the initial consonant items, a continuant was always used as the tar- get segment in order to facilitate perception. To minimize memory load, each item was accompanied by pictures for the three words. The syllable items were always presented before the single-consonant items, each preceded by two practice items. Split-half reliability, corrected for test length, was .74.

Speech Perception (Grade 2)

The two tasks used for assessing deficits in speech perception differed only in the way the speech signal was masked. In the party-noise task, the test sentences were masked by increasing levels of background party noise. In the simulta- neous-speaker task, the test sentences were masked by a second sentence, simulta- neously spoken by a speaker of the other sex. The test sentences for each subtask were simple and short (between four and seven words), so that memory should not be a problem.

Party-noise background. In the party-noise task, the 16 test sentences were embedded in four increasing levels (4 sentences per level) of the same party-type background noise. The items were produced with computer sound software, which was used to combine recorded test sentences with different levels of the same back- ground noise (a record of a cafeteria environment). Based on pretests to determine appropriate levels of difficulty, the original cafeteria noise was intensified to 160% for the first noise level and to 180%, 200%, and 220% for the three following noise levels. Immediately before each test sentence, a gong sound served as the warning signal. Two practice sentences were used to familiarize the child with the proce- dure. In case the child was unsure what he had heard, guessing was encouraged. Be- cause noise levels did not interact with group, we used the percentage of correctly

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POOR READING 329

repeated words across all four noise levels as the speech perception measure. Split-half reliability was .70 (corrected for test length).

Simultaneous-speaker background. For the subsequently administered simultaneous-speaker task, the experimenter first introduced drawings of a man and a woman. She then explained that both a male and a female voice would be heard simultaneously and that the child should repeat only the sentence of the speaker that was pointed at (half the time, it was the male speaker; the other half, it was the female speaker). For the first group of 10 sentences (preceded by 2 practice sentences), the experimenter specified the speaker before presentation of the two simultaneously spoken sentences. For the second group of 10 sentences (also pre- ceded by 2 practice sentences), the speaker was specified after the presentation. The sentences by the male and female speakers were separately recorded, and the simul- taneous version was created in such a way that the male and female voices started and ended at the same moment. Again, because of the absence of an interaction be- tween task factors and group, the measure used the percentage of correctly repeated words. Split-half reliability, corrected for test length, was .79.

Memory

Pseudoword repetition (Grade 1). The 15 items of this task required im- mediate repetition of three-syllable pseudowords (e.g.,fiwofi, bowiba). The idea was to induce assimilation errors for the one syllable of a pseudoword that did not share the onset of the two other syllables (e.g., fifoji produced for fiwofi). The pseudowords were presented by the experimenters. Four practice items were given. Split-half reliablity, corrected for test length, was 35 .

Pseudoword recall (Grade 2). Here, 12 sequences of pseudowords had to be repeated. The first 6 sequences consisted of two pseudowords each; the second 6 sequences consisted of three pseudowords each. All of the pseudowords were of consonant-consonant-vowel-consonant (CCVC) structure. Half of the items con- sisted of pseudowords beginning with the same consonant (e.g., pras-plit, klaf-knis-kwun); the other half consisted of pseudwords beginning with a different consonant (e.g., knes-blo$ schwopp-klaf-bripp). The items were presented via sound software and headphones. Presentation of each item was started separately as sloon as the child was concentrating, and it was preceded by a gong sound. The per- formance measure was the percentage of correctly repeated pseudowords. Split-half reliability, corrected for test length, was .71.

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330 WIMMER, MAYRINGER, LANDERL

Pseudoname learning (Grade 2). This task was originally planned as the learning phase of a rapid naming task with the idea to assess naming speed for newly learned associations between pictures and words. However, it turned out that learning the new names was too difficult for a number of the dyslexic children. Therefore, only the learning phase provided useful results.

The children had to learn the names of three invented animals. First, children were simply shown pictures of the animals; then, in the first learning trial, each an- imal was presented separately with its name. The three names werefilo, kogan, and spurk. Each name had to be repeated immediately. No repetition errors oc- curred. The name was then affirmatively repeated by the experimenter. After this introduction of the names, the test trials consisted of asking the children for the names of the three animals, which, on each trial, were presented one by one in ex- actly the same sequence in which they were originally introduced. In the case of a missing or incorrect response, the name was given, and the child was asked to re- peat and remember it. This procedure continued until all three animals were named correctly within the same trial. The upper limit of trials was 20. In several cases, the task had to be finished before 20 trials either because the child wanted to quit or because it was obvious that the task became very frustrating. Because we had not anticipated the difficulty of what was planned as the learning phase of a naming speed task, only the number of trials and not all the naming responses was noted. Number of trials was thus used as the learning measure. The lowest possible num- ber was 1, if a child required only the presentation trial and named all three animals correctly on the first test trial. If the task had to be finished before meeting the learning criterion or reaching the upper limit of 20 trials, 3 additional trials were added under the conservative assumption that, with these additional trials, the child would have responded correctly to the three animals within a trial.

RESULTS

Table 2 shows the performance of dyslexic and control children for nonverbal slulls, visual naming, and phonological skills. To allow easier comparison of tasks, performance measures were converted into percentages correct or into processing time per item whenever possible. Because of space limitation, we do not report in detail the results of the analyses of variance (ANOVAs) that examined the interac- tions between the task factors (mentioned in the description of the tasks) and the group factor. All of these interactions were nonsignificant.

Nonverbal Skills

Because of the obvious differences between the balancing tasks and the visuomotor speed tasks (peg moving and visual search), the group differences for the two types of tasks were analyzed separately with a multivariate ANOVA

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POOR READING 331

TABLE 2 Means and Standard Deviations of Dyslexic Children and Control Children

on Verbal and Nonverbal Tasks

Dyslexic Control

M SD M SD Task

Nonverbal skills Peg moving (sec) Visual search (sec) Balancing (wobble score)

Sight Dual task Blindfold

Visual naming and articulation Naming (seclitem) Objects Digits Articulation (sectitem) Objects Digits

Phonological sensitivity Rhyme detection (%) Alliteration detection (%)

Speech perception Party-noise background (%) Simultaneous-speaker background (%)

Memory Pseudoword repetition (%) Pseudoword recall (%) Pseudoname learning (trials)

(MANOVA) for each set of measures. For each of the MANOVAs, Wilks's lambda is given, indicating the within-group variance in relation to the total vari- ance. A high lambda value indicates that the difference between dyslexic and con- trol children adds little variance to the within-group variance. The MANOVA with the two visuomotor speed scores as dependent variables gave no reliable group ef- fect, Wilks's h= .95, F(2,41) = 1.1, p > .30. From the means in Table 2, it is evi- dent that the dyslexic children performed only slightly slower than the control chil- dren. An additional observation was that the dyslexic children did not differ from the control children in the mean number of errors on the visual search (dyslexic = 1 .O, control = 1.6).

The MANOVA with the three balancing scores as dependent variables also gave no reliable group effect, Wilks's h = .98, F(3,43) < 1. From Table 2, it is ob- vious that balancing in the blindfold condition led to much more wobbling than in

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the other two conditions. However, the increase in wobbling was about the same for the dyslexic as for the control children. Most important, in the dual-task condi- tion, the dyslexic children actually tended to perform better (i.e., smaller mean wobbling score) than the control children

Visual Naming and Articulation

Table 2 shows that the mean naming time of the dyslexic children was much higher than that of the control children on the two visual-naming tasks, Wilks's h = .70, F(2, 41) = 8.8, p < .01. The group difference was reliable for both the ob- ject-naming task at the beginning of Grade 1 and the digit-naming task in Grade 2, Fs(l,41) = 12.3 and 13.9, respectively,~ < .01. The MANOVA for the two articu- lation speed variables gave no reliable difference between dyslexic and control children, Wilks's h = .92, F(2,41) = 1.8, p > .15. Table 2 shows that there was al- most no difference for counting speed.

Phonological Skills

Group differences were examined separately for the two phonological sensitivity measures, the two speech perception measures, and the three memory measures. For rhyme and alliteration detection, no reliable deficit of the dyslexic children was found, Wilks's h = .95, F(2,41) = 1.08, p > .30. From the means in Table 2, it is evident that the tasks were rather easy for both dyslexic and control children. It should be remembered that the means expected from guessing because of the dif- ferent number of alternatives are different for the two tasks, with 50% correct for rhyme detection and 33% correct for alliteration detection.

There was also no deficit of the dyslexic children for the two speech perception measures, Wilks's h = .92, F(2,44) = 1 . 8 , ~ > .15. In contrast, the memory perfor- mance of the dyslexic children was markedly impaired, Wilks's h= .64, F(3,40) = 7.4, p < .001. The univariate tests showed that dyslexic children scored lower on pseudoword repetition, F(1, 42) = 13.3, p < .001, pseudoword recall, F(l, 42) = 7.0, p < .05, and pseudoname learning, F(1,42) = 14.6, p < .001. Table 2 shows that the dyslexic deficit was rather small for the pseudoword recall task. Further analysis of this task showed that the deficit of the dyslexic children resulted mainly from items consisting of two pseudowords (dyslexic = 71% correct, control = 85% correct). In contrast, there was hardly any deficit of the dyslexic children for the items consisting of three pseudowords (dyslexic = 55%, control = 59%). Appar- ently, the items consisting of three pseudowords were nearly as difficult for the control children as for the dyslexic children. However, the interaction between

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POOR READING 333

item length (two vs. three pseudowords) and group did not reach a significant level, F(1,45) = 3.0, p = .09.

Group Effect Sizes

A summary of the cognitive deficits of the dyslexic children is presented in Ta- ble 3. The measures are ordered according to effect size-that is, according to the means of the individual z scores of the dyslexic children. The z scores were com- puted by dividing the difference between a test score and the mean of the control group by the standard deviation of the control group. The z scores were poled in such a way that a negative sign indicates poorer performance. In addition, Table 3 shows the percentages of dyslexic and control children whose performance was at least 1 SD below the mean of the control group (indicative of poor performance).

Effect sizes with an absolute value larger than 1 were found for the two visual naming speed measures and for the three phonological memory mea- sures-pseudoname learning, pseudoword recall, and pseudoword repetition. For pseudoword recall, however, it must be noted that only performance for two-word items is given here because, as mentioned before, the difference between dyslexic

TABLE 3 Group Effect Sizes and Incidences of Poor Performance

Incidence (%) of Poor Performance

Task Effect Size Dyslexid ~ontrolb

Naming (digits) Naming (objects) Pseudoname learning Pseudoword recallC Pseudoword repetition Articulation (objects) Speech perception (party noise) Alliteration detection Peg moving Visual search Rhyme detection Articulation (digits) Balancing (sight) Balancing (blindfold) Speech perception (second speaker) Balancing (dual task)

an = 20. bn = 27. COniy for items consisting of two pseudowords.

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and control children was more marked for these items. Table 3 also shows that, only for these five measures with an absolute effect size larger than 1, the percent- age of children with poor performance was much higher in the dyslexic group than in the control group. In contrast, for the visuomotor speed measures (peg moving and visual search), effect size was somewhat below 0.5, and, for the balancing measures, effect size was around 0.

DISCUSSION

Before going into detailed discussion, implications of the general pattern of find- ings should be mapped out. First, the findings obviously speak against the skill-automatization deficit explanation of dyslexia. Expectations were that dys- lexic children should exhibit uniformly depressed performance over all tasks, be- cause of the general nature of the postulated skill deficit. The most clear-cut deficit was expected for balancing, being the skill with the highest level of automatization in normally developing children. Obviously, the findings were quite different. In particular, the dyslexic children showed no deficit at all on the balancing tasks. Second, the observed pattern is in general agreement with the main implication of the phonological impairment explanation and the double-deficit explana- tion-namely, that the deficit of the dyslexic children should be specific to the phonological domain. However, the phonological impairment seemed to be limited to tasks that heavily involve language production (naming speed) or pho- nological memory plus language production (pseudoword repetition, pseudoword sequence recall, pseudoname learning). No reliable deficits were found for recep- tive language skills as measured by the speech perception task and the phonologi- cal sensitivity tasks.

Nonverbal Deficits

It came as a surprise that we were unable to replicate the balancing problems of dyslexic children reported by Nicolson and Fawcett (1990,1995) and Yap and Van der Leij (1994). As pointed out in our Introduction, the specific assumption of Nicolson and Fawcett is that dyslexic children exhibit problems with balancing, particularly when they are prevented from compensating for the difficulty in the dual-task condition. As noted in our Results section, there was no difference at all between dyslexic and control children in the dual-task condition, with dyslexic children actually showing slightly less wobbling than control children in this con- dition. One might hypothesize that our dual-task condition (semantic category judgments) was not demanding enough. This is rather implausible, as the observed high percentage of correct category judgments seems possible only when the

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words, which were presented at 2-sec intervals, were attended to. Further, in the blindfold condition, visual information on which compensatory efforts could be based was simply not available. Indeed, there was a sharp drop in balancing perfor- mance in this condition, but this drop was the same for dyslexic and control chil- dren, with the dyslexic children performing again slightly better than the control children.

A follow-up study in our laboratory (Raberger, 1996), with somewhat older dyslexic children (in contrast to this study), found a balancing deficit of the dys- lexic children. However, compared to Nicolson and Fawcett (1995), the difference between dyslexic and age-matched control children was small and no longer reli- able when attention deficit hyperactivity disorder (ADHD) differences between the two groups were controlled for. The association between ADHD and balancing difficulties is not suprising, because ADHD children should have difficulty trying to stand still on the balance beam. It should be remembered that, in the selection of the present sample, we excluded poor readers from our sample when the mother had mentioned attention deficitlhyperactivity problems. Therefore, the discrep- ancy between the present results and those of Nicolson and Fawcett (1990, 1995) and Yap and Van der Leij (1994) may have to do with the exclusion of ADHD chil- dren from the present sample (no such exclusion of ADHD children was men- tioned in those previous studies).

The other findings on nonverbal skill deficits of our dyslexic children are also negative. Ofparticular importance is thatthere was noreliabledyslexic deficit on the two visuomotor speed tasks (i.e., peg moving and visual search). Such a deficit should be observed if the reading speed problem is caused by a general deficit with the fast execution of any skill. We found only small and nonreliable trends for slower performance, but the large majority of the dyslexic children exhibited processing speed in the nonnal range on these tasks. The present finding stands in contrast to Fawcett and Nicolson (1995), who founddyslexic children to be impaired on the peg moving task and on abeads threading task. We note that apparently the dyslexic chil- dren participating in Fawcett and Nicolson's study were the same children who ex- hibited the balancing problems described by Nicolson and Fawcett (1995). Therefore, again, the exclusion of ADHD children from the present sample may be a possible explanation of the absence of a visuomotor deficit observed here.

Visual-Naming and Articulation Speed Deficits

The impaired performance of our dyslexic children on the rapid-naming tasks cor- responds to other findings of naming speed deficits of German dyslexic children (Wimmer, 1993; Wolf, Pfeil, Lotz, & Biddle, 1994) and is in agreement with the consistent findings of visual naming speed deficits of English dyslexic children (review by Bowers &Wolf, 1993). The present findings also show that the naming speed deficit cannot be accounted for by an articulation speed deficit, as the dys-

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lexic children did not differ from the controls on the two articulation speed tasks. In particular, in Grade 2, there was no difference at all between the dyslexic and the age-matched control children on the counting speed task. This makes it unlikely that the dyslexic deficit on the digit-naming task is simply reflecting the reading deficit of the dyslexic sample. Direct evidence against such an interpretation is the finding that the naming speed deficit of the dyslexic children (on the ob- ject-naming task) was already present at the beginning of Grade 1-that is, at a time when the reading advantage of the control children could only be small be- cause of the lack of any reading preparation in kindergarten and because of the very slow reading instruction in school.

Phonological Deficits

Unexpectedly, phonological deficits of our dyslexic sample were more or less lim- ited to the memory tasks and were not evident on the speech perception and phono- logical sensitivity tasks. With respect to speech perception, it should be noted that our task is rather crude compared to the categorical phoneme perception method used in other studies that found perception deficits in dyslexic children (e.g., Reed, 1989; Werker & Tees, 1987). Nevertheless, it is astonishing that our dyslexic chil- dren did not differ at all from age-matched controls when having to attend to one of two simultaneously occurring speech inputs. On the party-noise task, there was a difference in the expected direction, but it was small and not reliable. The absence of a dyslexic deficit on the simultaneous-speaker and party-noise tasks cannot be explained by the presence of ceiling or floor effects, as the perception tasks showed appropriate difficulty levels. The negative findings from the speech per- ception tasks are further strengthened by the corresponding negative findings from the assessments of rhyme and alliteration detection. These tasks require not only phonological awareness but also exact phoneme discrimination because the cor- rect alternative differed in only one phoneme from the incorrect one(s), and, fur- ther, often these two critical phonemes were similar. For example, in half of the rhyme items (e.g., "What rhymes with Feld: Gold or Geld?'), the alternatives dif- fered only in the vowel; in the other half, the alternatives differed in the final simi- lar consonants (e.g., "What rhymes with Dieb: Sieb or Sieg?'). This was also the case for the alliteration items. For example, in "Buben-Dusche-Nudel: Which word begins with /du/?', the /dl has to be discriminated from the quite similar con- sonants /b/ and /n/.

Even more unexpected than the absence of a speech perception deficit was the absence of a phonological awareness deficit in the later dyslexic children (begin- ning of Grade 1). This finding differs from Bradley and Bryant (1978), who, for English dyslexic children, found remarkable deficits on a oddity detection task for rhyme and alliteration. In Bradley and Bryant's oddity detection procedure, the child has to identify which word does not share a crucial segment with the rest. For

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example, in nod-red-fed-bed, the child has to recognize that nod does not rhyme with the others. Obviously, finding the nonrhyming word (in contrast to finding the rhyming word) and the associated memory load make this task more complex than ours. A previous study with older German dyslexic children used Bradley and Bryant's rhyme oddity detection task and found a small deficit compared to age-matched control children (Wimmer, 1993).

Theoretically more interesting than deficits in early alliteration and rhyme awareness would be deficits in phoneme blending and segmentation, because the children of this study were exposed to a phonics-oriented teaching approach that focuses exactly on these sllls. Wimmer (1996a) indeed found difficulties with phoneme blending and segmentation at the end of Grade 1 in a retrospective analy- sis of early (i.e., end of Grade 1) difficulties of children who later were diagnosed as dyslexic. However, at the beginning of Grade 1-the time of the present first as- sessment-it makes no sense to assess phoneme blending and segmentation in German children, as the large majority of them is completely unable to pass such tasks because of the absence of any reading preparation in kindergarten (Wimmer, Landerl, Linortner, & Hummer, 199 1).

In contrast to the results involving speech perception and phonological awareness, our dyslexic children showed serious difficulties with pseudoword repetition, pseudoword sequence recall, and pseudoname learning. Similar defi- cits for pseudoword repetition and pseudoword recall have been reported for English dyslexic children (Brady, Mann, & Schmidt, 1987; Brady, Poggie, & Rapala, 1989; Snowling, Goulandris, Bowlby, & Howell, 1986) and for Dutch dyslexic children (Van Bon & Van der Pijl, 1997). Wimmer (1993) found no re- liable pseudoword repetition deficit for another sample of German dyslexic chil- dren. The difficulty level of the task seems to be crucial for detecting the dyslexic deficit because, in this study, we also found no deficit for the more dif- ficult pseudoword recall items (consisting of three pseudowords), on which con- trol children also scored rather low. The difficulty of the pseudoname learning task for our dyslexic children corresponds to similar findings for Eng- lish-speaking children with reading deficits (Aguiar & Brady, 1991; Gathercole & Baddeley, 1990; Vellutino, Steger, Harding, & Phillips, 1975).

Again, as in the case of the naming speed deficit of the present dyslexic chil- dren, we note that the memory deficit (for the pseudoword repetition task) was al- ready observed at the beginning of Grade l , before reading instruction. This again rules out that the memory deficit is a consequence of the reading deficiency.

Relationship to Difficulties in Learning to Read

How could the deficits in naming speed and phonological memory processes cause the difficulties in learuing to read? This question is all the more important because we did not find serious phonological awareness difficulties before reading instruc-

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tion, and, in the middle of Grade 2, we did not find major phonemic segmentation difficulties among our dyslexic children. Phonemic segmentation was not directly tested, but the absence of serious difficulties in the middle of Grade 2 can be in- ferred from the finding that the large majority of the dyslexic children's ortho- graphically wrong spellings were produced in a phonetically acceptable way. Fur- ther, Wimmer (1993), for a similar sample of dyslexic Grade 2 children, directly showed high performance on a pseudoword spelling task and on a vowel substitu- tion task. These findings suggest that the reading and spelling difficulties of Ger- man dyslexic children are not predominantly resulting from impaired access to the phonemic level of speech.

Our proposal is that the naming speed deficit and the phonological memory def- icit are linked to difficulties in learning to read via the difficulty in establishing memory representations for the letter sequences of words or of parts of words. That disabled readers indeed have massive difficulties in establishing memory representations for the letter sequences of words was directly shown by Ehri and Saltmarsh (1995) and Reitsma (1983). To explicate the role of the naming speed deficit, we follow Bower's (1995) recent proposal that establishing memory repre- sentations for the letter sequences of words cannot proceed smoothly if activation of the phonemes corresponding to each grapheme is too slow. In this case, no asso- ciations between the letters of the sequence can be formed. The idea here is that the formation of associations does not happen between purely visual letter forms but rather between graphemes. The associations between the graphemes are formed via associations between the phonemes for which the graphemes stand. Bower's proposal leaves unspecified whether any further processing takes place after pho- neme activation. Our own assumption is that the critical further step is the forma- tion of new phonological forms whereby the new phonological forms closely correspond to the grapheme sequences of the words. To illustrate, when German children encounter the grapheme sequence Kabel ("cable") for the spoken word IkabV, they learn the new orthography-related phonological word form Ikabell. This phonological form is generated when the grapheme sequence is phonologi- cally recoded, it is close enough to allow recognition, and, when retained, it sup- ports memory for the grapheme sequence. The phonological memory difficulties of our dyslexic children suggest that not only impaired speed in the generation of the new phonological forms is a problem but that an additionally problem is im- paired memory for the new phonological forms. This, then, is responsible for diffi- culties in establishing memory representations for the grapheme sequences of words. Our proposal is very close to Ehri's theorizing on the role of phonology in sight-word learning (e.g., Ehri, 1984, 1992). The only difference is that Ehri as- sumed that orthographic word representations alter existing phonological repre- sentations, whereas we assume that existing phonological representations may remain largely unaffected and that new additional phonological forms have to be learned to support orthographic representations.

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ACKNOWLEDGMENTS

Financial support for this research was provided by Austrian Science Foundation Grant PO991 1-HIS.

We gratefully acknowledge the help of Monika Fellner, Bianca Nicolussi, Simone Raab, and Brigit Stadler with data collection. This article profited from Heinz Wimmer's participation in the "Learning Disorders as a Barrier to Human De- velopment" workshops sponsored by theEuropean Commission (COST-Action 8).

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Manuscript received February 3, 1997 Final Revision received February 24, 1998 Accepted March 30, 1998

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