**3.2 Performance as a function of orthographical complexity**

#### **3.2.1 Orthographical performance by typically developing children**

Fig. 4 reports the typically developing children at each grade's mean correct response rate for reading achievement tests as a function of orthographical complexity. Error bars indicate standard deviations. There was significant difference between the mean correct response rate for orthographically complex characters and that for orthographically simple characters at Grade 2. The correct response rate was higher when the character was orthographically complex than when the character was orthographically less complex (Z=2.51, *p*<.01, *r*=.27). The sampling distribution was similar between the levels of orthographical complexity in other grades, according to Wilcoxon's signed rank test.

Assessing Orthographical and Phonological Impairments 77

Fig. 4. Correct response rate of reading as a function of orthographical complexity by

Fig. 5. Correct response rate of writing as a function of orthographical complexity by

Fig. 5 represents the typically developing children at each grade's mean correct response rate for writing achievement tests as a function of orthographical complexity. Error bars indicate standard deviations over sampling distribution. Statistical analysis revealed that the mean correct response rates were different between the levels of orthographic complexity at Grade 5 and at Grade 6. In both grades, the mean correct response rate was significantly lower when the character was orthographically complex than when the character was not (Z=-4.27, *p*<.0001, *r*=-0.43; Z=-2.29, *p*<.05, *r*=-0.23 respectively). There was no significant difference between the mean correct response rates at different orthographical levels in

typically developing children.

typically developing children.

Grade 2, 3 and 4.

Fig. 3. Overall Z scores of children with developmental disorders.

Fig. 3. Overall Z scores of children with developmental disorders.

Fig. 4. Correct response rate of reading as a function of orthographical complexity by typically developing children.

Fig. 5 represents the typically developing children at each grade's mean correct response rate for writing achievement tests as a function of orthographical complexity. Error bars indicate standard deviations over sampling distribution. Statistical analysis revealed that the mean correct response rates were different between the levels of orthographic complexity at Grade 5 and at Grade 6. In both grades, the mean correct response rate was significantly lower when the character was orthographically complex than when the character was not (Z=-4.27, *p*<.0001, *r*=-0.43; Z=-2.29, *p*<.05, *r*=-0.23 respectively). There was no significant difference between the mean correct response rates at different orthographical levels in Grade 2, 3 and 4.

Fig. 5. Correct response rate of writing as a function of orthographical complexity by typically developing children.

Assessing Orthographical and Phonological Impairments 79

From those graphs we see that, with both developmental disorders, Z scores for reading tended to be higher when the characters were orthographically complex, whereas Z scores for writing tended to show different patterns for participants with ADHD and for participants with dyslexia. With ADHD, the Z scores tended to decrease when the characters were orthographically complex. With dyslexia, on the other hand, such a tendency was not seen at all in Grade 3 and was less pronounced in Grade 4 and Grade 5,

Of particular importance in our study was whether the pattern of Z scores as a function of orthographical complexity can distinguish the cases when overall performance alone does not necessarily allow us to distinguish ADHD patients and dyslexics. The pattern of Z scores of Case 4 (dyslexic) and Case 13 (ADHD) in Grade 3 and that of Case 12 (dyslexic) and Case 17 (ADHD) in Grade 5 showed a different pattern in the writing achievement test. Those cases with ADHD showed that the Z scores decreased when the characters were

Fig. 7 reports the means of the correct response rate of reading achievement tests as a function of phonological complexity by typically developing children at each grade. Error bars indicate the standard deviations. The means of correct response for reading were significantly lower in Grade 4 and 6 when the character was phonological complex than when the character was not (Z=2.22, *p*<.05, r=.23; Z=3.18, *p*<.01, *r*=.32 respectively). There was no significant difference between the means of correct response at different orthographical levels in Grade 2, 3 and 5.

Fig. 7. Correct response rate of reading as a function of phonological complexity by typically

Fig. 8 reports the means of the correct response rate of spelling achievement tests as a function of phonological complexity by typically developing children at each grade. Error bars indicate standard deviations over sampling distribution. Statistical analysis by

orthographically complex, while this did not agree with the cases with dyslexics.

compared to the cases of ADHD patients in the same grades.

**3.3 Performance as function of phonological complexity** 

developing children.

**3.3.1 Phonological performance by typically developing children** 

#### **3.2.2 Orthographical performance by children with developmental disorders**

Fig. 6 represents the Z scores for the correct response rate of both dyslexics and ADHD patients for the reading and writing achievement tests as a function of orthographical complexity. The left side column shows the Z scores of the reading tests and the right side column shows those of the writing tests. Each row shows the Z scores of each grade. Filled data points in black represent the cases with dyslexia whereas unfilled data points represent the cases with ADHD.

Fig. 6. Z scores as a function of orthographical complexity by the children with developmental disorders.

Fig. 6 represents the Z scores for the correct response rate of both dyslexics and ADHD patients for the reading and writing achievement tests as a function of orthographical complexity. The left side column shows the Z scores of the reading tests and the right side column shows those of the writing tests. Each row shows the Z scores of each grade. Filled data points in black represent the cases with dyslexia whereas unfilled data points represent

**3.2.2 Orthographical performance by children with developmental disorders** 

Fig. 6. Z scores as a function of orthographical complexity by the children with

the cases with ADHD.

developmental disorders.

From those graphs we see that, with both developmental disorders, Z scores for reading tended to be higher when the characters were orthographically complex, whereas Z scores for writing tended to show different patterns for participants with ADHD and for participants with dyslexia. With ADHD, the Z scores tended to decrease when the characters were orthographically complex. With dyslexia, on the other hand, such a tendency was not seen at all in Grade 3 and was less pronounced in Grade 4 and Grade 5, compared to the cases of ADHD patients in the same grades.

Of particular importance in our study was whether the pattern of Z scores as a function of orthographical complexity can distinguish the cases when overall performance alone does not necessarily allow us to distinguish ADHD patients and dyslexics. The pattern of Z scores of Case 4 (dyslexic) and Case 13 (ADHD) in Grade 3 and that of Case 12 (dyslexic) and Case 17 (ADHD) in Grade 5 showed a different pattern in the writing achievement test. Those cases with ADHD showed that the Z scores decreased when the characters were orthographically complex, while this did not agree with the cases with dyslexics.

#### **3.3 Performance as function of phonological complexity**

#### **3.3.1 Phonological performance by typically developing children**

Fig. 7 reports the means of the correct response rate of reading achievement tests as a function of phonological complexity by typically developing children at each grade. Error bars indicate the standard deviations. The means of correct response for reading were significantly lower in Grade 4 and 6 when the character was phonological complex than when the character was not (Z=2.22, *p*<.05, r=.23; Z=3.18, *p*<.01, *r*=.32 respectively). There was no significant difference between the means of correct response at different orthographical levels in Grade 2, 3 and 5.

Fig. 7. Correct response rate of reading as a function of phonological complexity by typically developing children.

Fig. 8 reports the means of the correct response rate of spelling achievement tests as a function of phonological complexity by typically developing children at each grade. Error bars indicate standard deviations over sampling distribution. Statistical analysis by

Assessing Orthographical and Phonological Impairments 81

Fig. 9. Z scores as a function of phonological complexity by the children with developmental

disorders.

Friedman's test revealed that the mean score of correct response rate was different between the levels of orthographic complexity at Grade 4. The mean of correct response for writing was significantly lower when the character was phonological complex than when the character was not (Z=3.29, *p*<.001, *r*=.34). There was no significant difference between the means of correct response at different orthographical levels in Grade 2, 3, 5 and 6.

Fig. 8. Correct response rate of writing as a function of phonological complexity by typically developing children.

#### **3.3.2 Phonological performance by children with developmental disorders**

Fig. 9 represents the Z scores for the correct response rate of both dyslexics and ADHD patients for the reading and writing achievement tests as a function of phonological complexity. The left side column shows the Z scores of the reading tests and the right side column shows those of the writing tests. Each row shows the Z scores of each grade. Filled data points in black represent the cases with dyslexia whereas unfilled data points represent the cases with ADHD.

As seen in these graphs, the dyslexics tended to do worse in reading phonologically complex characters than in reading phonologically simple characters. Some of the children with ADHD showed a similar tendency, but many of them did not, and even those who did showed the tendency only to a lesser degree, compared to dyslexics. On the other hand, Z scores for writing seemed to be slightly higher for phonologically complex characters than for phonologically simple characters, both for dyslexics and for ADHD patients. This unexpected result might have been due to the control group scoring particularly low for phonologically complex characters.

Since dyslexics, but not ADHD patients, apparently tend to do worse in reading phonologically complex characters than in reading phonologically simple characters, we might be able to use the pattern of Z scores as a function of phonological complexity to differentiate dyslexics and ADHD patients, when overall performance alone does not allow us to. For instance, Case 4 (dyslexic) and Case 13 (ADHD) in Grade 3 showed different patterns of Z scores in the reading achievement test and could have been differentiated on that basis.

Friedman's test revealed that the mean score of correct response rate was different between the levels of orthographic complexity at Grade 4. The mean of correct response for writing was significantly lower when the character was phonological complex than when the character was not (Z=3.29, *p*<.001, *r*=.34). There was no significant difference between the

Fig. 8. Correct response rate of writing as a function of phonological complexity by typically

Fig. 9 represents the Z scores for the correct response rate of both dyslexics and ADHD patients for the reading and writing achievement tests as a function of phonological complexity. The left side column shows the Z scores of the reading tests and the right side column shows those of the writing tests. Each row shows the Z scores of each grade. Filled data points in black represent the cases with dyslexia whereas unfilled data points represent

As seen in these graphs, the dyslexics tended to do worse in reading phonologically complex characters than in reading phonologically simple characters. Some of the children with ADHD showed a similar tendency, but many of them did not, and even those who did showed the tendency only to a lesser degree, compared to dyslexics. On the other hand, Z scores for writing seemed to be slightly higher for phonologically complex characters than for phonologically simple characters, both for dyslexics and for ADHD patients. This unexpected result might have been due to the control group scoring particularly low for

Since dyslexics, but not ADHD patients, apparently tend to do worse in reading phonologically complex characters than in reading phonologically simple characters, we might be able to use the pattern of Z scores as a function of phonological complexity to differentiate dyslexics and ADHD patients, when overall performance alone does not allow us to. For instance, Case 4 (dyslexic) and Case 13 (ADHD) in Grade 3 showed different patterns of Z scores in the reading achievement test and could have been differentiated on that basis.

**3.3.2 Phonological performance by children with developmental disorders** 

developing children.

the cases with ADHD.

phonologically complex characters.

means of correct response at different orthographical levels in Grade 2, 3, 5 and 6.

Fig. 9. Z scores as a function of phonological complexity by the children with developmental disorders.

Assessing Orthographical and Phonological Impairments 83

Compared to children with ADHD, dyslexic children were found to have more trouble reading (if not writing) Chinese characters which have more than one possible pronunciation and are thus arguably phonologically more complex. This is consistent with the previous findings about dyslexia, but it is notable that ADHD patients did not show an analogous tendency. This observation indicates that the learning problems experienced by dyslexics and those experienced by ADHD patients are distinct from each other, possibly

Although our tests thus seem to have brought out some differences in performance between ADHD patients and dyslexics, there are obviously a number of issues that are left unresolved. For example, dyslexics' writing performance seemed not to be affected either by phonological complexity or by orthographical complexity. This leaves open the possibility that there are factors other than the above two factors that need to be taken into account, or that the sample size in this study was too small to allow us to detect an effect that is really there.

One purpose of our study was to facilitate intervention for children with ADHD or dyslexia by investigating the nature and magnitude of the learning problems faced by each group of children. The above results arguably have some implications in this regard. For instance, since children with ADHD were found to have difficulty in writing Chinese characters consisting of many strokes, it will probably be advisable, when we teach such children, to show them explicitly how to break visually complex characters into simpler components.

There are some limitations to this study that affect the generalizability of our results. First, the number of children at each grade was limited and consequently we could not ascertain the results using statistical tests. The use of our achievement tests in large groups of patients with developmental disorders in the future is likely to provide stronger evidence and further insight into the nature of learning problems among children with ADHD and dyslexia. Likewise, it will be possible to test the implications of this research more thoroughly if a longitudinal examination of children with developmental disorders is

Second, the control group was not a reading-level-matched group, but merely an agematched group with similar socioeconomic status. In order to mitigate the adverse effect of this limitation, we used material which includes only those Chinese characters that the children had learned at school more than a year prior to the experiment, so that we could ensure that the material would not be too difficult even for children with language-related problems, since some previous research has suggested that children with language-related problems may be delayed by as much as two years in a wide range of skills ((Kolb and Whishaw 2008; Wright and Zecker 2004) among others). However, future replications should use a reading-level-matched control group, as the failure to use such a control group in this study may have inflated the group difference between the children with

Nevertheless, in light of the fact that each condition affected some individuals in the same diagnostic groups similarly in comparison with the typically developing children, we

developmental disorders and the typically developing children.

reflecting the difference in innate cognitive abilities between the two groups

**4.3 Phonological performance** 

**4.4 Limitations and future directions** 

conducted.
