The IQs of children with ADHD are normally distributed

The purpose of this investigation was to determine whether or not attention-deficit/hyperactivity disorder (ADHD)-when there was an absence of reading problems-was associated with having a high IQ. The vocabulary and block design short forms of the Wechsler Intelligence Scale for Children-Third Edition were administered to 63 children with ADHD, 69 children with reading difficulties (RD), and 68 children with comorbid ADHD + RD. Results indicated that the distributions of estimated Full Scale IQs (FSIQ) for each of the three groups of children did not differ significantly from a normal distribution, with the majority of children (more than 50%) in each group scoring in the average range. The percentage of children with ADHD who scored in the above-average range for FSIQ was not significantly higher than the percentages of children in the other two groups. No significant group differences emerged for estimated FSIQ, vocabulary, or block design. It was concluded that children with ADHD are no more likely to have an above-average IQ than are other children.     

Substance use, substance abuse, and LD among adolescents with a childhood history of ADHD

A clinic-referred sample of 109 children with attention-deficit/hyperactivity disorder (ADHD) was followed into adolescence for the ascertainment of alcohol and other drug use and abuse. Learning disability (reading or math) in childhood was examined as a predictor of adolescent substance use and substance use disorder for alcohol and marijuana. No statistically significant group differences for children with LD versus those without LD emerged even after using different methods to compute LD. IQ/achievement discrepancy scores were similarly not predictive of later use or abuse. However, children with ADHD who had higher IQs and higher levels of academic achievement in childhood were more likely to try cigarettes, to smoke daily, and to have their first drink of alcohol or first cigarette at an early age. Children with ADHD who had higher reading achievement scores were less likely to have later alcohol use disorder. Although these findings are necessarily preliminary, due to the small number of children interviewed, the pattern of results suggests that level of cognitive functioning--rather than discrepancy between IQ and achievement--is important for the prediction of later substance use and abuse, at least in this clinic-referred sample of children with ADHD. Further, different mechanisms of risk related to cognitive functioning may be operating for experimentation with legal drugs such as alcohol and tobacco, regular cigarette smoking, and problematic alcohol use.     

WISC-III profiles for children with and without learning disabilities

The degree of WISC-III intersubtest scatter was normal and similar for 66 children with LD and 51 children without LD, but the pattern of scores differed. In the 8- to 16-year-old sample, children with LD scored lower on the Freedom from Distractibility Index relative to FSIQ than children without LD. This difference was found in both the ADHD and nonADHD subgroups, suggesting that children with LD may have an attention deficit even if they do not meet the diagnostic criteria for ADHD. The CAD profile was evident in the mean scores for both the LD/ADHD and LD/nonADHD subgroups, but it was not found among the lowest subtest scores for any of the nonLD subgroups. Though WISC-III profile types were apparent in LD group data, only a minority of individual children with LD actually had these profiles. In the 6- and 7-year-old group, children with and without LD were indistinguishable on the WISC-III, which may reflect the difficulty of ruling out LD at this young age. © 1998 John Wiley & Sons, Inc.     

Paint-by-Number Teachers and Cookie-Cutter Students: The Unintended Effects of High-Stakes Testing on the Education of Gifted Students

This study examined the utility of the Gifted Composite (GC) formula derived from selected subtests on the Stanford-Binet Intelligence Scales, Fifth Edition (SB5) for evaluating intellectual giftedness. A sample of 52 children were administered both the SB5 and Woodcock-Johnson Tests of Achievement, Third Edition (WJ-III ACH). The ability of the Full-Scale IQ (FSIQ) and the GC to predict reading and math achievement were compared. Though both the FSIQ and GC significantly predicted standardized achievement test scores, the FSIQ explained more of the variance. Sequential regression analyses suggested that the SB5 factor scores preformed differently in their contribution of unique variance to the predictions. The inclusion of working memory scores in the calculation of the FSIQ appears to account for the difference in predictions between the FSIQ and GC for reading but not math skills.     

The relative roles of IQ and cognitive processes in reading disability

The purpose of the present study was to explore the relative roles of IQ and cognitive processes in reading performance. A sample of 443 Spanish children (264 male, 179 female) ranging in age from 7 to 13 years were classified into four groups according to IQ scores (<80, 80–90, 90–110, >110) and reading disabled (RD) and normally achieving readers (NR) were compared. The findings indicate that IQ scores were not related to the differences between children with RD and NR. We found that reading‐related cognitive deficits do differentiate between RD and NR children. Therefore, IQ scores do not make a significant contribution to our understanding of reading disability.     

The intellectual profile of abused and neglected children in the Philippines: An analysis of SB5 IQ scores of sexually abused,physically abused and neglected children

Child abuse and neglect have been associated with cognitive deficits, among other effects on child development. This study explores the prediction that child abuse and neglect has an impact on Stanford-Binet Intelligence Scales 5th Edition (SB5) IQ scores, in relation to gender, age and type of abuse experienced. 300 children with experiences of abuse and neglect were included in the study, comprising 100 sexually abused, 100 physically abused and 100 neglected children. Overall, all scores on the SB5 were found to be significantly lower than the minimum average scores on the test. Verbal IQ (VIQ) scores were likewise found to be significantly lower than Nonverbal IQ (NVIQ) scores. Full Scale IQ (FSIQ) scores did not reveal heterogeneity when gender was factored in. Age and type of abuse (with a moderate effect size) on the other hand, showed significant differences among groups. Statistical analyses of SB5 Factor Index Scores revealed that abused children, in general, have significantly higher Visual-Spatial Processing (VS) and Quantitative Reasoning (QR) scores and lower scores in Knowledge (KN). There was a large effect size found in such an analysis. Age (with a large effect size), gender and type of abuse (with moderate effect sizes) give significant variations to this obtained profile.     

Early Histories of School‐Aged Children With Attention‐Deficit/ Hyperactivity Disorder

In a prospective study of developmental outcomes in relation to early‐life otitis media, behavioral, cognitive, and language measures were administered to a large, diverse sample of children at 2, 3, 4, 6, and 9–11 years of age (N = 741). At 9–11 years of age, 9% of the children were categorized as having attention‐deficit/hyperactivity disorder (ADHD) based on parent report. Compared to the non‐ADHD group, the ADHD group had higher (i.e., less favorable) scores on parent and teacher versions of the Child Behavior Checklist at all ages. Children in the ADHD group also had lower scores on cognitive and receptive language measures in preschool. The findings support the concept that ADHD is a cognitive as well as a behavioral disorder.     

The relationship between IQ and reading disabilities in English-speaking Canadian and Spanish children

This study was designed to examine the role of intelligence (IQ) in the definition of reading disabilities (RD) in languages with different orthographic systems. A sample of 94 Spanish children and 157 English-speaking Canadian children with RD was classified into four groups on the basis of IQ scores from the Wechsler Intelligence Scale for Children-Revised (< 80; 81-90; 91-109; 110-140). We examined the reading and spelling skills of Canadian and Spanish children as a function of Full Scale, Verbal, and Performance IQ scores. Significant differences between the languages were found when reading performance was analyzed as a function of Verbal IQ scores, in that there were some differences between the groups of Canadian children with RD but not between the groups of Spanish children. The Canadian children with Verbal IQ scores < 80 demonstrated relatively lower performance in reading and spelling skills than the Canadian groups with higher IQ scores. There were differences in reading tasks as a function of Performance IQ in English but not in Spanish. The differences in the role of IQ as a function of orthographic systems may relate to the greater significance of visual-orthographic as opposed to phonological processing in English.     

Attention deficit disorder and specific reading disability: separate but often overlapping disorders

Within a large (N = 182) heterogeneous sample of clinic-referred children with DSM-III-diagnosed attention deficit disorder (ADD), three behavioral subgroups were identified via cluster analysis of teacher ratings: 40% of the children had ADD with hyperactivity (ADDH), 30% had ADD with hyperactivity and aggressivity (ADDHA), and 31% had ADD without hyperactivity or aggressivity. Proportionally more girls were in the ADD-only subgroup. Over half the sample (n = 94) were poor readers, with 82 meeting discrepancy criteria for specific reading disability (RD). Proportionately more boys than girls met the RD criteria (9.2:1.0), whereas the sex ratio of males to females for the whole sample was 5.1 to 1.0. Focusing just on white males, the three behavioral subgroups were significantly different on convergent validity measures, such as other teacher ratings, parent ratings, and interview-elicited ratings of externalizing behavior, but were not different on such divergent validity measures as IQ and achievement scores, self-ratings, and laboratory performance tasks. Boys in the ADD sample who did not meet criteria for RD had significantly higher IQs than those who did, but subgroups with and without RD still differed significantly on WRAT-R reading and spelling scores with IQ covaried out. Both groups with and without RD could be differentiated from a control group on laboratory measures of sustained attention and impulse control. Methylphenidate benefited all subgroups equally, whether RD or not, and whether given a low (0.3 mg/kg) or high (0.6 mg/kg) dose.     

Adults with reading disabilities: converting a meta-analysis to practice

This article reviews the results of a meta-analysis of the experimental published literature that compares the academic, cognitive, and behavioral performance of adults with reading disabilities (RD) with average achieving adult readers. The meta-analysis shows that deficits independent of the classification measures emerged for adults with RD on measures of vocabulary, math, spelling, and specific cognitive process related to naming speed, phonological processing, and verbal memory. The results also showed that adults with high verbal IQs (scores > 100) but low word recognition standard scores (< 90) yielded greater deficits related to their average reading counterparts when compared to studies that included adults with RD with verbal IQ and reading scores in the same low range. Implications of the findings related to assessment and intervention are discussed.     

Evidence for unexpected weaknesses in learning in children with attention-deficit/hyperactivity disorder without reading disabilities

This study examined the mechanisms underlying verbal learning in children with and without attention-deficit/hyperactivity disorder (ADHD), none of whom had reading disabilities. Children with ADHD were compared to typically developing children on both process and product scores from the California Verbal Learning Test for Children. The findings indicated that children with ADHD initially learned the same number of words as controls but showed weaknesses recalling the words after delays, suggesting that children with ADHD are less efficient learners. Regardless of ADHD status, boys and girls performed differently. Boys used semantic clustering less frequently and recalled fewer words from the middle region of the list than girls; girls also outperformed boys in terms of overall performance, despite lower verbal IQ scores. These findings show that children with ADHD can exhibit unexpected weaknesses in learning even without a formal learning disability. Gender differences in verbal learning are also illustrated.     

Occurrence and pattern of impaired reading and written language in children with attention deficit disorders

The purpose of this study was to investigate the occurrence and severity of reading, spelling, and written language impairment in children clinically referred for Attention Deficit Hyperactivity Disorder (ADHD). Specific questions involved 1) whether ADD subgroups with and without hyperactivity differ in reading, spelling, and written language achievement, 2) whether age and gender interact with ADD sub-group class to affect reading/written language achievement, and 3) whether prevalence of impaired reading/written language in these subgroups is consistent with previous reports in heterogeneous samples. Subjects were 115 ADD children aged 6-12 who were subclassified as ADD + H(72 percent) and ADD - H(28 percent) by objective teacher ratings. Dependent measures included tests of single word recognition and vocabulary, word attack, contextual comprehension, written spelling, written sentence construction, and writing fluency, in addition to a structured behavioral observation, during which aspects of inattention and motor activity were coded. A large fraction of this sample met public school LD criteria (54 percent), and achievement on most measures was globally poorer than the respective test normative groups. The ADD + H subgroup showed significantly poorer word attack skills, while the subgroups did not significantly differ from each other on other reading/written language measures. However, 17 percent of the total ADD sample were ≥ 1.5 SD below the mean in total reading achievement, and 29 percent were ≥ 1.5 SD below the mean on measures of written spelling/language. Gender X age interactions, indicating poorer performance in the middle age group of females, were likely related to lower IQ.     

Differential genetic etiology of reading disability as a function of IQ

To test the hypothesis that the genetic etiology of reading disability differs as a function of IQ, composite reading performance data from 223 pairs of identical twins and 169 pairs of same-gender fraternal twins in which at least one member of each pair was classified with reading disability were subjected to multiple regression analysis (DeFries & Fulker, 1985, 1988). In the total sample, heritability of the group deficit in reading performance (h(g)2) was .58 (+/- .08). However, when the basic regression model was fitted separately to data from twin pairs with average Wechsler (1974, 1981) full scale IQ scores below 100 or 100 and above, resulting estimates of h(g)2 were .43 and .72, respectively, a significant difference (p < or = .03, one-tailed). The results of fitting extended regression models to reading performance and continuous IQ data provide evidence that the genetic etiology of reading disability differs as a linear function of IQ (p < or = .007, one-tailed). These results suggest that IQ is relevant for the diagnosis of reading disability and that environmental influences may be more salient as a cause of reading difficulties in children with lower IQ scores.     

IQ and neuropsychological predictors of academic achievement

Word reading and math computation scores were predicted from Wechsler Abbreviated Scale of Intelligence Full Scale IQ, 10 neuropsychological tests, and parent attention deficit hyperactivity disorder (ADHD) ratings in 214 general population elementary school children. IQ was the best single predictor of achievement. In addition, Digit Span contributed significantly to reading prediction, and the Developmental Test of Visual-Motor Integration (VMI) and Coding contributed to math prediction. The remaining neuropsychological test scores did not significantly improve achievement prediction. Exploratory factor analysis yielded a general ability factor (comprising the four IQ subtests, Digit Span, VMI, reading, and math), five factors made up solely of subtests from single measures (Wisconsin Card Sorting Test, Stroop Color and Word Test, Gordon Diagnostic System, California Verbal Learning Test, and ADHD ratings), a factor consisting of Grooved Pegboard Test and Coding, and a factor consisting of Symbol Search and Animal Naming Test.     

Correlates of Academic Overachievement,Nondiscrepant Achievement,and Learning Disability in ADHD,Autism, and General Population Samples

ABSTRACT

Little is known about the characteristics of academic overachievers, children whose achievement significantly exceeds IQ. Correlates of overachievement (achievement test scores ≥ 1 SD above IQ), nondiscrepant achievement, and learning disability (LD; achievement ≥ 1 SD below IQ) were analyzed in 1,543 children (739 ADHD, 285 autism, and 519 general population), 6–16 years of age. Significant correlates of the reading and math achievement groups were diagnosis (autism greatest overachievement, ADHD greatest LD), IQ (lowest in overachievers and highest in LD), and Working Memory scores relative to the child’s IQ (close to or exceeding IQ in overachievers and lower than IQ in LD). Demographics (age, sex, race, and parent occupation) and parent and teacher ratings of psychopathology (e.g., behavior problems, anxiety, and depression) and personality characteristics (e.g., motivation and self-confidence) did not contribute significantly more to predicting overachievement and LD beyond that explained by IQ, diagnosis, and working memory. These findings suggest an underlying neurobiological etiology for both overachievement and LD.     

An investigation of cognitive skills and behavior in high ability students

The purpose of this study was to investigate the cognitive and behavioral profiles of high ability students. Performance on measures of verbal and visuo-spatial working memory and general ability (vocabulary and block design) was compared across the following groups: high, average, and low ability students. The behavioral profile of high ability students was also compared with those with a clinical diagnosis of ADHD. The working memory performance was superior in the high ability students compared to the low and average ability groups, though the relationship between working memory and IQ weakens as a function of increasing ability. The findings are discussed in light of Spearman's law of diminishing returns. The behavioral profile of this group indicates similar features in some respects to those with a clinical diagnosis of ADHD, however, underlying explanations may differ and should be taken into consideration in future research on dual needs in high ability students.     

Predictors of ability-achievement discrepancies in children referred for psychoeducational evaluation

The present study evaluated a school district's psychoeducational screening program to determine the best predictors of two difference score variables: (a) WISC-R FSIQ – PIAT reading recognition score and (b) WISC-R FSIQ – PIAT math score. The study also investigated the merit of using scores from a group-administered achievement test (CAT) as predictors. Subjects were 61 first through fifth graders initially referred for testing from 1982–1984. Multiple regression analyses indicated: (a) for reading, the SIQ score and the PPVT-R – CAT reading difference score were significant predictors, together accounting for 27% of the variance, and (b) for math, the PPVT-R score accounted for 28% of the variance, with additional variables producing nonsignificant increments. Results suggest that CAT scores may prove useful predictors when combined with screening IQ tests to form difference scores.     

The Cognitive and Behavioral Characteristics of Children With Low Working Memory

This study explored the cognitive and behavioral profiles of children with working memory impairments. In an initial screening of 3,189 five- to eleven-year-olds, 308 were identified as having very low working memory scores. Cognitive skills (IQ, vocabulary, reading, and math), classroom behavior, and self-esteem were assessed. The majority of the children struggled in the learning measures and verbal ability. They also obtained atypically high ratings of cognitive problems/inattentive symptoms and were judged to have short attention spans, high levels of distractibility, problems in monitoring the quality of their work, and difficulties in generating new solutions to problems. These data provide rich new information on the cognitive and behavioral profiles that characterize children with low working memory.     

Pathsways to school achievement in very preterm and full term children

Individual differences in academic success were investigated in a geographically defined whole-population sample of very preterm children with a gestational age of less than 32 weeks or a birth weight of less than 1500 gm. The sample consisted of 264 very preterm children (75.6% of German-speaking survivors) and 264 controls matched for gender, socioeconomic status, marital status and age of mother, who were studied from birth. The present analyses focused on the impact of cognitive skills assessed at ages 6 and 8 on academic success at the age 13. IQ scores, prereading skills, reading, spelling, and math performance assessed during the last kindergarten year and again at the end of Grade 2 were used as predictors of academic success in early adolescence. Differences between very pretern children and controls in cognitive abilities already observed in earlier assessments remained stable over time, with controls on average performing more than half a standard deviation above the level of preterm children. Preterm children also performed poorer on the literacy measures and indicators of math performance. Multivariate and causal modeling revealed different prediction patterns for the two groups. Whereas IQ was particularly important for the prediction of academic success in the pre-term sample, general IQ was less relevant for the prediction of academic success in the control group. When subgroups of at-risk children were formed according to birth weight categories, we found that school problems were most pronounced for children with extremely low birth weight (1000 gm and less).     

Differences between WISC‐R and WISC‐III performance scale among children with ADHD

Reviews involving the Wechsler Scales for children suggest that Full Scale IQ scores on the Wechsler Intelligence Scale for Children, Third Edition, average 5 to 6 points lower than scores on the second edition of the scale [WISC‐R, Wechsler, D. (1974). Zimmerman & Woo‐Sam, 1997], with the differences distributed disproportionately over subtests, i.e., with larger discrepancies found within the Performance Scale (Wechsler, 1991). Changes on the revised subtests of the WISC‐III Performance Scale may place children with ADHD at a disadvantage compared to their performance on analogous WISC‐R subtests. We examined IQ test performance in 122 unmedicated children with ADHD (61 given the WISC‐R, 61 given the WISC‐III), and 46 children from a healthy, comparison group (23 given the WISC‐R, 23 given the WISC‐III). The ADHD and comparison group samples were matched for sex and for Verbal IQ between WISC‐R and WISC‐III. Children with ADHD had significantly lower Performance IQ on WISC‐III compared to the WISC‐R, with the Picture Arrangement subtest showing the most significant difference. In contrast, there were no significant differences between the WISC‐R and WISC‐III cohorts on Performance IQ or any Performance subtests among the comparison group. These findings highlight the importance of examining the comparability of ability test revisions among clinical and non‐clinical populations, and will be especially salient when the WISC‐III is revised. © 2003 Wiley Periodicals, Inc. Psychol Schs 40: 331–340, 2003.