Wechsler Intelligence Scale For Children-Revised Research Articles

Sex differences on the WISC-R in Mauritius

Sex differences on the WISC-R (Wechsler Intelligence Scale for Children-Revised) are examined in a sample of 1258 11 year olds in Mauritius. Boys obtained a significantly higher Full Scale IQ by 5.8 IQ points. Boys obtained a higher Performance IQ by 6.5 IQ points and a higher Verbal IQ by 1.0 IQ points. On the subtests, girls obtained a significantly higher mean on Coding while boys obtained significantly higher means on Similarities, Picture Completion, Block Design, Object Assembly and Mazes. There was no significant sex difference on Digit Span. Two methods were adopted for determining whether boys had an advantage on Spearman's g. First, calculated from the first principal component of a principal components analysis, boys had an advantage on Spearman's g of 6.15 IQ points. Second, using the method of entering the sex difference on each of the subtests as point-biserial correlations, including these in the full matrix of subtest correlations for factor analysis and examining the factor loading of sex on g produced a correlation between sex and g of .224, the equivalent of a sex difference of 6.9 IQ points. Thus the sex difference on the Full Scale IQ was found to be a good approximate measure of the difference in g. The pattern of sex differences in Mauritius is compared with that in eight other countries and found to be generally similar, although the boys' advantage is greater in Mauritius than elsewhere. The variance in boys is slightly greater than in girls, but is only significant for Block Design.

Quality of Life and Psychomotor Development After Surgical Treatment of Hydrocephalus

The purpose of this report is to analyse the long-term outcome in hydrocephalic children treated by shunt insertion, in particular their psycho-intellectual development and quality of life. We studied 46 patients aged 3 - 21, who had been operated on in the Department of Paediatric Surgery of the Medical University of Bialystok between 1982 - 2000 and had had ventriculo-peritoneal shunts inserted during their first year of life. Data from anamnesis and medical documentation were analysed. Age-appropriate psychomotor development and IQ tests were carried out: Wechsler Intelligence Scale for Children, Revised (WISC-R) (for children between the ages of 6 and 16), Wechsler Adult Intelligence Scale, Revised (WAIS-R PL) (for adults), Brunet-Lezine psychometric scale (early childhood), and Terman-Merril intelligence scale (children younger than 3). The final IQs were above 90 in 30 % of children, between 70 and 90 in 24 %, between 50 and 70 in 26 %, and lower than 50 in 20 %. 69 % of patients presented with neurological deficits and visual or auditory deficits were found in 22 %. Integration into normal schools was possible for 58.7 % of the children, one of whom is now a second year medical student. A relationship between shunt malfunction and the children's development was observed. An essential aspect of caring for hydrocephalic children is their rehabilitation and integration into society. Early physical rehabilitation, stimulation of psychological development, and continued monitoring by a paediatric surgeon to ensure proper functioning of the shunts will improve the independence of such children in their families and among their peers.

Children With Congenital Hypothyroidism and Their Siblings: Do They Really Differ?

Although favorable outcome is typically described in follow-up studies of children with congenital hypothyroidism (CH) identified by newborn screening, IQ reductions and persistent cognitive deficits are still reported. These findings are accounted for by disease and treatment variables as well as methodologic factors including choice of comparison group. Although siblings are ideal because they control for genetic and environmental influences, by definition they have different ages when tested, which can also introduce bias. Because we followed children with CH and their siblings over an extended period of time, there were a number of occasions when both groups were tested at the same age. The purpose of this study was to compare the results of children with CH and their unaffected siblings at the same age and with the same test. The sample consisted of 42 children with CH detected between 1975 and 1985 and their 42 siblings, all of whom were tested with the McCarthy or Wechsler Intelligence Scale for Children-Revised (WISC-R) intelligence tests. Nineteen pairs of children were evaluated at 6 years with the McCarthy, and 30 pairs of children were evaluated at 7 or 9 years with the WISC-R. Recorded for children with CH were disease etiology, bone age and thyroxine levels at diagnosis, age at onset of treatment, and starting dosage of levothyroxine. Paired t tests revealed that the CH group scored lower than siblings by 8.1 IQ points on the McCarthy and 6.2 points on the WISC-R. Factors contributing to the size of the CH-sibling IQ difference were (1) the etiology of hypothyroidism, reflecting the larger differences by those with athyreosis or an ectopic gland than dyshormonogenesis, and (2) the starting dosage of levothyroxine, with those initially treated with >or=8.2 microg/kg per day having smaller CH-sibling differences than those given lower starting doses. There were no effects of bone age, thyroxine levels at diagnosis, or age at treatment onset. Children with CH treated early in life due to newborn screening may have reduced IQ relative to siblings.

Behavioural, academic and neuropsychological profile of normally gifted Neurofibromatosis type 1 children

In the present study the neuropsychological, academic and social-emotional profiles were examined in Neurofibromatosis type 1 (NF1) children. 17 NF1 children (ages 7-11) with NF1 without serious medical problems and with a full scale IQ (FSIQ) above 70. Wechsler Intelligence Scale for Children-Revised (WISC-R), academic tests and an exhaustive neuropsychological test battery were administered in all children. Parents and teachers filled out the Child Behavioural Checklist (CBCL) and Teacher Report Form (TRF), respectively, the NF1 children the Experienced Competence Scale for Children (ECSC). Nearly 50% (8/17) of the children showed learning disabilities, when corrected for IQ in the academic evaluations. Isolated impaired literacy skills, particularly spelling problems, were most frequent (4/8), whereas a pure arithmetic learning disability was rare (1/8). Three children presented both learning disabilities. Results on academic and neuropsychological tests did not fit the well-known types of learning disabilities -- nonverbal learning disability (NLD) and dyslexia. Nearly all NF1 children showed visual perceptual and executive dysfunctions. In this study, teachers more frequently reported behavioural problems in NF1 children than parents, as opposed to literature data in a general population. The correspondence of the perception of internalizing problems between the children and teachers was greater than between children and their parents. No correlation was found between the performances on the WISC-R, specific neuropsychological results, academic performances and behavioural problems. The Deficiency in Attention, Motor and Perception (DAMP) concept seems most appropriate in order to describe the neuropsychological deficits and their repercussions on behavioural and academic performances seen in NF1 children.

Relationship Between Physical, Environmental and Sociodemographic Factors and School Performance in Primary Schoolchildren

Poor primary school performance is a risk factor for low high-school and university graduation, as well as poverty in later life. In this case-control study, the relation between a variety of physical, environmental and sociodemographic factors, and primary school performance was investigated. Grade one students with good and poor school achievement, from different socioeconomic levels were studied. A questionnaire about the sociodemographic characteristics and child's medical history, together with a Child Behavior Checklist, was filled out by parents. Physical examination, visual and hearing screening were performed. Blood count and blood lead levels were determined. Wechsler Intelligence Scale for Children-Revised (WISC-R) was performed to determine the IQ. A total of 177 students participated in the study. Stepwise logistic regression revealed an independent positive relation between duration of study (OR, 2.69; Cl, 1.19-6.05; p=0.016), maternal education (OR, 1.47; Cl, 1.14-1.87; p=0.002), full scale score of WISC-R (OR, 1.08; Cl, 1.03-1.3; p=0.002) and school performance. Multinomial logistic regression revealed that the risk of having a below average full scale WISC-R score was higher among children having a hearing loss, uncorrected vision loss, heating house with stove, cigarette smoking of both parents, and low paternal education (less than 8 years). The chance of having an above average full scale WISC-R score was lower among children whose either parent smoked cigarettes, height-for-age percentile was below 10, and maternal education was less than 8 years. Policies for increasing male and female education, growth monitoring, appropriate feeding (breastfeeding and weaning), well-baby and child followup and clean environment (indoor and outdoor) will not only promote the physical health but also promote the cognitive development of the new generations.

Maternal Phenylketonuria Collaborative Study (MPKUCS)—The 'outliers'

Analysis of outcome data from 305 of the 414 offspring from the Maternal Phenylketonuria Collaborative Study (MPKUCS), plus 70 control offspring, revealed significant deficits in the IQ (intelligence quotient), as measured by the Wechsler Intelligence Scale for Children--Revised (WISC-R), when maternal metabolic control during pregnancy was delayed and/or inadequate. There were, however, 23 'outliers' (7.5% of the 305) in which the offspring's intellectual IQ was worse (n =10) or better (n =13) than expected. The aim of this study was to determine whether collection parameters were incomplete or whether these subjects were true biological variants influenced by other undetected factors or, perhaps, by modifier genes. Among the 10 offspring whose intellectual functioning was worse than expected, additional complications were uncovered that could explain the poor outcome. Four of the 13 offspring with higher than expected IQ had mothers with mild variants of PKU in which the insult to the fetus would not be expected to be as profound. For the other nine offspring whose intellectual performance was better than expected, there was no explanation, based on the parameters studied. We hypothesize that modifier genes will, at times, protect the fetus despite high maternal concentrations of phenylalanine. Not all offspring from the same (untreated) PKU mother may be similarly affected. Finding the source of these modifiers might effect the treatment of MPKU.

Intellectual Development of Children Born of Mothers who Fasted in Ramadan during Pregnancy

The long-term effects of Ramadan fasting during pregnancy on the brain development of the fetus are still not clear. The aim of this study was to evaluate the effects of maternal fasting during Ramadan on the intelligence quotient of their progeny. A historical cohort study was conducted on 191 children aged between 4 to 13 years, 98 whose mothers fasted throughout Ramadan when they were pregnant with their children (case group) and 93 children whose mothers did not fast (control group). The children were selected from 15 schools via a questionnaire filled out by their mothers. Detailed demographic, medical history, and socioeconomic status data were collected by interviewing the mothers. All children aged between 6 to 13 were administered the Wechsler Intelligence Scale for Children-Revised (WISC-R), and those aged between 4 to 6 were administered Wechsler Preschool and Primary Scales of Intelligence (WPPSI), and intelligence quotient was estimated. Cases included 47 boys and 51 girls aged 8.5+/-2.5 years and controls included 44 boys and 49 girls aged 8.7+/-2.5 years. There were no significant differences in sex and age between two groups. Among background and confounder variables, the percentage of Caesarean section and the duration of breast-feeding were significantly different between case and control groups; 29% Caesarean section in cases vs. 45% in controls (p < 0.05) and 17.2+/-9 months breast-feeding for cases vs. 14.5+/-9 months for controls (p < 0.05). There were no significant differences in socioeconomic status of families between the groups whereas socioeconomic status accounted for approximately 17% of the variances in the average of full-scale intelligence quotient scores. Adjusted mean and standard deviation of full-scale intelligence quotient scores, performance and verbal, were 111+/-10, 109+/-11 and 110+/-11 for the case group and 112+/-10, 110+/-11 and 110+/-11 for the control group respectively. No significant differences were observed between the IQ scores of the two groups. Fasting during gestation did not adversely affect IQ of children whose mothers had fasted during Ramadan while being pregnant.

Academic achievement among formerly homeless adolescents and their continuously housed peers

This study examined the school experiences and academic achievement of 46 adolescents in families who experienced homelessness and 87 permanently housed adolescents whose families received public assistance. Measures taken after the homeless students were rehoused showed that both groups valued school highly and were similar in cognitive abilities assessed with the similarities subtest of the Wechsler Intelligence Scale for Children—Revised (WISC-R). Formerly homeless students had more school mobility, more grade retention, and worse school experiences by mother report and lower plans for post-secondary education by self-report. Both groups scored poorly on standardized tests of academic achievement. Homelessness was associated with further declines in achievement during the period of maximal residential disruption, but did not have effects 5 years later.

Academic achievement among formerly homeless adolescents and their continuously housed peers

This study examined the school experiences and academic achievement of 46 adolescents in families who experienced homelessness and 87 permanently housed adolescents whose families received public assistance. Measures taken after the homeless students were rehoused showed that both groups valued school highly and were similar in cognitive abilities assessed with the similarities subtest of the Wechsler Intelligence Scale for Children—Revised (WISC-R). Formerly homeless students had more school mobility, more grade retention, and worse school experiences by mother report and lower plans for post-secondary education by self-report. Both groups scored poorly on standardized tests of academic achievement. Homelessness was associated with further declines in achievement during the period of maximal residential disruption, but did not have effects 5 years later.

Sex differences in developmental reading disability: new findings from 4 epidemiological studies.

An influential article published in 1990 claimed that the increased rate of reading disability in boys was a consequence of referral bias. To summarize the history of research on sex differences in reading disability and to provide new evidence from 4 independent epidemiological studies about the nature, extent, and significance of sex differences in reading disability. The Dunedin Multidisciplinary Health and Development Study comprised 989 individuals (52.1% male) in a cohort born between April 1972 and March 1973 in Dunedin, New Zealand, and followed up from age 3 years; reading performance and IQ were assessed at ages 7, 9, and 11 years using the Burt Word Reading Test and the Wechsler Intelligence Scale for Children-Revised (WISC-R), respectively. The Christchurch Health and Development Study comprised 895 individuals (50% male) in a prospectively studied cohort born in the Christchurch, New Zealand, region during a 4-month period in 1977; reading performance and IQ were assessed at ages 8 to 10 years using the Burt Word Reading Test and the WISC-R. The Office for National Statistics (ONS) Study comprised a UK nationally representative sample of 5752 children (50.1% male) aged 9 to 15 years in 1999; reading was assessed on the British Ability Scales II and IQ on the British Picture Vocabulary Scales II. The Environmental Risk Longitudinal Twin Study (E-Risk) comprised 2163 twin children from England and Wales (49.1% male) identified at birth in 1994 and 1995 and included administration of the Test of Word Reading Efficiency at age 7 years and the Wechsler Preschool and Primary Scale of Intelligence-Revised as a test of IQ at age 5 years. Reading performance by sex in the lowest 15% of the distribution for all 4 studies, with and without taking IQ into account. In all 4 studies, the rates of reading disability were significantly higher in boys. For non-IQ-referenced reading disability: Dunedin study, 21.6% in boys vs 7.9% in girls (odds ratio [OR], 3.19; 95% confidence interval [CI], 2.15-4.17); Christchurch study, 20.6% in boys vs 9.8% in girls (OR, 2.38; 95% CI, 1.62-3.50); ONS study, 17.6% in boys vs 13.0% in girls (OR, 1.43; 95% CI, 1.23-1.65); and E-Risk, 18.0% in boys vs 13.0% in girls (OR, 1.39; 95% CI, 1.04-1.86). The rates for IQ-referenced reading disabilities were similar. Reading disabilities are clearly more frequent in boys than in girls.

Sex differences in performance over 7 years on the Wechsler Intelligence Scale for Children--Revised among adults with intellectual disability.

The aim of this study was to explore changes related to sex differences on the Wechsler Intelligence Scale for Children - Revised (WISC-R) subtest performance over a 7-year interval in middle-aged adults with intellectual disability (ID). Cognitive sex differences have been extensively studied in the general population, but there are few reports concerning individuals with ID. Sex differences are of current relevance to actively debated issues such as cognitive changes during menopause and risk for Alzheimer's disease. Given that hormonal effects on cognition have been observed in the general population, particularly in areas such as visuospatial processing, and individuals with Down's syndrome (DS) have been reported to be hormonally and reproductively atypical, we analysed our data to allow for the possibility of an aetiology-specific profile of sex differences for these adults. The WISC-R subtests were administered in a longitudinal study, as part of a more comprehensive test battery, at least twice within 7 years. Participants were 18 females with ID without DS [age at first test time (time 1): mean = 40.5; IQ: mean = 59.3], 10 males with ID without DS (age at time 1: mean = 42.4; IQ: mean = 59.4), 21 females with DS (age at time 1: mean = 37.9; IQ: mean = 51.6), and 21 males with DS (age at time 1: mean = 40.3; IQ: mean = 54.3). All participants were in the mild to moderate range of ID and were displaying no changes suggestive of early dementia. Females, regardless of aetiology of ID, exhibited a robust superiority on the coding subtest, which parallels the widely reported difference among adults in the general population. Additionally, there was a decline in overall performance during the 7-year study interval, particularly on the verbal subscale subtests, but there was no evidence of sex-differentiated decline. There were also marginal sex by aetiology interactions on the object assembly and block design subtests, suggesting that males with unspecified ID might perform better than their female peers, but among adults with DS, females might do better than males. This study supports the presence of cognitive sex differences in the population with ID as indicated by female superiority on the WISC-R coding subtest. Extending this observation to adults with ID has implications for explanations of female advantage on this task, which now have to account for its presence among individuals with a broader range of intellectual capabilities, more atypical developmental histories and more varied genotypes than previously considered. Trends towards sex by aetiology interactions on the two visuoconstructive subtests, while marginal, were sufficient to warrant continued consideration of the idea of a distinct profile of sex differences for adults with DS and to justify looking at the effects of sex separately within different aetiologies of ID.

Does the Flynn Effect Differ by IQ Level in Samples of Students Classified as Learning Disabled?

This research examined scores from two learning-disabled (LD) samples for evidence of the Flynn Effect (FE; Flynn, 1999) to determine (a) whether the FE was evident, and (b) if the magnitude of the FE differed on IQ scores at varying levels of intelligence. Sample 1 consisted of 40 children who were administered the Woodcock-Johnson Tests of Cognitive Ability-Revised (WJ-R Cog) and the Woodcock-Johnson Tests of Cognitive Ability-Ill (WJ-III Cog) approximately 8 weeks apart. Sample 2 consisted of triennial test data for 169 students who were tested once with the Wechsler Intelligence Scale for Children-Revised (WISC-R) and 3 years later with the Wechsler Intelligence Scale for Children-Third Edition (WISC-III). After an initial analysis for the overall FE, Samples 1 and 2 were each divided into IQ level groups (e.g., 91-105) and analyzed accordingly. Results for Sample 1 (W-J) indicated that the 2+ point observed IQ change was not significant for this relatively small sample, although it appeared to be consistent with the direction and degree predicted by the FE (Flynn, 1984). Results for Sample 2 (WISC) indicated a significant IQ change consistent with the FE. Neither sample exhibited statistically significant differences for FE by IQ level. However, consistent with previous research, observed differences increased from lower to higher IQ levels. Consequently, this research cannot rule out the possibility that a child's IQ level influences the degree to which the FE is apparent.

Brief report: Cross-cultural replication of an anomalous psychometric pattern in children with type 1 diabetes.

To replicate an anomalous psychometric profile previously documented in children with Type 1 diabetes living in the mainland United States with a cross-cultural sample selected from Puerto Rico. Ninety-three Spanish-speaking children (M age = 12.8 years) with Type 1 diabetes living in Puerto Rico were administered the Puerto Rican version of the Wechsler Intelligence Scale for Children-Revised (WISC-R). The factor structure of the Puerto Rican sample's WISC-R was then compared to that of a United States sample (n = 95) in which an anomalous factor structure in children with diabetes was first documented. As in the United States sample, a four-factor IQ structure was obtained. Instead of the traditional three-factor structure of the WISC-R, the Perceptual Organization factor split into a Spatial Conceptual factor and an anomalous Visual Discrimination factor. Results support previous findings and suggest anomalies in the psychometric profiles of children with Type 1 diabetes. Cross-cultural replication of the anomalous IQ factor structure, and atypical visual discrimination, suggests that differences are illness-related, and consideration may therefore be warranted when administering some subtests of the Wechsler scales to children with Type 1 diabetes.

Neurocognitive functioning in children with type-1 diabetes with and without episodes of severe hypoglycaemia.

Previous studies have shown that recurrent severe hypoglycaemia can cause long-term cognitive impairment in children with type-1 diabetes, but the results are controversial, possibly due to the heterogeneity of samples and lack of comprehensive neuropsychological assessments of children. The aim of this study was to assess the effects of diabetes and severe hypoglycaemia on the neurocognitive functioning of children with a standardized, wide age-range neuropsychological test battery designed for the assessment of children. Eleven children with diabetes and a history of severe hypoglycaemia, 10 children with diabetes without a history of severe hypoglycaemia, and 10 healthy control children (a total of 31 children: 14 males and 17 females, age range 5 years 6 months to 11 years 11 months, mean 9 years 4 months, SD 1 year 11 months) were studied using the Wechsler Intelligence Scale for Children-Revised (WISC-R) and the NEPSY, a Developmental Neuropsychological Assessment. The NEPSY assessed development in attention and executive functions, language, sensorimotor functions, visuospatial processing, and learning and memory. Children with a history of severe hypoglycaemia had more neuropsychological impairments, more learning difficulties (as reported by parents), and needed more part-time special education than those in the other groups. Significant differences were found in verbal short-term memory and phonological processing. Results suggest that severe hypoglycaemia is a risk factor for learning due to deficits in auditory-verbal functioning.

Behavioral disorders in pediatric epilepsy: unmet psychiatric need.

This study examined the relation between psychiatric diagnosis and mental health services in children with epilepsy and the associated demographic, cognitive, linguistic, behavioral, and seizure-related variables. The Kiddie Schedule for Affective Disorders and Schizophrenia (K-SADS), the Child Behavior Checklist, the Test of Language Development, and the Wechsler Intelligence Scale for Children-Revised (WISC-R) were administered to 114 children, aged 5 to 16 years, with either complex partial seizures (CPS) or primary generalized with absence (PGE, petit mal). A Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) diagnosis and information regarding mental health services were derived from the K-SADS. Although approximately 60% of the subjects had a DSM-IV psychiatric diagnosis, >60% received no mental health treatment. Absence of mental health care was associated with younger age, less parental education, limited number of antiepileptic drugs (AEDs; i.e., one or none), and higher verbal IQ. In addition, children with PGE and a single psychiatric diagnosis were less likely to have a history of mental health treatment. This is the first study to demonstrate unmet mental health need in a large sample of children with CPS and PGE. The study's findings suggest that parents and clinicians should be aware of the mental health needs of children with epilepsy, particularly if they have one or more of the identified risk factors.

Neurocognitive functioning in children with type‐1 diabetes with and without episodes of severe hypoglycaemia

Previous studies have shown that recurrent severe hypoglycaemia can cause long‐term cognitive impairment in children with type‐1 diabetes, but the results are controversial, possibly due to the heterogeneity of samples and lack of comprehensive neuropsychological assessments of children. The aim of this study was to assess the effects of diabetes and severe hypoglycaemia on the neurocognitive functioning of children with a standardized, wide age‐range neuropsychological test battery designed for the assessment of children. Eleven children with diabetes and a history of severe hypoglycaemia, 10 children with diabetes without a history of severe hypoglycaemia, and 10 healthy control children (a total of 31 children: 14 males and 17 females, age range 5 years 6 months to 11 years 11 months, mean 9 years 4 months, SD 1 year 11 months) were studied using the Wechsler Intelligence Scale for Children‐Revised (WISC‐R) and the NEPSY, a Developmental Neuropsychological Assessment. The NEPSY assessed development in attention and executive functions, language, sensorimotor functions, visuospatial processing, and learning and memory. Children with a history of severe hypoglycaemia had more neuropsychological impairments, more learning difficulties (as reported by parents), and needed more part‐time special education than those in the other groups. Significant differences were found in verbal short‐term memory and phonological processing. Results suggest that severe hypoglycaemia is a risk factor for learning due to deficits in auditory‐verbal functioning.

Cognitive Functioning as Measured by the WISC-R

Patterns of performance on the Wechsler Intelligence Scale for Children-Revised (WISC-R) have been proposed as useful tools for the identification of children with learning disabilities (LD). However, most of the studies of WISC-R patterns in children with LD have been plagued by the lack of a typically achieving comparison group, by failure to measure individual patterns, and by the lack of a precise definition of LD. In an attempt to address these flaws and to assess the presence of patterns of performance on the WISC-R, we examined data from 121 children with typical achievement (TA), 143 children with reading disabilities (RD), and 100 children with a specific arithmetic disability (AD), ages 6 to 16 years. The results indicated that the RD and AD groups had significantly lower scores than the TA group on all the Verbal IQ subtests. Many of the children with AD and RD showed a significant difference between Verbal and Performance IQ scores, but so did many of the typically achieving children. Although there were some children with LD who showed the predicted patterns, typically, 65% or more of the children with LD did not. Furthermore, a proportion of the TA group-generally not significantly smaller than that of the RD and AD groups-showed discrepancy patterns as well. Our results indicate that the patterns of performance on intelligence tests are not reliable enough for the diagnosis of LD in individual children. Therefore, it might be more profitable to base the detection of an individual's LD on patterns of achievement test scores.

African–White IQ differences from Zimbabwe on the Wechsler Intelligence Scale for Children-Revised are mainly on the g factor

African–White differences on the sub-tests of the Wechsler Intelligence Scale for Children-Revised (WISC-R) in Zimbabwe are like the Black–White differences in the US in being positively associated with the sub-tests' g loadings ( g being the general factor of intelligence). Published means and S.D.s for 204 12- to 14-year-old Zimbabweans on 10 WISC-R sub-tests were compared against those for 1868 White Americans. A principal factor analysis of the correlation matrix from the US standardization sample for Whites, along with the point-biserial correlation of African–White standardized differences, showed that fully 77% of the between-group race variance was attributable to a single source, namely g.

Can Excess Bilirubin Levels Cause Learning Difficulties?

Objective. Jaundice due to excessive unconjugated bilirubin, is observed in approximately 60% of term infants during the first week of life and in approximately 80% of preterm infants. We hypothesize that excessive unconjugated bilirubin levels may result in learning difficulties because of damage to the thalamus, the hippocampus, the central areas of the cerebellum, the basal ganglia area, and in particular because of damage to the astrocytes associated with neurons of the basal ganglia area. We suggest that these infants appear to recover fully from jaundice but present with learning difficulties later when exposed to an educational environment. Methods. IQ scores of a group of children ( n =22) with learning difficulties (due to excessively high levels of unconjugated bilirubin) are also discussed. The Senior South African Individual Scale - Revised (SSAIS-R) was administered to determine the intellectual functioning of the subjects. The SSAIS-R has been standardised for South African children between the ages of 7 years 0 months and 16 years 11 months with Afrikaans or English as mother tongue. The SSAIS-R is a point scale (deviation IQ scale) and is based on research data derived from the Wechsler Intelligence Scale for Children - Revised (WISC-R). Observed verbal and non-verbal subtest scores, along with standardized total scores are summarized using descriptive statistics and Hotelling's T-test and individual verbal and non-verbal subtest scores are discussed. Results. Results indicate that these children have lowered verbal abilities. The majority of subjects revealed impaired short-term and long-term memory. Based on the literature kernicterus and high levels of unconjugated bilirubin affects the basal ganglia and the formation of astrocytes, and possibly also the hippocampus, the thalamus and central parts of the cerebellum. The hippocampus has important functions in the storing of new information in forms that can be used in long-term memory. Damage to the left region of the hippocampus impairs verbal memory in all its modalities. Conclusion. Impaired formation of astrocytes associated with high levels of unconjugated bilirubin should be considered as an etiological factor in poor memory. We recommend that pediatricians should suggest early screening procedures to infants at risk. With early screening for possible deficiencies of attention, memory, and visual-motor integration functioning as well as intervention programs the learning difficulties can be addressed and remediation started earlier in life

The causal factor underlying the correlation between psychometric g and scholastic performance

Structural equation models were fitted to covariances among 9 Cognitive Abilities Test (CAT) variables, 11 Wechsler Intelligence Scale for Children—Revised (WISC-R) subtest scores, and 3 Metropolitan Achievement Test (MAT) scaled scores, administered to a sample of 532 primary school children who participated in the Western Reserve Twin Project. The models were designed to test the hypothesis that factors representing basic cognitive processes, extracted from the nine CAT variables, were the main causal determinants for the observed correlation between psychometric g and scholastic performance, which were represented, respectively, by a general factor extracted from the WISC-R and a factor from the MAT. Structural relations between the CAT factors as the primary independent variables, psychometric g as a secondary independent variable, and scholastic performance as the dependent variables were estimated, and the R 2 change indicating the higher-order shared variability between g and scholastic performance was evaluated. After the influence of a CAT general factor was controlled, the WISC-R general factor accounted for about 6% of the variability in the MAT scholastic factor, as opposed to as much as 30% of the zero-order variability shared by the two variables. The results were not seriously affected by the exclusion of nonchronometric measures of the cognitive tasks from the model, suggesting that individual differences in mental speed are a main causal factor underlying the observed correlation between general intelligence and scholastic performance in children between the ages of 6 and 13.