Cognitive Development of Lead Exposed Children from Ages 6 to 15 Years: An Application of Growth Curve Analysis

The effect of lead exposure on cognitive growth patterns was assessed in a longitudinal study of 196 children. Performances on tests of verbal comprehension and perceptual organization (Vocabulary & Block Design, Wechsler Intelligence Scales for Children) were measured at ages 6.5, 11 and 15 years. Growth curve analyses revealed that the quadratic model best described the relationship between test scores and age. Children with higher lead levels, as measured at age 15 years, demonstrated lower verbal comprehension scores over time and greater decline in their rate of Vocabulary development at age 15 years, as compared to children with lower lead levels. Lead exposure was not significantly associated with growth in perceptual organization test scores. Socioeconomic status and maternal intelligence were statistically significantly associated with growth patterns for both test scores, independent of the effects of lead. The findings suggest that lead negatively impacts the developmental progression of specific cognitive skills from childhood through adolescence.     

Cognitive development of lead exposed children from ages 6 to 15 years: an application of growth curve analysis.

The effect of lead exposure on cognitive growth patterns was assessed in a longitudinal study of 196 children. Performances on tests of verbal comprehension and perceptual organization (Vocabulary & Block Design, Wechsler Intelligence Scales for Children) were measured at ages 6.5, 11 and 15 years. Growth curve analyses revealed that the quadratic model best described the relationship between test scores and age. Children with higher lead levels, as measured at age 15 years, demonstrated lower verbal comprehension scores over time and greater decline in their rate of Vocabulary development at age 15 years, as compared to children with lower lead levels. Lead exposure was not significantly associated with growth in perceptual organization test scores. Socioeconomic status and maternal intelligence were statistically significantly associated with growth patterns for both test scores, independent of the effects of lead. The findings suggest that lead negatively impacts the developmental progression of specific cognitive skills from childhood through adolescence.     

Comparison between Gorham's Proverbs Test and the revised Shipley Institute of Living Scale for a black population

A total of 278 black women (183) and men (95) were administered the Gorham's Proverbs Test and the Shipley Institute of Living Scale (revised). This study compared Abstract scores on the Gorham's Proverbs Test with Vocabulary and Abstract scores on the Shipley Institute of Living Scale. The two tests were remarkably similar in terms of score distributions and susceptibility to the effects of age, perceived socioeconomic level during childhood, education, and perceived quality of education. Analysis also showed that abstract reasoning, as measured by these tests, is not free from the effects of vocabulary skills. Mean scores on both tests were within the range of mean scores previously reported in the literature.     

Heterosis doesn't cause the Flynn effect: a critical examination of Mingroni (2007)

Mingroni (2007) proposed that heterosis or hybrid vigor may be the principal driver of the Flynn effect--the tendency for IQ scores to increase at a rate of approximately 3 points per decade. This model was presented as a resolution to the IQ paradox--the observation that IQ scores have been increasing despite their high adult heritability--on the basis that substantial changes in IQ can only be accounted for by changes in underlying genetic factors. It is here argued that this model is predicated upon a misconception of the Flynn effect, which is most pronounced on the least g-loaded components of cognitive ability tests and is uncorrelated with genetic effects such as inbreeding depression scores (which are correlated with the g loadings of tests). Evidence supportive of the recently proposed life history model of the Flynn effect is presented. In the discussion, other theoretical objections to the heterosis model are also considered. On this basis, it is concluded that the Flynn effect is strongly entwined with developmental status and that heterosis cannot be its principal cause.     

Factor analysis of the Wechsler adult intelligence scale-revised (WAIS-R): An examination of the standardization sample

Orthogonal and oblique factor analyses were performed using the Wechsler Adult Intelligence Scale-Revised (WAIS-R) standardization sample (Wechsler, 1981). Using objective criteria, it was decided to retain two factors. Evidence for a strong general intelligence (g) factor was found from both the orthogonal and oblique rotations. Whereas the verbal IQ provided an acceptable estimate of the Verbal Comprehension factor, a purer measure was found in the form of a Verbal Comprehension Deviation Quotient containing only the Information, Vocabulary, Comprehension, and Similarities subtests. The performance IQ was found to be an inadequate measure of the Perceptual Organization factor. A Perceptual Organization Deviation Quotient, containing only the Block Design and Object Assembly subtests, was recommended as an effective alternative. Analysis of the variance components for each subtest at every age level revealed that a substantial proportion of subtests at a wide range of age levels evidence either high or intermediate levels of specific variance. These results are discussed in terms of interpreting individual subtest scores and patterns. Each of the study's major findings are compared with prior work done with the Wechsler Adult Intelligence Scale (WAIS) (Wechsler, 1955).     

Adult age and digit symbol substitution performance: a meta-analysis

This article reports the results of a meta-analysis of the effects of age, education, and estimated year of measurement on scores from the Wechsler Adult Intelligence Scale and the Wechsler Adult Intelligence Scale-Revised Digit Symbol Substitution Test. Analysis of effect sizes for age reported in 141 studies published between 1986 and 2002 indicated a mean standardized difference of -2.07. Age accounted for 86% of the variance in a regression model using age, education, and year submitted as predictors of Digit Symbol scores. There was no association between years of education or year submitted and Digit Symbol scores for younger adults or older adults.     

Rising verbal intelligence scores: implications for research and clinical practice

Evidence suggests that scores on various intelligence tests have been rising at a fast rate. To find out whether performance on the Wechsler Adult Intelligence Scale (WAIS) Vocabulary subtest has also been rising, the authors searched major psychology journals for investigations involving healthy younger and older adult participants and collected the reported WAIS Vocabulary scores. The meta-analysis shows that WAIS Vocabulary scores have been rising at the rate of 0.117/year (corresponding to 1.52 IQ points/decade) for younger adults and 0.367/year (corresponding to 4.79 IQ points/decade) for older adults.     

IQ and Scores on the Mini-Mental State Examination (MMSE)

The Mini-Mental State Examination (MMSE) and the Peabody Picture Vocabulary Test-Revised (PPVT-R) were administered to 217 Veterans Affairs (VA) Nursing Home patients, 104 of whom did not carry a diagnosis associated with brain impairment, and 113 who had a diagnosis associated with degenerative or cerebrovascular conditions. MMSE and IQ scores were significantly correlated in both groups, even controlling for the effects of education. It is suggested that although previous normative studies of the MMSE may provide good general clinical guidance, interpretation of “impaired” performance on the MMSE for those with IQ scores below 90 should be approached with caution. Average MMSE scores for Wechsler IQ classifications are provided.     

Secular declines in Spearman's g: some evidence from the United States

The Flynn Effect (J. Flynn, 1987) refers to the apparent increases in intelligence quotient (IQ) observed over the past few decades. A related phenomenon is that the variance in test scores accounted for by Spearman's g (C. Spearman, 1904) varies according to IQ level. That is, g accounts for less variance in high IQ groups than in low IQ groups. Spearman termed this variant aspect of g the "law of diminishing returns." This study extends prior research on the Flynn Effect and the law of diminishing returns by examining changes in the statistical importance of Spearman's g that may accompany secular increases in IQ. Based on the standardization data from the United States versions of the Wechsler scales (i.e., Wechsler Preschool and Primary Scales of Intelligence, D. Wechsler, 1967; Wechsler Intelligence Scale for Children, D. Wechsler, 1949; Wechsler Adult Intelligence Scale, D. Wechsler, 1955), this study indicated that, in most cases, the statistical significance of Spearman's g has indeed declined over the past several years. A. R. Jensen (1998) suggested that the components of the Flynn Effect warrant special investigation. The present study addresses this issue, in part by analyzing the Verbal and Performance subscales of the Wechsler scales. Additionally, this study further confirms the law of diminishing returns as applicable to different ages and time periods.     

Training referential communicative skills to individuals with autism spectrum disorder: a pilot study

The present study reports the effects of referential communication training in individuals formally diagnosed with autism spectrum disorder (ASD). Participants were 20 children with ASD (M age = 14.3 yr., SD = 4.2; 6 girls, 14 boys) in the role of speakers and 20 control children, who acted as listeners. They were all enrolled in mainstream compulsory education. Inclusion/exclusion criteria were defined according to the clinical diagnosis of ASD, the presence or absence of additional or associated disability, previous training in referential communication, and any drug treatment. Speakers were randomly assigned to one of two groups (trained vs untrained). Linguistic age, cognitive level and autistic symptoms were analyzed, respectively, with the Peabody Picture Vocabulary Test (PPVT), the Wechsler Intelligence Scale (WISC-R or WAIS-III), and the Autistic Behavior Checklist (ABC). Communicative abilities were analyzed through two indexes related to message complexity and self-regulation. The trained group was trained in referential communication tasks (task analysis, role taking, and task evaluation), while the untrained group took part in a communicative game but without any specific communicative training. The results showed that the complexity of emitted messages had improved statistically significantly in the trained group as an effect of training. Ecological referential communication is shown to be an appropriate paradigm for studying the communicative process and its products and could be used to develop and implement a training program focused on those skills in which individuals with ASD are most deficient.     

The Flynn effect and U.S. policies: the impact of rising IQ scores on American society via mental retardation diagnoses

Over the last century, IQ scores have been steadily rising, a phenomenon dubbed the Flynn effect. Because of the Flynn effect, IQ tests are periodically renormed, making them harder. Given that eligibility for mental retardation (MR) services relies heavily on IQ scores, renormed tests could have a significant impact on MR placements. In longitudinal IQ records from 9 sites around the country, students in the borderline and mild MR range lost an average of 5.6 points when retested on a renormed test and were more likely to be classified MR compared with peers retested on the same test. The magnitude of the effect is large and affects national policies on education, social security, the death penalty, and the military. This paper reports the perceptions of professionals as they relate to IQ score fluctuations in normal, borderline, and/or MR populations.     

Secular Declines in Spearman's g: Some Evidence from the United States

The Flynn Effect (J. Flynn, 1987) refers to the apparent increases in intelligence quotient (IQ) observed over the past few decades. A related phenomenon is that the variance in test scores accounted for by Spearman's g (C. Spearman, 1904) varies according to IQ level. That is, g accounts for less variance in high IQ groups than in low IQ groups. Spearman termed this variant aspect of g the “law of diminishing returns.” This study extends prior research on the Flynn Effect and the law of diminishing returns by examining changes in the statistical importance of Spearman's g that may accompany secular increases in IQ. Based on the standardization data from the United States versions of the Wechsler scales (i.e., Wechsler Preschool and Primary Scales of Intelligence, D. Wechsler, 1967; Wechsler Intelligence Scale for Children, D. Wechsler, 1949; Wechsler Adult Intelligence Scale, D. Wechsler, 1955), this study indicated that, in most cases, the statistical significance of Spearman's g has indeed declined over the past several years. A. R. Jensen (1998) suggested that the components of the Flynn Effect warrant special investigation. The present study addresses this issue, in part by analyzing the Verbal and Performance subscales of the Wechsler scales. Additionally, this study further confirms the law of diminishing returns as applicable to different ages and time periods.     

Diagnosing written language disabilities using the Woodcock-Johnson Tests of Educational Achievement-Revised and the Wechsler Individual Achievement Test

The writing portions of the Woodcock-Johnson Tests of Educational Achievement-Revised and the Wechsler Individual Achievement Test are often administered when establishing eligibility for special education services due to learning disabilities. The scores on these measures are typically regarded as equivalent although little is known about how scores on the two measures differ for the same students. Differences of only a few points, however, may affect eligibility for special education services. These tests were administered to 25 sixth grade students previously diagnosed with learning disabilities in written expression only. Students' Wechsler scores were consistently higher on the overall writing composite, while there was no difference in the mean scores on the language mechanics subtests. The WIAT Written Expression subtest mean, however, was significantly higher than the Woodcock-Johnson Writing Samples subtest mean. Use of the Wechsler test would be less likely to identify children for special education services in written expression when point discrepancy criteria are utilized for eligibility. Clinicians should be cognizant of the effect of the specific test chosen on eligibility outcome.     

Comparison of PPVT-R and WISC-R in a mild/moderate handicapped sample

The Peabody Picture Vocabulary Test-Revised, Form L was compared with the Wechsler Intelligence Scale for Children--Revised with a sample of 32 mild/moderate handicapped students (24 boys, 8 girls). Significant correlations were found between the WISC-R Full Scale IQ (.46) and the WISC-R Verbal IQ (.50) and the PPVT-R, but no significant correlation was found between the WISC-R Performance IQ and the PPVT-R (.34). Mean scores on the PPVT-R and WISC-R were significantly different.     

Use of the Peabody Picture Vocabulary Test with the educationally handicapped

Despite widespread use of the Peabody Picture Vocabulary Test (PPVT) as a measure of intelligence for educationally handicapped students, few studies have related PPVT scores of such students to their scores on the Wechsler Intelligence Scale for Children (WISC). Using 100 public school students consecutively referred for learning difficulties, their mean PPVT IQ (97.75) was found to be consistently and significantly higher than WISC Full Scale IQ (89.65), Verbal IQ (88.68), and Performance IQ (92.73). Correlations between the PPVT IQ and the WISC Full Scale, Verbal, and Performance IQs were .70, .69, and .54, respectively. A tabular summary of previous studies comparing PPVT and WISC IQs is included.     

IQ and scores on the Mini-Mental State Examination (MMSE): controlling for effort and education among geriatric inpatients

The Mini-Mental State Examination (MMSE) and the Peabody Picture Vocabulary Test, Third Edition (PPVT-III) were administered to 76 Extended Care Center inpatients of a Veterans Affairs Medical Center, 56 of whom did not carry a diagnosis associated with brain impairment, and 20 of whom had a diagnosis associated with degenerative or cerebrovascular conditions. MMSE and PPVT-III scores, the latter of which estimates verbal IQ, were significantly correlated in both groups, even when controlling for the effects of education. This correlation was attenuated, but remained significant, in the face of varying levels of patient effort. The findings of this study support earlier findings, which also suggest that interpretation of "impaired" performance on the MMSE for those with IQ scores below 90 should be interpreted with caution. Average MMSE scores for Wechsler IQ classifications are provided.     

Relationship between intelligence and vocabulary

This study explored the correlations of scores on the Wechsler Intelligence Scale for Children-III in screening language problems and scores on the three Comprehensive Receptive and Expressive Vocabulary Test subscales. Participants were 243 students ages 6 to 17 years in Grades K-11 who were identified as learning disabled, learning disabled with speech impairment, mentally retarded, and speech impaired. Analysis indicated strong correlations between the two measures, particularly between the CREVT General Vocabulary and WISC-III Verbal IQ (r = .80), WISC-III Verbal Comprehension Index (r =.83), and the Vocabulary subtest (r =.76). These results held across the grades. Supporting earlier studies of relationships of Verbal IQ and Receptive Vocabulary, correlations were lower between participants in Grades K through 2 than those in higher grades on the WISC-III Verbal IQ and the Receptive Vocabulary subtest. An analysis of the accuracy of the WISC-III for classifying students with language problems indicated improvement in classification over chance. These findings suggest that the WISC-III may be an effective screen for language problems.     

Feedback enhances the positive effects and reduces the negative effects of multiple-choice testing

Multiple-choice tests are used frequently in higher education without much consideration of the impact this form of assessment has on learning. Multiple-choice testing enhances retention of the material tested (the testing effect); however, unlike other tests, multiple-choice can also be detrimental because it exposes students to misinformation in the form of lures. The selection of lures can lead students to acquire false knowledge (Roediger & Marsh, 2005). The present research investigated whether feedback could be used to boost the positive effects and reduce the negative effects of multiple-choice testing. Subjects studied passages and then received a multiple-choice test with immediate feedback, delayed feedback, or no feedback. In comparison with the no-feedback condition, both immediate and delayed feedback increased the proportion of correct responses and reduced the proportion of intrusions (i.e., lure responses from the initial multiple-choice test) on a delayed cued recall test. Educators should provide feedback when using multiple-choice tests.     

Everyday memory performance across the life span: effects of age and noncognitive individual differences.

Gerontologists have long been concerned with the impact of individual-difference factors on memory. This study used a large sample (N = 2,495) of adult volunteers aged 18 to 90 years to determine if a set of individual-difference variables--vocabulary, education, depression, gender, marital status, and employment status--mediates the effects of aging on a wide range of laboratory-analogue tests of everyday memory. The data indicated that age was consistently the most significant predictor of memory performance, followed by vocabulary and gender. Vocabulary totally mediated age effects on a prose memory measure, and partial mediation of aging effects--primarily by vocabulary and gender--was observed on 5 other memory tests. These data suggest that when health samples of volunteers serve as research subjects, these individual differences can affect some memory test scores, but age remains the best overall predictor of memory performance.     

Effect of phonetics training on lingual awareness

This investigation assessed the effect of phonetics training on lingual awareness in normal adult speakers of English. The study also compared Trained subjects' scores from a study in 2000 by Lohman and Fucci to subjects' posttraining scores in this investigation. Subjects were 36 students (M age=19.7, SD=.7) enrolled in an undergraduate phonetics class. All passed a speech and hearing screening. A pretest-posttest design was used. Subjects received approximately 40 hours of phonetics training over a 10-wk. period. The lingual awareness test required subjects imitate seven syllables and respond to four multiple-choice questions about each syllable. Subjects were aided by a line drawing of the oral cavity. A significant improvement in lingual awareness was found following training. However, scores for only two phonemes (sh and k) improved significantly. No significant difference was found between posttest scores and scores from Lohman and Fucci's Trained group.