Intelligence Test Scores Research Articles

Reply to Commentators.

We thank Professors Brody (2007, this issue), Gottfredson (2007, this issue), and Steinberg and Grigorenko (2007, this issue) for their thoughtful comments. Hopefully our reply will further debate on this important topic. We said that so many definitions have been given that intelligence itself is a fuzzy (i.e., ill-defined) concept. Gottfredson claims this is not so, and offers what she presents as an agreedupon definition, based on statistical analyses of intelligence test scores. Sternberg and Grigorenko take us to task for not including emotionality and personal goals, which are part of Steinberg's notion of successful intelligence. Considering that these opposing criticisms come from well-established, knowledgeable investigators, we maintain our point. The definition of intelligence is fuzzy. One of the important steps in science is the creation of definitions that, in Plato's terms, carve nature at the joints. The distinction between acceleration and velocity was crucial to the advancement of physics. The study of intelligence would benefit by an analysis of clear definitions rather than claims that one or another group of investigators has discovered the right one. We believe that Gottfredson's emphasis on extant tests is too narrow, but that Steinberg and Grigorenko would cast such a broad net that it would make the study of intelligence unmanageable. We offered an intermediate position. We hope this matter will receive discussion in future papers. Brody is concerned that advances in understanding intelligence will depend upon the identification of new sources of evidence. We agree, but add that our concerns about design and interpretation will apply to studies using these new sources. The remaining criticisms by Gottfredson and Sternberg and Grigorenko can be divided into major issues and specific comments. We deal with the major issues first, beginning with Sternberg and Grigorenko, and then move to the specific points. Sternberg and Grigorenko argue that race is an invalid concept because (a) there are no infallible genetic, physical, or, for that matter, social indicators of race; (b) different societies vary in their categorization of racial groups; and (c) there is greater intraracial genetic variation than there is interracial variation.

Children Becoming More Intelligent: Can the Flynn Effect be Generalized to Other Child Intelligence Tests?

In this article, time effects on intelligence test scores have been investigated. In particular, we examined whether the “Flynn effect” is manifest in children from the middle and higher IQ distribution range, measured with a child intelligence test based on information processing principles—the Leiden Diagnostic Test. The test was administered to two independent groups of children—one tested recently, another tested 25 years ago. Analyses of the test scores showed that over time, children's IQ scores increased at least 15 points for those in the higher SES group and 8 points for those in the middle SES group. In a two-factor solution, scores on the Spatial-Analytic factor increased more than scores on the Verbal factor. Inspection of the three-factor solution showed that gains on the Spatial-Analytic factor were about .9 SD, on the Memory factor .8 SD, and on the Verbal factor .6 SD. The finding that performance or fluid abilities, measuring on-the-spot problem-solving, are more susceptible to change over time than crystallized abilities, measuring the results of learning in the past, is consistent with our hypothesis. However, the finding that aspects of children's memory are also susceptible to change over time was unexpected. It is hypothesized that the working memory system may have become more efficient over time because more information has tobe absorbedatamuch younger age, and coping with a stimulating environment may require a more efficient memory system.

The Parieto-Frontal Integration Theory (P-FIT) of intelligence: Converging neuroimaging evidence

"Is there a biology of intelligence which is characteristic of the normal human nervous system?" Here we review 37 modern neuroimaging studies in an attempt to address this question posed by Halstead (1947) as he and other icons of the last century endeavored to understand how brain and behavior are linked through the expression of intelligence and reason. Reviewing studies from functional (i.e., functional magnetic resonance imaging, positron emission tomography) and structural (i.e., magnetic resonance spectroscopy, diffusion tensor imaging, voxel-based morphometry) neuroimaging paradigms, we report a striking consensus suggesting that variations in a distributed network predict individual differences found on intelligence and reasoning tasks. We describe this network as the Parieto-Frontal Integration Theory (P-FIT). The P-FIT model includes, by Brodmann areas (BAs): the dorsolateral prefrontal cortex (BAs 6, 9, 10, 45, 46, 47), the inferior (BAs 39, 40) and superior (BA 7) parietal lobule, the anterior cingulate (BA 32), and regions within the temporal (BAs 21, 37) and occipital (BAs 18, 19) lobes. White matter regions (i.e., arcuate fasciculus) are also implicated. The P-FIT is examined in light of findings from human lesion studies, including missile wounds, frontal lobotomy/leukotomy, temporal lobectomy, and lesions resulting in damage to the language network (e.g., aphasia), as well as findings from imaging research identifying brain regions under significant genetic control. Overall, we conclude that modern neuroimaging techniques are beginning to articulate a biology of intelligence. We propose that the P-FIT provides a parsimonious account for many of the empirical observations, to date, which relate individual differences in intelligence test scores to variations in brain structure and function. Moreover, the model provides a framework for testing new hypotheses in future experimental designs.

Increases in the verbal and fluid cognitive abilities of disadvantaged children attending preschool in the Netherlands

Abstract The current longitudinal study examined the development of general cognitive abilities of 4–6-year-old children of low-income, ethnic-minority families in preschool over two and a half years by determining the changes in general, and in verbal and fluid cognitive abilities, relative to age norms, using an intelligence test. The results revealed significant increases over time, relative to age norms, in full scale and in both verbal and fluid intelligence test scores of disadvantaged children, with medium effect sizes. These gains in measured intelligence were moderated by children's home language and age. Children who gained most also profited most from their increased abilities with respect to emergent school skills. Gains in verbal intelligence predicted emergent school vocabulary, but gains in fluid intelligence did not. Overall, gains in fluid intelligence predicted emergent math skills, and gains in verbal intelligence predicted emergent math skills only among older children.

Intelligence test scores and birth order among young Norwegian men (conscripts) analyzed within and between families

The present paper reports the results of a within and between family analysis of the relation between birth order and intelligence. The material comprises more than a quarter of a million test scores for intellectual performance of Norwegian male conscripts recorded during 1984–2004. Conscripts, mostly 18–19 years of age, were born to women for whom almost complete reproductive histories were obtained. Women with single births only 1967–1998 and first birth 1967–1976 were selected for analyses. The grand mean stanine score for intellectual performance standardized for age and calendar year was 5.05 (SD = 1.80). The mean standardized score decreased with size of sibship and with higher birth orders in all sibship sizes. These patterns as well as the size of the difference between birth orders 1 and 3 were rather similar between and within families. Among 63 951 adjacent sibling pairs the mean standardized scores were 5.18 (95% confidence interval [CI]: 5.16, 5.19) for the elder and 4.93 (95% CI: 4.91, 4.94) for the younger brother. The difference in mean of standardized scores between adjacent siblings was − 0.251 (95% CI: − 0.270, − 0.231). The difference in mean standardized scores between brothers of adjacent birth orders increased with higher maternal level of education, was highest between brothers of married women, higher with paternal income and decreased with sibship size and longer spacing between births.

Four practical and conceptual assessment issues that evaluators should address in capital case mental retardation evaluations.

What unique assessment issues do evaluators face when conducting mental retardation evaluations in capital cases? This article describes 4 assessment issues and reports how 20 evaluators in 1 state have approached them: (a) What methods are appropriate for evaluating adaptive functioning in this context? (b) Should information about criminal behavior be used as evidence of adaptive functioning? (c) Should correctional officers serve as informants regarding adaptive behavior? and (d) How should the Flynn effect influence the interpretation of intelligence test scores? Implications for practice are that practitioners should expect to be asked about the relation between criminal behavior and adaptive functioning, must think carefully about the validity of tests of adaptive functioning for inmates, and must be knowledgeable about the current state of Flynn effect research.

Associations Between Childhood Intelligence and Hospital Admissions for Unintentional Injuries in Adulthood: The Aberdeen Children of the 1950s Cohort Study

We examined associations between childhood intelligence and hospital admissions for injuries in adulthood. Data were derived from a cohort study (=11103) involving individuals born in Aberdeen, Scotland, between 1950 and 1956. Overall, 1043 cohort members had at least 1 hospital admission resulting from an unintentional injury over 231152 person-years of risk. There were inverse linear associations between childhood intelligence assessed at the ages of 7, 9, and 11 years and having had a hospital admission stemming from an unintentional injury (gender-adjusted hazard ratio [HR] for a 1-standard-deviation increase in intelligence test score at age 7 years = 0.75; 95% confidence interval [CI]=0.70, 0.80). These associations were not markedly affected by adjustment for childhood socioeconomic status, maternal age or height, birthweight, or childhood growth. However, they were attenuated after adjustment for educational attainment (HR=0.85; 95% CI=0.78, 0.91). Childhood intelligence is related to hospital admissions for injuries in adulthood, and this relationship is partly explained by educational attainment. The association between childhood intelligence and injury may contribute to the association between childhood intelligence and premature mortality demonstrated in several studies.

Intelligence (IQ) Testing

1. Ellen B. Braaten, PhD* 2. Dennis Norman, EdD† 1. *Psychologist, Massachusetts General Hospital; Assistant Professor, Harvard Medical School, Boston, Mass 2. †Chief of Psychology, Massachusetts General Hospital; Associate Professor, Harvard Medical School, Boston, Mass After completing this article, readers should be able to: 1. Define intelligence quotient (IQ) and what constitutes the “normal” range of IQ scores. 2. Describe the predictive validity of intelligence test scores. 3. Discuss the factors that may influence performance on intelligence tests. 4. Recognize the relationship between variability observed in factor scores and the probability of the child having a learning or cognitive disability. 5. Describe how achievement tests are used in conjunction with IQ tests to determine eligibility for a learning disability. Intelligence tests assess a person’s mental abilities and compare them with the abilities of other people through the use of numerical scores. Although the term intelligence is used as if there is agreement on what it means, in reality there is much debate as to how this term should be and has been defined. For example, debate has surrounded whether intelligence should be considered an inherent cognitive capacity, an achieved level of performance, or a qualitative construct that cannot be measured. Psychologists have debated whether intelligence is learned or inherited, culturally specific or universal, and one ability or several abilities. While these debates are ongoing, evidence is increasing that traditional intelligence tests measure specific forms of cognitive ability that are predictive of school functioning, but do not measure the many forms of intelligence that are beyond these more specific skills, such as music, art, and interpersonal and intrapersonal abilities. (1) Despite these debates, most experts view intelligence as a person’s problem-solving abilities, such as adapting to the environment and having vocabulary skills, higher-order thinking (eg, decision making, reasoning skills, verbal and nonverbal problem-solving skills), memory, and mental speed. More specifically, for the purpose of this article, intelligence is discussed as it relates to a child’s score on the intelligence (IQ or “intelligence quotient”) tests that are used most commonly to measure …

Prevalence of myopia in Danish conscripts

This study aimed to determine the prevalence of myopia among Danish conscripts and compare the results with those from similar Danish studies carried out in 1882 and 1964. Furthermore, the relationships between myopia and educational level, ethnicity, intelligence (IQ), body mass index (BMI) and height were analysed. We carried out a cross-sectional study based on medical reports for 4681 male conscripts. The following data were collected from September to December 2004: age; place of birth; weight; height; power of spectacles or contact lenses; visual acuity; number of years at school (8-13 years); occupation; intelligence test (IQ test) score, and ethnicity. The prevalence of myopia (<or= - 0.5 D, spherical equivalent) was 12.8% (95% confidence interval [CI]+/- 0.96); the prevalence of high myopia (< - 6.5 D) was 0.3% (95% CI +/- 0.15). Myopes scored higher (45.3 [SD 9.4]) on IQ tests than emmetropes (41.4 [SD 10.4]) (p < 0.001) and had a higher educational level. No relationship was found between myopia and BMI, height or ethnicity. The study reports a significantly decreasing prevalence of low myopia among Danish conscripts in 2004 compared with 1964. Compared with the results from the 1882 study, the prevalence of low myopia seems stable. The prevalence of high myopia has decreased significantly since 1882 and has also tended to decrease from 1964. Number of years in education and IQ test score were related to myopia.

Genetics of intelligence

This article provides an overview of the biometric and molecular genetic studies of human psychometric intelligence. In the biometric research, special attention is given to the environmental and genetic contributions to specific and general cognitive ability differences, and how these differ from early childhood to old age. Special mention is also made of multivariate studies that examine the genetic correlation between intelligence test scores and their correlates such as processing speed, birth weight and brain size. After an overview of candidate gene associations with intelligence test scores, there is a discussion of whole-genome linkage and association studies, the first of which have only recently appeared.

Associations of Birth Defects with Adult Intellectual Performance, Disability and Mortality: Population-based Cohort Study

Infants born with birth defects have poorer outcomes in terms of mortality and disability, but the long-term intellectual outcome in children with birth defects is generally unknown. We assessed the long-term associations of various birth defects with mortality and disability, and evaluated whether high mortality and disability were reflected in impaired intellectual performance at age 18. In this nationwide cohort study, records of 9,186 males with and 384,384 without birth defects, registered in the Medical Birth Registry of Norway (1967-1979) were linked to the National Conscript Service (1984-1999). Mortality and disability before military draft, and intelligence test score at conscription were the main outcome measures. Males with birth defects had a relative risk for disability of 6.0 compared with males without defects. Disability was low within categories of birth defects associated with low mortality, and high within defect categories associated with high mortality. The relative risk for not being drafted was highest if maternal educational level was low. Heart defects and cleft palate were the only subgroups in which intellectual performance was lower after adjustment for maternal education, maternal age, marital status and birth order. In particular, intellectual performance was not impaired among those with multiple compared with single defects. We conclude that for the majority of birth defect categories in the present birth cohort, our hypothesis that intellectual performance would be impaired was not confirmed. Thus, there seems to be little reason to fear an adverse intellectual outcome in non-disabled surviving infants with birth defects.

African IQ and Mental Retardation

Rushton and Jensen (2005), in an extensive review of racial differences in intelligence test scores, assert that some part of the difference between blacks and whites in mean intelligence (IQ) scores is genetic in origin. They cite earlier reviews by Lynn (1991) and by Lynn and Vanhanen (2002), as well as several more recent studies, which are said to indicate that the mean IQ of sub-Saharan black Africans is about 70 - at the borderline of mental retardation. The present article reviews critically both the original studies and the ways in which the reviewers have described the findings of the studies.

Etiological Heterogeneity and Intelligence Test Scores in Patients with Schizophrenia

Previous research has indicated that patients with a family history of schizophrenia show a greater degree of cognitive and neuropsychological impairment than patients without a family history. We examined the neurocognitive performance, using the WAIS-R, of 51 patients with a family history (familial) and 103 patients without a family history (sporadic) to determine if differences exist that may help to explain the heterogeneous neuropsychological profile of the illness. The family history groups did not differ with respect to gender, diagnosis, ethnicity, age, age of onset, education or duration of illness. Multivariate analyses, covarying for age of onset and education, showed the sporadic group performed significantly better than the familial group on the digit symbol and object assembly subtests, with a trend level difference in overall performance IQ score. Additionally, we identified significant gender differences in favor of males for full scale and verbal IQ, the information, digit span, block design, and arithmetic subtests, and at a trend level, the picture assembly subtest. The family history group differences reflect relative dysfunction in visual attention and scanning, visuomotor control, and spatial processing and reasoning. Overall, the results suggest that sporadic patients have better perceptual-organizational skills and faster speed of processing.

GENERATIONAL CHANGES ON THE DRAW-A-MAN TEST: A COMPARISON OF BRAZILIAN URBAN AND RURAL CHILDREN TESTED IN 1930, 2002 AND 2004

Although gains in generational intelligence test scores have been widely demonstrated around the world, researchers still do not know what has caused them. The cognitive stimulation and nutritional hypotheses summarize the several diverse potential causes that have been considered. This article analyses data for a sample of 499 children tested in 1930 and one equivalent sample of 710 children tested 72 years later, the largest gap ever considered. Both samples comprised children aged between 7 and 11 who were assessed by the Draw-a-Man test in the city of Belo Horizonte, Brazil. Further, one additional sample of 132 children was assessed in 2004 in a rural area very similar in several diverse factors to the 1930 urban sample. The results are consistent with both the cognitive stimulation and the nutritional hypotheses.

Personality Disorders and Intelligence

Over 500 working adults completed two intelligence tests: the GMA (Graduate Management Assessment) and the WG (Watson-Glaser), a measure of the Big-Five personality traits (NEO-FFM), and a personality disorders measure (Hogan Development Survey). Regressing first the Big-Five personality traits, then the personality disorders, onto the two different measures of intelligence suggested evidence for the incremental validity of personality disorders, which in both studies accounted for an additional 5% of the variance. Results were slightly different in the two analyses though clearly obsessive-compulsiveness is negatively correlated with intelligence test scores.

Understanding Terminal Decline in Cognition and Risk of Death

There is new empirical evidence that the effects of impending death on cognition have been miscalculated because of neglect of the incidence of dropout and of practice gains during longitudinal studies. When these are taken into consideration, amounts and rates of cognitive declines preceding death and dropout are seen to be almost identical, and participants aged 49 to 93 years who neither dropout nor die show little or no decline during a 20-year longitudinal study. Practice effects are theoretically informative. Positive gains are greater for young and more intelligent participants and at all levels of intelligence and durations of practice; declines in scores of 10% or more between successive quadrennial test sessions are risk factors for mortality. Higher baseline intelligence test scores are also associated with reduced risk of mortality, even when demographics and socioeconomic advantage have been taken into consideration.

Balance marks cognitive changes in old age because it reflects global brain atrophy and cerebro-arterial blood-flow

In healthy old age biomarkers such as Balance robustly correlate with measures of mental abilities such as scores on tests of intelligence, reaction times and memory. A plausible explanation is that balance reflects general physiological fitness and so also neurophysiological integrity, but direct evidence is lacking. Brain scans measured age-associated loss of brain volume and cerebro-arterial blood flow (CBf) in 69 volunteers aged from 62 to 81 years who also took the Tinetti Balance test battery, 3 tests of fluid intelligence, 3 tests of decision speed and a memory test. Balance, but not atrophy or CBf, predicted intelligence test scores. Balance, atrophy, and CBf all independently predicted speed and memory scores but, after variance in atrophy and CBf had been considered, predictions from Balance were no longer significant. It appears that in these tests Balance marks cognitive performance in old age because it reflects gross age-related neurophysiological changes.

Low Intelligence Test Scores in 18 Year Old Men and Risk of Suicide: Cohort Study

Low Intelligence Test Scores in 18 Year Old Men and Risk of Suicide: Cohort Study

Stereotype Threat and Group Differences in Test Performance: A Question of Measurement Invariance.

Studies into the effects of stereotype threat (ST) on test performance have shed new light on race and sex differences in achievement and intelligence test scores. In this article, the authors relate ST theory to the psychometric concept of measurement invariance and show that ST effects may be viewed as a source of measurement bias. As such, ST effects are detectable by means of multi-group confirmatory factor analysis. This enables research into the generalizability of ST effects to real-life or high-stakes testing. The modeling approach is described in detail and applied to 3 experiments in which the amount of ST for minorities and women was manipulated. Results indicate that ST results in measurement bias of intelligence and mathematics tests.

Childhood intelligence in relation to adult coronary heart disease and stroke risk: evidence from a Danish birth cohort study

While recent studies have reported an inverse relation between childhood intelligence test scores and all-cause mortality in later life, the link with disease-specific outcomes has been rarely examined. Furthermore, the potential confounding effect of birthweight and childhood social circumstances is unknown. We investigated the relation of childhood intelligence with coronary heart disease (CHD) and stroke risk in a cohort of 6910 men born in 1953 in the Copenhagen area of Denmark. Events were ascertained from 1978 to 2000 using a cause-of-death register and hospital discharge records. There were 150 CHD (19 fatal; 131 non-fatal) and 93 stroke (4 fatal; 89 non-fatal) events during follow-up into mid-life. Childhood intelligence was inversely related to CHD with the highest rate apparent in adults with low childhood test scores (HR(lowest vs. highest quartile), 2.70; 95% confidence interval: 1.60, 4.57; P(trend) = 0.0001). After adjustment for paternal social class and birthweight, this association was attenuated only marginally. There was little evidence of a IQ-stroke relationship. The cognitive characteristics captured by IQ testing in the present study, such as communication and problem solving ability, appear to be associated with risk of CHD. Health promotion specialists and clinical practitioners may wish to consider these skills in their interactions with the general public. Replication of these results using studies which hold data on intelligence and socio-economic position across the life course is required.