Intelligence Test Scores Research Articles

Improvement in Intelligence Test Scores From 6 to 10 Years in Children of Teenage Mothers

This study investigates change in IQ scores among 290 children born to teenage mothers and identifies social, economic, and environmental variables that may be associated with change in intelligence test performance. The children of 290 teenage mothers (72% African-American and 28% European American) were assessed with the Stanford-Binet Intelligence Scale-4th Edition at ages 6 and 10. The mean composite score at age 6 was 84.8 and 91.2 at age 10, an improvement of 6.4 points. Significant cross-sectional predictors at both ages 6 and 10 of higher Stanford-Binet Intelligence Scale scores were maternal cognitive ability, school grade, white ethnicity, and caregiver education. Having more children in the household significantly predicted lower Stanford-Binet Intelligence Scale scores at age 6. Higher satisfaction with maternal social support predicted higher Stanford-Binet Intelligence Scale scores at age 10. Change in IQ scores was not related to maternal socioeconomic status, social support, home environment, ethnicity, or family interactions. Custodial stability was associated with an improvement in IQ scores, whereas increase in caregiver depression was related to decline in IQ scores. Our findings suggest that improvement in IQ scores of offspring of teenage mothers may be related to stability of maternal custody. More research is needed to determine the impact of the maturation of adolescent mothers' parenting and the role of early education on improvement in cognitive abilities.

Examining the Impact of Integrating Physical Activity on Fluid Intelligence and Academic Performance in an Elementary School Setting: A Preliminary Investigation

To examine the impact of integrating physical activity with elementary curricula on fluid intelligence and academic achievement. A random sample of 3rd grade teachers integrated physical activity into their core curricula approximately 30 minutes a day, 3 days a week from January 2008 to April 2008. Noninvasive fluid intelligence cognitive measures were used along with State-mandated academic achievement tests. Experimental Group children averaged close to 1200 pedometer steps per integration day, thus averaging 3600 steps per week. Children in the Experimental Group performed significantly better on the SPM Fluid Intelligence Test. Children in the Experimental Group also performed significantly better on the Social Studies State mandated academic achievement test. Experimental Group children also received higher scores on the English/Language Arts, Math and Science achievements tests, but were not statistically significant compared with Control Group children. Children classified in Fitnessgram's Healthy Fitness Zone for BMI earned lower scores on many of the SPM Fluid Intelligence components. This investigation provides evidence that movement can influence fluid intelligence and should be considered to promote cognitive development of elementary-age children. Equally compelling were the differences in SPM Fluid Intelligence Test scores for children who were distinguished by Fitnessgram's BMI cut points.

Large-Scale Medical Resequencing for X-Linked Mental Retardation

Severe intellectual disability (ID),1 commonly referred to as mental retardation (MR), comprises a large collection of clinical conditions whose associated phenotypes include substantially below-average intelligence test scores and limited abilities in socially adaptive behaviors, such as communication, self-care, social interaction, and school functioning. ID/MR affects 1%–3% of the worldwide population with variable severity, is a frequent cause of pediatric, genetic, neurologic, and developmental medicine referrals, and poses huge social and economic burdens. Genetic factors, such as trisomy 21 in Down syndrome, and environmental risk factors, such as fetal alcohol syndrome, contribute to the pathogenesis of ID/MR. Although the genetic causes are heterogeneous and complex, a 30%–40% excess of males vs females and the existence in many families of an evident X-linked inheritance pattern suggest a major role for inactivating mutations in X-chromosome genes. The notion is that these mutations cause ID/MR predominantly in males, in whom, unlike females, there is no second X chromosome present to complement the defect and thereby inhibit its phenotypic expression. Consequently, a variety of molecular genetic strategies have been applied to the X chromosome, including candidate gene analysis, linkage mapping followed by location cloning, and precise delineation of chromosomal anomalies (balanced translocation, inversion, and microdeletion/duplication). These efforts have led to the discovery of a trinucleotide expansion in the 5′ untranslated region of the FMR1 2 (fragile X mental retardation 1) gene as the cause of fragile X syndrome, the most frequent form of X-linked ID/MR, and mutations in approximately 90 other genes in rarer families (1)(2). Because known genes account for less than half of the >200 delineated X-linked ID/MR conditions (http://xlmr.interfree.it/home.htm), many novel X-linked genetic factors have yet to be identified. To address this issue, Tarpey et al. recently undertook a “drain the pond” approach in which they systematically examined the …

Race and IQ: A Theory-Based Review of the Research in Richard Nisbett ’ s Intelligence and How to Get It

We provide a detailed review of data from psychology, genetics, and neuroscience in a point-counterpoint for- mat to enable readers to identify the merits and demerits of each side of the debate over whether the culture-only (0% ge- netic-100% environmental) or nature + nurture model (50% genetic-50% environmental) best explains mean ethnic group differences in intelligence test scores: Jewish (mean IQ = 113), East Asian (106), White (100), Hispanic (90), South Asian (87), African American (85), and sub-Saharan African (70). We juxtapose Richard Nisbett's position, expressed in his book Intelligence and How to Get It, with our own, to examine his thesis that cultural factors alone are sufficient to explain the differences and that the nature + nurture model we have presented over the last 40 years is unnecessary. We review the evidence in 14 topics of contention: (1) data to be explained; (2) malleability of IQ test scores; (3) culture- loaded versus g-loaded tests; (4) stereotype threat, caste, and X factors; (5) reaction-time measures; (6) within-race heri- tability; (7) between-race heritability; (8) sub-Saharan African IQ scores; (9) race differences in brain size; (10) sex dif- ferences in brain size; (11) trans-racial adoption studies; (12) racial admixture studies; (13) regression to the mean effects; and (14) human origins research and life-history traits. We conclude that the preponderance of evidence demonstrates that in intelligence, brain size, and other life history traits, East Asians average higher than do Europeans who average higher do South Asians, African Americans, or sub-Saharan Africans. The group differences are between 50 and 80% heritable.

Integrating frequency-based mathematics instruction with a multi-level assessment system to enhance response to intervention frameworks.

to Intervention (RtI) refers to a recent innovation education utilizing a multitiered service delivery model with two overlapping functions: first, to identify students who are struggling classroom and remediate academic deficits, and second, to distinguish between students who are behind due to a history of poor instructional experiences and those need of special education services for remediation of an actual learning disability. (Jenkins, Hudson, & Johnson, 2007). promotes a new focus on teaching and learning, focusing on how responsive students are to instruction. The term as originally coined, Responsiveness places agency or label of special education on teaching methodologies and measures student responsiveness to those procedures. was derived from provisions outlined Individuals with Disabilities Improvement Act of 2004 (IDEA, 2004), which states that in determining whether a child has a specific learning disability, a Local Education Agency may use a that determines if child responds to scientific, research-based intervention as part of evaluation process [Section 614 (b)(6)(B)]. As such, offers an alternative to traditional practice of diagnosing learning disabilities based on a pronounced dual discrepancy between intellectual capacity (as determined by intelligence tests) and academic proficiency various subjects (as determined by achievement tests). is not mandated, but IDEA 2004 now prohibits states from requiring this discrepancy model. In many ways, constitutes a profound paradigm shift way that students with educational problems are perceived and taught classroom. According to traditional approach, if a significant dual discrepancy is observed between intelligence test scores and achievement scores, problem is generally considered to exist within student. The student is then labeled with a learning disability and committed to special educational system. If a significant discrepancy is not observed, student returns to general education classroom. Due to strict qualification guidelines related to current provision of special education services, funding to provide additional support to students that are only marginally failing is not generally available. Yet, it's clear that without an effective intervention, deficits are only likely to increase. For this reason, dual discrepancy model is often referred to as wait-to-fail model and has come under increasing widespread criticisms as being an ineffective and inadequate for special education (Francis et al., 2005). In contrast to dual discrepancy approach, emphasizes identifying and supportng all students with pronounced academic deficits. This change perspective of how to provide services has even led to a new term, the enabled learner (Tilly, 2006) and is creating a challenge for our school psychologists to move from use of traditional psychometric tests (i.e. intelligence and achievement tests) to an edumetric problem solving model focused on measuring changes individual performance over time (Canter, 2006). In summary, RtI is a set of scientifically research-validated practices that are deployed schools using scientific method as a decision-making framework (Tilly, 2006 p. 22). Framework When a school-wide approach is adopted, most commonly utilizes what is referred to as Standard Protocol Model (Shores & Chester, 2009). The model was based on research curriculum-based measurement of reading skills conducted by Deno and Mirkin (Deno, 1985, 2003; Deno & Mirkin, 1977). CBM grew out of need for educators to access more frequent performance data academic foundation skills of reading, spelling, writing, and mathematics (Deno, 1985; Shinn 1989). Teachers can use these criterion-referenced assessments to compare student progress to a grade level standard as well as to analyze individual growth compared to previous performance. …

Emotional Intelligence as a Predictor for Clinical Performance in Professional Physical Therapy Students

Background and Purpose. The purpose of the admission process in the graduate physical therapy (PT) program is to evaluate information that can predict an individual’s potential for success in the program. To date there is no reliable way to predict clinical performance of physical therapy students. Emotional intelligence has been shown to predict clinical performance in other medical professions and may be a predictor for clinical performance in PT. Generic abilities of clinical performance are critically important in the PT profession and are evaluated using the Clinical Performance Instrument (CPI). This study examined the relationship between clinical performance and emotional intelligence. Subjects. Fifty-six graduate physical therapy students (46 female, 10 male) between the ages of 23 to 38 years (25.7 + 3.6 years) from four Eastern Massachusetts schools participated. Methods. Clinical Performance Instrument (CPI) scores (version 4), the Mayer-Salovey-Caruso Emotional Intelligence Test (MSCEIT version 2.0)scores, Graduate Record Exam (GRE) scores, pre-requisite grade point averages (GPAs) and demographic information were collected. Results. Total CPI score (R2 = 0.36, p <0.02) and scores on individual items of Professional behavior (R2 = 0.31), Performing Interventions (R2 = 0.35, p < 0.04) and Performing an Examination (R2 = 0.28) were not significantly related to emotional intelligence. Emotional intelligence was not significantly related to GRE scores (r =.14, p = 0.31) or pre-requisite school GPA (r = 0.10, p = 0.46). Discussion and Conclusion. Within the limitations of this research, the MSCEIT did not prove to be a successful predictor either by itself or in combination with other variables in predicting CPI performance. Future work with emotional intelligence surveys as predictors of CPI performance should start with examining those who pass the clinical experience part of the PT program compared to those who do not. After understanding the relationship between success and failure on the CPI, an examination of those that score high on the CPI versus those that merely pass could be studied.

Gender difference in speech intelligibility using speech intelligibility tests and acoustic analyses

PURPOSEThe purpose of this study was to compare men with women in terms of speech intelligibility, to investigate the validity of objective acoustic parameters related with speech intelligibility, and to try to set up the standard data for the future study in various field in prosthodontics.MATERIALS AND METHODSTwenty men and women were served as subjects in the present study. After recording of sample sounds, speech intelligibility tests by three speech pathologists and acoustic analyses were performed. Comparison of the speech intelligibility test scores and acoustic parameters such as fundamental frequency, fundamental frequency range, formant frequency, formant ranges, vowel working space area, and vowel dispersion were done between men and women. In addition, the correlations between the speech intelligibility values and acoustic variables were analyzed.RESULTSWomen showed significantly higher speech intelligibility scores than men and there were significant difference between men and women in most of acoustic parameters used in the present study. However, the correlations between the speech intelligibility scores and acoustic parameters were low.CONCLUSIONSpeech intelligibility test and acoustic parameters used in the present study were effective in differentiating male voice from female voice and their values might be used in the future studies related patients involved with maxillofacial prosthodontics. However, further studies are needed on the correlation between speech intelligibility tests and objective acoustic parameters.

Competence in Intelligence Testing: A Training Model for Postgraduate Psychology Students

AbstractThe assessment of intellectual ability is a core competency in psychology. The results of intelligence tests have many potential implications and are used frequently as the basis for decisions about educational placements, eligibility for various services, and admission to specific groups. Given the importance of intelligence test scores, accurate test administration and scoring are essential; yet there is evidence of unacceptably high rates of examiner error. This article discusses competency and postgraduate training in intelligence testing and presents a training model for postgraduate psychology students. The model aims to achieve high levels of competency in intelligence testing through a structured method of training, practice and feedback that incorporates peer support, self-reflection and multiple methods for evaluating competency.

The Flynn effect in sibships: Investigating the role of age differences between siblings

Abstract The aim of the study was to investigate the relationship between the Flynn effect and the effects of age differences between siblings on the intelligence difference between them. In Norway, the secular trends in intelligence-test score means vary both in magnitude and direction. We identified three periods: one period where the mean intelligence increased across birth cohorts (1950–1956), one period where the means decreased (1976–1983), and one period with no appreciable Flynn effect (1960–1965). In a data base comprising birth year and intelligence data on more than 900,000 males meeting at mandatory conscription between their 18th and 21st birthday, we identified more than 69,000 brother pairs where both brothers had been born in exactly one of the periods mentioned above. In this study group the relationship between age differences between brothers and the intelligence difference could be studied. The results showed that in the period with increasing intelligence means across cohorts, the intelligence difference between brothers decreased with increasing age differences. In the period with decreasing means, the difference between the later-born and the earlier-born brother increased across age differences. No systematic effects of age difference on mean intelligence differences were found in the period without a Flynn effect. Regression analyses showed that the Flynn effect can be quite well predicted from the effects of the age differences between brothers on their intelligence-test scores. We conclude that the factors causing the Flynn effect also work within sibships. Hypotheses positing that the Flynn effect is solely caused by between-families factors (e.g. the heterosis hypothesis) are weakened. The present results also entail that the birth order effect observed in Norway is in part conditional on the Flynn effect.

Normas do Teste de Inteligência Não Verbal R-1 para adultos não alfabetizados

O R-1: Teste de Inteligência Não Verbal é um teste de fator g brasileiro, que foi criado para ser utilizado na avaliação de motoristas, candidatos à Carteira Nacional de Habilitação (CNH). O manual mais recente deste teste não traz tabelas para uso com analfabetos. O objetivo deste estudo foi estabelecer normas do Teste R-1 para adultos não alfabetizados e apresentar uma análise das frequências de acertos para cada item. A amostra foi composta por 151 adultos de 16 a 77 anos, de ambos os sexos, frequentando cursos de alfabetização na cidade de São Paulo. O Teste R-1 foi aplicado coletivamente sem limite de tempo. Os resultados indicaram que as médias dos adultos analfabetos foram mais baixas do que as das pessoas com maior escolaridade, confirmando que a escolaridade exerce uma influência nas pontuações dos testes de inteligência, conforme é apontado pela literatura. A comparação da porcentagem de acertos de cada item nesta amostra com as de pessoas com maior escolaridade indicou que os itens apresentaram a mesma dificuldade relativa, com porcentagens de acerto mais baixas. Palavras-chave: Teste R-1; analfabetismo; desenvolvimento intelectual; testes de inteligência.

Register data suggest lower intelligence in men born the year after flu pandemic

To test the hypothesis that prenatal exposure to the Hong Kong flu, an influenza pandemic that haunted Europe during winter 1969 to 1970, was associated with reduced intelligence in adulthood. Data from the Medical Birth Register of Norway were linked with register data from the National Conscript Service. The sample comprised all registered boys born alive in single birth after 37 to 43 weeks' gestation during 1967 to 1973 (n = 205,634). Intelligence test scores, recorded at military conscription, were available for 182,913 individuals. The mean intelligence score increased from one birth year to another, except for a downturn in 1970. The birth year 1970 was inversely associated with intelligence score (-0.03 standard deviation [SD]; p < 0.001) after adjustments for birth characteristics, parental characteristics, and the trend of increasing scores over the 7 birth years. Analyses with the sample stratified by birth month showed that the inverse association between the birth year 1970 and intelligence score was significant only among men born in July (-0.04 SD; p = 0.049), August (-0.05 SD; p = 0.013), September (-0.09 SD; p < 0.001), and October (-0.06 SD; p = 0.008). Thus, the intelligence scores of the men born 6 to 9 months after the epidemic were lower than the mean values for the men born in the same months a few years before or after. Early prenatal exposure to the Hong Kong flu may have interfered with fetal cerebral development and caused reduced intelligence in adulthood.

Interpretation of Intelligence Test Scores in Atkins Cases: Conceptual and Psychometric Issues

So-called Atkins cases refer to individuals who have been sentenced to death for capital crimes who claim that the death penalty constitutes “cruel and unusual punishment” under the Eighth Amendment. Psychological testimony is influential because this testimony strikes at the very core issue in these cases; namely, whether or not the individual is mentally retarded. Despite the importance of psychological testimony, courts have not been made to understand the subtleties and complexities of the issues in diagnosing mental retardation. Five such issues are discussed in this article: (a) the nature of intellectual functioning, (b) the Flynn Effect, (c) measurement error, (d) practice effects, and (e) the nature of school “diagnoses.” Examples of each of these issues are illustrated with an actual Atkins case (Walker v. True, 2006).

Group differences in the heritability of items and test scores

It is important to understand potential sources of group differences in the heritability of intelligence test scores. On the basis of a basic item response model we argue that heritabilities which are based on dichotomous item scores normally do not generalize from one sample to the next. If groups differ in mean ability, the functioning of items at different ability levels may result in group differences in the heritability of items, even when these items function equivalently across groups and the heritability of the underlying ability is equal across groups. We illustrate this graphically, by computer simulation, and by focusing on several problems associated with a recent study by Rushton et al. who argued that the heritability estimates of items of Raven's Progressive Matrices test in North-American twin samples generalized to other population groups, and hence that the population group differences on this test of general mental ability (or intelligence) had a substantial genetic component. Our results show that item heritabilities are strongly dependent on the group on which the heritabilities were based. Rushton et al.'s results were artefactual and do not speak to the nature of population group differences in intelligence test performance.

Association of Apgar score at five minutes with long-term neurologic disability and cognitive function in a prevalence study of Danish conscripts.

BackgroundApgar score is used for rapid assessment of newborns. Low five-minute Apgar score has been associated with increased risk of severe neurologic outcome, but data on milder outcomes, particularly in the long term, are limited. We aimed to examine the association of five-minute Apgar score with prevalence of neurologic disability and with cognitive function in early adulthood.MethodsWe conducted a prevalence study among draft-liable men born in Denmark in 1978–1983 and presenting for the mandatory army evaluation in a northern Danish conscription district. We linked records of this evaluation, which includes medical exam and intelligence testing, with the conscripts' records in the Medical Birth Registry, containing perinatal data. We examined prevalence of neurologic disability and of low cognitive function according to five-minute Apgar score.ResultsLess than 1% (136/19,559) of the conscripts had 5-minute Apgar scores <7. Prevalence of neurologic disability was 2.2% (435/19,559) overall; among conscripts with Apgar scores <7, 7–9, and 10 (reference), it was 8.8%, 2.5%, and 2.2% respectively. The corresponding prevalences of low cognitive function (intelligence test score in the bottom quartile) were 34.9%, 27.2%, and 25.0%. The outcomes were more prevalent if Apgar score <7 was accompanied by certain fetal or obstetric adversities. After accounting for perinatal characteristics, 5-mintue Apgar score <7 was associated with prevalence ratios of 4.02 (95% confidence interval: 2.24; 7.24) for neurologic disability and 1.33 (0.94; 1.88) for low cognitive function.ConclusionA five-minute Apgar score <7 has a consistent association with prevalence of neurologic disability and with low cognitive function in early adulthood.

Learning During Dynamic Testing: Variability in Strategy Use by Indigenous and Ethnic Minority Children

The objective of this study was to explore whether dynamic testing of indigenous and ethnic minority children could provide information concerning changes in their strategy use during testing. It was hypothesized that dynamic testing with graduated prompting and trial-by-trial-assessment could reveal the development of children’s strategy use while tested. The participants were indigenous Dutch and ethnic minority children. Trial-by-trial-testing provided information of how strategy use developed during training. Experimental-group children showed significant changes towards more advanced strategies. Ethnic minority children showed most strategy changes during training, initially needing more prompting but progressively requiring less. The study provided insight into strategy use during and after training. Pretest strategy level was found to be the first predictor of posttest strategy level, followed by condition and ethnicity. Age, gender, and intelligence test scores did not change this order. The relatively short dynamic intervention provides insights into children’s strategy use and their response to prompting, particularly for ethnic minority children.

Childhood IQ and in-service mortality in Scottish Army personnel during World War II

The Scottish Mental Survey of 1932 (SMS1932) provides a record of intelligence test scores for almost a complete year-of-birth group of children born in 1921. By linking UK Army personnel records, the Scottish National War Memorial data, and the SMS1932 dataset it was possible to examine the effect of childhood intelligence scores on wartime military service mortality in males. There were 491 matches between World War II (WWII) Scottish Army fatalities and the SMS1932 database; 470 (96%) had an age 11 mental ability score recorded. The mean (S.D.) age 11 IQ score of those who died on active service in WWII was 100.78 (15.56), compared with 97.42 (14.87) for male Army survivors ( p < 0.0001; Cohen's d = 0.22). Men who took part in the SMS1932 and who were not found in the Army database had a higher mean score (100.45, S.D. =14.97) than those men who had been in the Army, regardless of whether they died or survived (mean IQ = 97.66, S.D. = 14.94; p < 0.0001; Cohen's d = 0.19). Male soldiers with a higher childhood IQ had a slightly increased risk of dying during active service in WWII. Men who did not join the Army had a higher IQ than men who did. Further research in this area should consider naval and air force personnel records in order to examine more fully the complex relationship between IQ and survival expectancy during active service in WWII.

Personality, Intelligence and Assessment Centre Expert Ratings

Just under 3000 middle managers were rated on seven dimensions/competencies by consultants after a 1-day assessment centre and structured interview. They also completed two cognitive ability tests and two well-established personality tests (NEO PI-R; MBTI). Correlational analysis showed that the rated dimensions of ‘drive to achieve’, ‘internal locus of control’ and ‘resilience’ all modestly negatively correlated with Neuroticism. All seven ratings were significantly correlated with Extraversion and three each with Openness and Agreeableness. There were few significant correlations with the MBTI but the Thinking–Feeling dimension correlated significantly with combined ratings. Correlations with the intelligence test scores were mostly non-significant. The seven ratings factored into three identifiable factors: labelled personal assertiveness, toughness and determination and curiosity. Regressions using both a total, overall computed rating of general aptitude, as well as the three scores as criterion variables and ability, personality, participant-gender and management level as predictor variables demonstrated that they accounted for between a quarter and a third of the variance. Predictors varied considerably as a function of the different criteria measures but ability and gender accounted for little of the variance.

Exploring possible neural mechanisms of intelligence differences using processing speed and working memory tasks: An fMRI study

To explore the possible neural foundations of individual differences in intelligence test scores, we examined the associations between Raven's Matrices scores and two tasks that were administered in a functional magnetic resonance imaging (fMRI) setting. The two tasks were an n-back working memory ( N = 37) task and inspection time ( N = 47). The subjects were members of the Aberdeen Birth Cohort 1936, aged in their mid–late 60s when tested for this study. Performance on both tasks was correlated significantly with scores on Raven's Matrices. In the inspection time task there were regions with significant correlations between the neural activity (BOLD response) and performance but not between BOLD response and scores on Raven's Matrices. In the working memory task there were no significant correlations between BOLD response and either performance or scores on Raven's Matrices. Moreover, there was almost no mediation of the Raven's Matrices versus n-back and inspection time scores correlations by the respective BOLD response. These findings partially replicate important aspects of a prominent report in this field [Gray, J.R., Chabris, C.F., & Braver, T.S. (2003). Neural mechanisms of general fluid intelligence. Nature Neuroscience, 6, 316–322.], but have also extended the those finding into both a unique population and a novel functional task.

An exploratory analysis of the use of cognitive, adaptive and behavioural indices for cluster analysis of ASD subgroups

Autism spectrum disorder (ASD) includes symptoms that vary in severity and frequency between children. Consequently, multiple psychometric assessment procedures are recommended to detect an ASD, including scales which asses the presence and nature of ASD-related behaviour. However, to date, few studies have examined the relative and specific contribution which such behaviourally oriented scales can make to the diagnosis of individual children with ASD. Cluster analysis was used to explore the common characteristics of a group of 53 preschool and elementary school children with an ASD, based upon scores on tests of cognitive ability, adaptive behaviour and behavioural checklists designed to measure the presence of typical ASD. Data confirmed the expected variability in intelligence test scores. In addition, measures of adaptive behaviour and data from a behaviourally based rating scale suggested that children with Asperger's Disorder and autism might be reclassified into subgroups according to the presence of particular ASD-specific behaviours. As well as confirming that children with ASD vary in their adaptive behaviour and cognitive levels, these data emphasise the limited contribution such assessment procedures make to an understanding of the child's day-to-day behaviour and functioning, thus arguing for the inclusion of behaviourally based rating scales to develop ideographic intervention plans.

Intelligence Correlations Between Brothers Decrease With Increasing Age Difference

Research on twins and unrelated persons living together indicates that, although differences in intelligence between persons are caused by both genetic and environmental factors, similarities--and especially those between adults--are mostly or exclusively due to shared genes. However, twin and adoption designs have been criticized for incorrectly estimating the effects of the environment on the similarity between relatives, and studies of environmental effects in other family constellations may be enlightening. In a sample comprising more than 334,000 pairs of brothers (ages 18-21 years) who were tested at the mandatory conscription for military service in Norway, correlations between brothers' intelligence-test scores decreased with increasing age difference between the brothers. This result indicates that family environmental factors have an impact on the intelligence of young adults. Analyses of subgroups defined by family size and parental education demonstrated that the effects of age difference are essentially independent of these factors.