Intelligence: new findings and theoretical developments

We review new findings and new theoretical developments in the field of intelligence. New findings include the following: (a) Heritability of IQ varies significantly by social class. (b) Almost no genetic polymorphisms have been discovered that are consistently associated with variation in IQ in the normal range. (c) Much has been learned about the biological underpinnings of intelligence. (d) "Crystallized" and "fluid" IQ are quite different aspects of intelligence at both the behavioral and biological levels. (e) The importance of the environment for IQ is established by the 12-point to 18-point increase in IQ when children are adopted from working-class to middle-class homes. (f) Even when improvements in IQ produced by the most effective early childhood interventions fail to persist, there can be very marked effects on academic achievement and life outcomes. (g) In most developed countries studied, gains on IQ tests have continued, and they are beginning in the developing world. (h) Sex differences in aspects of intelligence are due partly to identifiable biological factors and partly to socialization factors. (i) The IQ gap between Blacks and Whites has been reduced by 0.33 SD in recent years. We report theorizing concerning (a) the relationship between working memory and intelligence, (b) the apparent contradiction between strong heritability effects on IQ and strong secular effects on IQ, (c) whether a general intelligence factor could arise from initially largely independent cognitive skills, (d) the relation between self-regulation and cognitive skills, and (e) the effects of stress on intelligence.     

弱智儿童视觉图形辨认的实验研究

本研究探讨了不同智商水平的弱智儿童的视觉图形辨认能力的差异,并与同龄正常儿童作了比较。结果表明,智商在31-51,平均智商为41.6,均龄为11.7岁的弱智儿童,在图形以0.05秒速度的呈现条件下,平均辨认正确率为21.4%;在以0.01秒速度呈现的条件下,平均正确率为20.7%。智商在55-75,平均智商为62.0,均龄为10.2岁的弱智儿童,图形以0.05秒速度呈现时,平均辨认正确率为48.5%;在以0.01秒速度呈现时,平均正确率为45.0%。与同均龄的正常儿童比较,无论在哪一种呈现速度条件下,对图形辨认正确率均明显低于正常儿童。     

The modification of intelligence through early experience

Infants judged to be at risk for subnormal intellectual growth were randomly assigned to an Experimental (N = 27) or a Control (N = 25) group. Infants in both groups received medical care and dietary supplements; their families received social work services on a request basis. Experimental children participated in an educational daycare program beginning before the third month of life. The daycare program was composed, in part, of curriculum activities designed to stimulate intellectual growth. Between 6 and 36 months of age, Experimental children maintained normal intellectual growth; Control children declined in IQ beginning between 12 and 18 months of age and remained significantly lower than Experimental children at 24 and 36 months. The mother-child IQ correlation for Control dyads was 43; for Experimental dyads the correlation was ?.05. These two types of evidence are interpreted as support for the importance of early environments in the development of intelligence.     

Intelligence and Creativity: Over the Threshold Together?

Threshold theory predicts a positive correlation between IQ and creativity scores up to an IQ level of 120 and no correlation above this threshold. Primary school children were tested at beginning (N = 98) and ending (N = 70) of the school year. Participants performed the standard progressive matrices (SPM) and the Test of Creative Thinking—Drawing Production (TCT-DP). Each child with IQ ≥ 120 was grade-and-gender matched to a child with IQ < 120. Results in accordance with the threshold theory were found only for female children in the highest grade level (Grade 4). Longitudinal analysis implies that a subgroup of children goes down in IQ and creativity simultaneously, possibly due to motivational issues. Their correlated scores may be a source of evidence for the threshold theory. The relationship between intelligence and creativity is not straightforward and depends on a combination of factors including grade level and gender.     

Investigating the neurodevelopmental mediators of aggression in children with a history of child maltreatment:An exploratory field study

Maltreatment of children is a chronic community problem that increases the risk of future aggression. Despite several decades of research highlighting this relationship, few studies have explored the potential neuropsychological deficits that are likely to mediate it. This exploratory study aimed to examine how child maltreatment may be associated with aggression via impairment in the developing prefrontal-limbic-autonomic pathways that are implicated in neuropsychological models of aggression. Furthermore, it aimed to investigate the relationship between child maltreatment and both reactive and proactive aggression subtypes. To investigate this non-invasively in an at-risk population, children with a documented protective care history (n = 20) and a community control group (n = 30), aged between 6 and 12 years, were compared on measures of cardiovascular functioning, affect regulation and cognitive functioning aligned with this neuropsychological model. Whilst no group differences were found on cardiovascular functioning (i.e., resting heart rate, heart rate reactivity, heart rate variability), the protective care group performed significantly worse on measures of affect regulation and cognitive functioning (i.e., global intelligence, executive functioning, smell identification and social cognition). The relationship between child maltreatment and aggression was mediated by executive dysfunction and affect dysregulation but not global IQ, social cognition or olfactory identification. The results suggest that interventions targeting aggression in maltreated children will benefit from clinical assessment and psychological strategies that address the executive dysfunction and affect dysregulation that has been associated with this clinical outcome.     

Recognition memory and intelligence

The assumption that individual differences in recognition memory are associated with individual differences in intelligence was explored by administering intelligence tests and tests of immediate visual recognition memory to a sample of 52 5-year-old children expected to vary widely from one another in intelligence. Each child was given the Peabody Picture Vocabulary Test (Form L) and two tests of immediate recognition memory: one test for 27 abstract patterns and one test for 27 unfamiliar cartoon faces. The mean PPVT-IQ for the sample was in the average range at 98.1. Interindividual variability in IQ proved to be high as reflected in the group SD of 22.6, with scores ranging from 40 to 136. The recognition tasks proved to be of moderate difficulty. Individual differences in memory for patterns were highly related to memory for faces (r = .76), indicating that the overall recognition test was reliable. The most important result of the present study was the strong association between recognition memory performance and PPVT-IQ of .70. The relation between recognition memory and IQ could not be accounted for by the inclusion of a few very low IQ children, since the association remained high at .61 when children with IQs below 75 were omitted from analysis. In short, the present results indicate that immediate recognition memory is highly associated with intelligence.     

Environment and high IQ—A consideration of fluid and crystallized intelligence

Attention is drawn to some causes of distancing between fluid and crystallized intelligence through detailed testing, environmental observations and responses of 210 children, their families and teachers. High Gc children (with IQ scores of 141+) were associated with educationally-superior home backgrounds, but not with abnormal emotional or personality features. High Gf children (99th% Raven's scorers) were found to reflect specifically the Cultural Milieu and Achievement-Related Facilities of their homes in their high IQ scores, but where Gf was insufficiently provided with opportunity, Gc appeared to suffer.Calculated proportions of fluid and crystallized intelligence in high IQ were varied, the scores becoming more heavily loaded with environmental influences towards the top of the scale, being 26% for children of exceptionally-high Gf and 13% for those of average to high Gf. It is suggested that where an IQ test is used, a cut-off point of IQ 130 be taken for the identification of intellectually-gifted children, along with verbal and other specific-ability tests.     

Physiological correlates of intellectual function in children with sickle cell disease: hypoxaemia, hyperaemia and brain infarction

Lowered intelligence relative to controls is evident by mid-childhood in children with sickle cell disease. There is consensus that brain infarct contributes to this deficit, but the subtle lowering of IQ in children with normal MRI scans might be accounted for by chronic systemic complications leading to insufficient oxygen delivery to the brain. We investigated the relationship between daytime oxyhaemoglobin saturation (SpO2), cerebral blood flow velocity (CBFV) and intellectual function (IQ) using path-analysis in 30 adolescents with sickle cell disease (mean age 17.4 years, SD 4.2). Initial analyses revealed that the association between SpO2 and Full Scale IQ (FSIQ) was fully mediated by increased CBFV, whereby SpO2 was negatively correlated with CBFV and CBFV was negatively correlated with FSIQ, i.e. decreases in oxygen saturation are associated with increases in velocity, and increased velocity is associated with lowered IQ scores. The mediated relationship suggests that lowered IQ may be a function of abnormal oxygen delivery to the brain. Further analyses showed that the association between CBFV and IQ was significant for verbal but not for performance IQ. The pathophysiology characteristic of SCD can interfere with brain function and constrain intellectual development, even in the absence of an infarct. This supports the hypothesis that lowered intellectual function is partly explained by chronic hypoxia, and has wider implications for our understanding of SCD pathophysiology.     

Intelligence and regional brain volumes in normal controls

The relationship between brain size and intelligence was examined in a large sample of healthy normal volunteers (N = 90). In addition to confirmation of the small but significant relationship between IQ and whole brain volume (r = 0.25, p < .05) using magnetic resonance imaging, regional differences were examined using a completely automated procedure to generate lobar volumes to address questions related to regional specificity and its relationship to intelligence. A significant positive relationship was found between measures of full scale IQ and frontal (r = 0.25, p < .05) and temporal (r = 0.28, p < .01) regions, although when correlations across different brain regions were tested against each other, there was no evidence of regional specificity. In addition, no laterality effects were seen. Correlations between WAIS-R subtest scores and brain regions indicated few correlations between verbal subtest scores and brain size, but several significant correlations between the performance subtest scores and frontal, temporal, parietal, and cerebellar brain regions. These results support the notion of a modest relationship between brain size and measures of global intelligence and suggest diffuse brain involvement on performance tasks which require integration and use of multiple cognitive domains.     

Sensory Discrimination,Working Memory and Intelligence in 9‐Year‐Old and 11‐Year‐Old Children

More than a century ago, Galton and Spearman suggested that there was a functional relationship between sensory discrimination ability and intelligence. Studies have since been able to confirm a close relationship between general discrimination ability (GDA) and IQ. The aim of the present study was to assess whether this strong relationship between GDA and IQ could be due to working memory (WM) demands of GDA tasks. A sample of 140 children (seventy 9‐year‐olds and seventy 11‐year‐olds) was studied. Results showed that there was a significant overlap between WM, GDA and fluid intelligence. Furthermore, results also revealed that WM could not explain the relationship between GDA and fluid intelligence as such, but that it acted as a bottleneck of information processing, limiting the influence of GDA on the prediction of fluid intelligence. Specifically, GDA's influence on the prediction of intelligence was only visible when WM capacity was above a certain level. Copyright © 2013 John Wiley & Sons, Ltd.     

Attentional WM is not necessarily specifically related with fluid intelligence: the case of smart children with ADHD symptoms

Executive functions and, in particular, Attentional (active) Working Memory (WM) have been associated with fluid intelligence. The association contrasts with the hypothesis that children with ADHD exhibit problems with WM tasks requiring controlled attention and may have a good fluid intelligence. This paper examines whether children who are intelligent but present ADHD symptoms fail in attentional WM tasks. The latter result would be problematic for theories assuming the generality of a strict relationship between intelligence and WM. To study these issues, a battery of tests was administered to a group of 58 children who all displayed symptoms of ADHD. All children were between the age of 8 and 11 years, and were described by their teachers as smart. Children were compared to a control group matched for age, schooling, and gender. The battery included a test of fluid intelligence (Raven’s Coloured Matrices), and a series of visuospatial WM tasks. Results showed that children with ADHD were high in intelligence but significantly lower than the controls in WM tasks requiring high attentional control, whereas there was no difference in WM tasks requiring low attentional control. Furthermore, only high attentional control WM tasks were significantly related to Raven’s performance in the control group, whereas all WM tasks were similarly related in the ADHD group. It is concluded that performance in high attentional control WM tasks may be related to fluid intelligence, but also to a specific control component that is independent of intelligence and is poor in children with ADHD.     

Assessment of the global intelligence and selective cognitive capacities in preterm 8-year-old children

The aim of this study was to assess various cognitive abilities such as attention, IQ, reasoning, and memory related to academic achievement in 8- and 9-year-old preterm children. A total of 141 children were assessed. The preterm group (=37 weeks) comprised 63 children and was compared to 78 full-term children. Attention was evaluated using the d2 Selective Attention test, and the IQ by the L-M form of the Stanford-Binet Intelligence Scale, establishing a profile of abilities: perception, memory, comprehension, reasoning, and verbal fluency. Significant differences in IQ were found between the preterm and full-term children. Of the cognitive abilities assessed, the only significant differences were found in verbal fluency, with preterm boys showing lower verbal fluency scores than full-term children. In conclusion, all preterm groups have attention ability similar to that of full-term children. However, preterm children obtain lower scores in intelligence measures. In addition, preterm boys have verbal fluency difficulties. Taking into account the increase in preterm births, suitable intervention programs must be planned to attend the difficulties found.     

Dietary patterns and intelligence in early and middle childhood

The association between intelligence and diet at 3.5 and 7 years was examined in 591 children of European descent. Approximately half of the children were born small-for-gestational age (birth weight ≤ 10th percentile). The relationship between IQ and diet (measured by food frequency) was investigated using multiple regression analyses. Eating margarine at least daily was associated with significantly lower IQ scores at 3.5 years in the total sample and at 7 years in SGA children. For all children, eating the recommended daily number of breads and cereals was associated with significantly higher IQ scores at 3.5 years, and those who ate fish at least weekly had significantly higher IQ scores at 7 years than those who did not. The consumption of fish, breads and cereals commeasurable with nutritional guidelines may be beneficial to children's cognitive development. In contrast, consuming margarine daily was associated with poorer cognitive functioning. Further research is needed to identify the nutrients that may underlie this association.     

What Does the DAP:IQ Measure?: Drawing Comparisons between Drawing Performance and Developmental Assessments

Human figure drawing tasks such as the Draw-a-Person test have long been used to assess intelligence (F. Goodenough, 1926). The authors investigate the skills tapped by drawing and the risk factors associated with poor drawing. Self-portraits of 345 preschool children were scored by raters trained in using the Draw-a-Person Intellectual Ability test (DAP:IQ) rubric (C. R. Reynolds & J. A. Hickman, 2004). Analyses of children's fine motor, gross motor, social, cognitive, and language skills revealed that only fine motor skill was an independent predictor of DAP:IQ scores. Being a boy and having a low birth weight were associated with lower DAP:IQ scores. These findings suggest that although the DAP:IQ may not be a valid measure of cognitive ability, it may be a useful screening tool for fine motor disturbances in at-risk children, such as boys who were born at low birth weights. Furthermore, researchers who use human figure drawing tasks to measure intelligence should measure fine motor skill in addition to intelligence.     

Diagnostic implications of McCarthy scale general cognitive index/binet IQ discrepancies for low-socioeconomic-status preschool children

This study compared McCarthy Scale General Cognitive Index (GCI) and Stanford-Binet IQ discrepancies for both normal and handicapped preschool children of low socioeconomic status (SES). Both tests were administered in counter-balanced order to a total of 70 children. The results of these comparisons yielded a significant positive relationship between GCI and IQ, as well as a significant discrepancy between the two scores, favoring IQ, of a relatively small magnitude (3.9 points). There were significant discrepancies favoring IQ for the subgroups of learning-disabled, speech-impaired, and mentally retarded, those for all but mentally retarded being of relatively small magnitude; thus, the learning-disabled group was not uniquely characterized by a large discrepancy. In contrast to results consistently favoring IQ over GCI, when age groups were compared, the younger, 3 year olds, showed the reverse, though nonsignificant, trend.     

The California short-form test of mental maturity 1963 edition as a screening device for educable mentally retarded programs

The effectiveness of the CTMM-SF 1963 Edition as a screening device for EMR classes was tested by obtaining means and correlations between the CTMM-SF and individual examinations for children who scored below IQ 80 on the CTMM-SF. The CTMM-SF was found to be essentially uncorrelated with individual intelligence test results and to underestimate systematically the intelligence of a substantial number of children. Its use as a screening device or as a measure of intelligence is questioned.     

II. The comparability of the WISC-R and WAIS among 16-year-old EMR children

Thirty 16-year-old EMR children were administered the WAIS and WISC-R in counterbalance order to determine the comparability of the two assessment instruments. The WAIS was found to yield significantly higher Verbal, Performance, and Full Scale IQ scores. The comparisons of corresponding subtests indicate that all WAIS subtests were significantly higher than the WISC-R except Picture Completion. Correlations between corresponding WAIS and WISC-R IQ scales and subtests, however, were significant. The results suggest differences between the two instruments among children of subnormal intelligence, thus presenting the possibility that a child may be differentially classified based on the selection of the intelligence test.     

Word identification in adults with mild mental retardation: does IQ influence reading achievement?

OBJECTIVE: To assess the relationship between word identification and intelligence in adults with mild mental retardation (IQ < 80). METHOD: A standardized evaluation was administered to 67 adults with mild mental retardation. The evaluation included a psychiatric interview, the WAIS-R, and a 2-h interview with a speech therapist and reading tests. RESULTS: Causes of mental retardation were diverse in the sample, and IQ scores ranged from 43 to 79 (mean score = 64). All subjects exhibited reading impairment, including 69% with severe impairment. No subject with an IQ score under 65 was able to perform adequately in the word identification tasks. Word identification was correlated with total and verbal IQ, but not with performance IQ. CONCLUSION: Our results suggest that, in contrast to subjects with normal intelligence, IQ score is correlated with reading in subjects with mild mental retardation. Finally, remediation should be preferentially implemented for subjects with IQ score greater than 65.     

The determinants of parents' beliefs about the intelligence their children: A study from Hong Kong

One hundred and ninety‐three Hong Kong parents (mean age 42.2 years) were given a structured interview / questionnaire concerning their own and their children's self‐estimated overall and multiple intelligence. Previous research suggested that males tend to give higher overall “g” estimates to their children and themselves than do females, as well as higher scores on mathematical and spatial intelligence (Furnham, 2001). Further, studies in the West suggest that parents think their children are significantly brighter than they are and that their sons are brighter than their daughters. Estimates were lower than those found in Western populations but, even so, males rated their own mathematical and spatial intelligence higher than did females. Hong Kong Chinese parents did not think their sons were brighter than their daughters. The seven multiple intelligences factored into three clear factors for self and children, and regressions indicated that it was “academic” intelligence (verbal, mathematical, spatial) that was most “g” loaded. The child's age and the self‐rated overall IQ of both the parents were the best predictors of the child's overall estimated IQ. Less than a third of the parents had taken an IQ test or believed they measured IQ very well. Those who were more likely to be better educated, had taken an IQ test, and believed intelligence was inherited were more likely to award themselves higher overall IQ scores. Results are compared with the British studies in the same area.     

Prenatal maternal predictors of cognitive and emotional delays in children of adolescent mothers

The present study examined relationships among prenatal characteristics of 121 adolescent mothers-including cognitive readiness for parenting, intelligence, social support, and personal adjustment-and intellectual-linguistic development, social-emotional functioning, and adaptive behavior in their children at three years of age. Only 28% of the children scored within normal ranges on all three types of outcomes. Intellectual and linguistic delays were predicted best by prenatal measures of maternal Performance IQ and social support from extended family. Socioemotional problems were predicted best by maternal internalizing problems and social support from partner and friends. Adaptive behavior was associated with parenting style. Implications for the early identification of high-risk children--and associated intervention programs--are discussed.