Twin resemblances in cognitive abilities in an Egyptian sample

Thirty-six pairs of monozygotic (MZ) twins, 24 pairs of same-sexed dizygotic (DZ) twins, and 33 pairs of opposite-sexed DZ twins 12 to 19 years of age were tested in Minia, Egypt, on a battery of cognitive abilities tests. For most of the tests and composite scales, DZ resemblances were higher than typically found in Western samples and not significantly different from MZ resemblances. MZ resemblances were generally lower than typically found in Western samples. These results were discussed in terms of the influence of cross-cultural differences in degree of social stratification and assortative mating.This research was conducted while Anwar Abdel-Rahim was fully supported in the United States by grants from the Egyptian Government Ministry of Education and from Minia University. Dr. Abdel-Rahim wishes to thank Steven Vandenberg and his wife for their help and hospitality during his stay at the Institute for Behavioral Genetics in Boulder and to thank Drs. A. Kuse and K. W. Kang for their statistical advice. This paper was written while Craig Nagoshi was supported by NICHD Training Grant HD-07289.     

An analysis of Koch's (1966) Primary Mental Abilities Test data for 5- to 7-year-old twins

The purpose of this note is to present twin correlations based on analyses of Koch's (1966) Primary Mental Abilities Test data on 83 pairs of 5- to 7-year-old twins. The results yielded significant heritability for the Spatial subtest and suggested genetic influence on the Verbal and Quantitative subtests as well. An analysis of the phenotypic correlation between the Verbal and Spatial subtests suggested that verbal and spatial abilities are genetically independent at this age and that the relationship between the two abilities is mediated primarily by within-family environmental factors.This work was supported in part by NICHD Research Grant HD-10333 and NSF Research Grant BNS-7826204.     

Parent-offspring resemblance for specific cognitive abilities in Korea

Regressions of offspring on midparent value for tests of specific cognitive abilities in Korea were considerably higher than those for Americans of Japanese ancestry or Americans of European ancestry tested in Hawaii. This greater parent-offspring resemblance in Korea may be due to the particular method of test administration or to an increased genetic variance resulting from assortative mating. The pattern of parent-child correlations for three relatively pure tests of spatial ability and for the spatial factor did not conform to that of a sex-linked recessive character.The results reported here are made possible by collaboration of a group of investigators (G. C. Ashton, R. C. Johnson, M. P. Mi, and M. N. Rashad at the University of Hawaii, and J. C. DeFries, G. E. McClearn, S. G. Vandenberg, and J. R. Wilson at the University of Colorado) supported by NSF Grant GB-34720 and Grant HD-06669 from the National Institute of Child Health and Human Development.     

Genetic Structure of Spatial and Verbal Working Memory

Working memory (WM) encompasses both short-term memory (storage) and executive functions that play an essential role in all forms of cognition. In this study, the genetic structure of storage and executive functions engaged in both a spatial and verbal WM span task is investigated using a twin sample. The sample consists of 143 monozygotic (MZ) and 93 dizygotic (DZ) Japanese twin pairs, ages 16 to 29 years. In 155 (87 MZ, 62 DZ) of these pairs, cognitive ability scores from the Kyodai Japanese IQ test are also obtained. The phenotypic relationship between WM and cognitive ability is confirmed (r = 0.26–0.44). Individual differences in WM storage and executive functions are found to be significantly influenced by genes, with heritability estimates all moderately high (43%–49%), and estimates for cognitive ability comparable to previous studies (65%). A large part of the genetic variance in storage and executive functions in both spatial and verbal modalities is due to a common genetic factor that accounts for 11% to 43% of the variance. In the reduced sample, this common genetic factor accounts for 64% and 26% of the variance in spatial and verbal cognitive ability, respectively. Additional genetic variance in WM (7%–30%) is due to modality specific factors (spatial and verbal) and a storage specific factor that may be particularly important for the verbal modality. None of the variance in cognitive ability is accounted for by the modality and storage genetic factors, suggesting these may be specific to WM.     

Variability and stability in cognitive abilities are largely genetic later in life

The powerful quantitative genetic design of identical and fraternal twins reared apart (112 pairs) and matched twins reared together (111 pairs) was employed to assess the extent of genetic influence on individual differences in cognitive abilities during the last half of the life span. General cognitive ability yielded a heritability estimate of about .80 in two assessments 3 years apart as part of the Swedish Adoption/Twin Study of Aging. This is one of the highest heritabilities reported for a behavioral trait. Across the two ages, average heritabilities are about .60 for verbal tests, .50 for spatial and speed-of-processing tests, and .40 for memory tests. For general cognitive ability, the phenotypic stability across the 3 years is .92 and stable genetic factors account for nearly 90% this stability. These findings suggest that general cognitive ability is a reasonable target for research that aims to identify specific genes for complex traits.     

Multivariate path analysis of specific cognitive abilities in the colorado adoption project

A multivariate path model of genetic and environmental transmission was fitted to specific cognitive abilities data (verbal, spatial, perceptual speed, and visual memory) and evaluated using a maximum-likelihood estimation procedure. In this first multivariate behavioral genetic analysis of adoption data, cultural transmission was modeled via parental phenotypes, each parental phenotype being allowed to affect all traits in the offspring, and assortative mating and cross-assortative mating were accommodated. Results of a preliminary analysis indicated that selective placement is absent in this study. When the full model was fitted to the data, it was found that assortative mating is more important than cross-assortative mating but is substantial only for verbal ability. Genetic transmission parameters are modest in size, whereas cultural transmission is both small and nonsignificant. A simplified model in which cultural transmission and genotype-environment correlation are constrained to be zero provided a good fit to the data. Analyses of the structures of genetic and environmental correlation matrices indicated a strong genetic general factor and a similar, but weaker, environmental factor. Inspection of the genetic transmission parameters suggests that genetic continuity between early childhood and adulthood may be substantial for verbal ability, spatial ability, and perceptual speed.This work was supported in part by grants from the NSF (BNS-7826204 and BNS-8200310) and from the NICHD (HD-10333).     

A model of developmental change in hierarchical phenotypes with application to specific cognitive abilities

A hierarchical longitudinal path model is described for analysis of twin and sibling data. The model combines multivariate and longitudinal methodologies for assessment of continuity and change in the relationships among characters over time. Additionally, the model permits assessment of shared and independent etiologies for groups of measures at single and multiple occasions. The procedure is illustrated by application to specific cognitive ability data from 103 adopted and 109 nonadopted sibling pairs at ages 3, 4, 7, and 9 years, and 50 pairs of monozygotic and dizygotic twins at ages 3 and 4 years. The results suggest that much of the observed continuity in general intelligence measures is attributable to genetic influences common to specific abilities and indicate differential etiologies for specific abilities at different occasions in childhood.     

Multivariate path analysis of cognitive ability measures in reading-disabled and control nuclear families and twins

Matrix notation is used to formulate a multivariate path model of familial resemblance in nuclear families, monozygotic (MZ) twin pairs, and dizygotic (DZ) twin pairs. The model incorporates multivariate genetic and environmental influences, cultural transmission, assortative mating, and environmental influences shared by offspring, and it permits the estimation of genetic and environmental correlations. The model is applied to data from nuclear families, MZ twin pairs, and DZ twin pairs in which at least one child was diagnosed as being reading disabled and to data from control families and twins. Three cognitive ability measures (Reading, Coding Speed, and Spatial Ability) were analyzed simultaneously. Results indicate that genetic influences are moderate, with significant genetic correlations among characters. Cultural transmission is negligible, as are the environmental correlations. Assortative mating is significant only for the Reading measure. There is no evidence for sibling shared environmental influences; however, there are significant twin shared environmental effects for each measure but not between measures.This work was supported by grants from the Spencer Foundation and the NICHD (HD-11681) to J. C. DeFries and by NIMH Postdoctoral Training Grant MH-17104.     

Early assessment of sensorimotor and cognitive development in high-risk infants

Assessed 88 infants at risk for mental retardation on the Bayley Scales of Infant Development and a measure of visual recognition memory at 3 months corrected age. Bayley scales were administered again when the infants were 1-year-old. At 3 months of age the Bayley scales and the measure of visual recognition memory were not significantly correlated. Both measures, however, showed significant correlation to the Bayley scales administered at 1 year of age. Results from regression analyses indicated that each measure at 3 months of age was related to a different source of variance in the 1-year measure. These results are consistent with the hypothesis that at 3 months of age the visual recognition memory measure is a better early window into later cognitive development than the Bayley scales.     

Spouse similarity in newlyweds with respect to specific cognitive abilities,socioeconomic status,and education

Newlywed spouses (N=215 couples) were tested on 21 tests of specific cognitive abilities and responded to a questionnaire on their educational and socioeconomic (SES) background. A comparison of the present spouse correlations with those of long-standing marriages suggests that spouses resemble each other in abilities from the start and that the degree of resemblance changes little over time. The low spouse correlations for SES of origin (their parents) suggests that education is the chief SES variable by which spouse selection takes place. Spouse resemblance in education and parental SES could explain almost all of the spouse correlations in perceptual speed and spatial ability. However, a small but significant degree of spouse similarity in verbal and reasoning abilities was independent of education and SES.This article is an extension of a paper presented at the Eighth Annual Meeting of the Behavior Genetics Association in Davis, California, and is based on the first author's doctoral dissertation at the University of California, Berkeley, 1979. The research was supported in part by NIH Grant MH-23642 and NSF Grant BNS-77-00900K.     

Spectral EEG characteristics during increases in the complexity of the context of cognitive activity

The spatial and frequency characteristics of cortical electrical activity were studied in healthy human subjects in two series of experiments involving solution of sequentially presented visual tasks. The first task was to assess the relative sizes of two circles and was identical in both series. In the first series, this was supplemented by a task consisting of recognition of pseudowords/words, presumptively also requiring predominant involvement of the ventral “what?” visual system. In the second series, the additional task (spatial localization of a target stimulus in a matrix of letters) was associated with the predominant involvement of the dorsal “where?” visual system. Cortical electrical activity immediately before presentation of pairs of tasks was analyzed. Measures of EEG spectral power in the frontal, central, occipital, and temporal areas of the cortex was subjected to dispersion analysis. The power of electrical potentials in the delta and beta1 frequency ranges was greater when both tasks were associated predominantly with activation of the ventral visual system (first series of experiments). Power in the occipital alpha rhythm was lesser in the left hemisphere in both series of experiments. The interaction of the “experimental series” and “hemisphere” factors was significant in the temporal areas for EEG activity in the alpha2 range, where the predominant involvement of the ventral visual system on solution of both tasks corresponded to greater asymmetry in the electrical oscillations in the rapid alpha2 rhythm and its neighboring beta1 range with greater desynchronization (lesser power) on the left side. Thus, the nature of the ongoing activity is reflected in the spatial-frequency characteristics of the “background” electrical activity of the cortex.     

Filtering performance in visual working memory is improved by reducing early spatial attention to the distractors

We investigated the underlying processes that enable improving filtering irrelevant items from entering visual working memory (WM). To this end, participants performed a bilateral change‐detection task in which either targets or targets along with distractors (i.e., the filtering condition) appeared in the memory array while ERPs were recorded. In the cue‐present condition, we provided a spatial cue coupled with a temporal cue regarding where and when the distractors would appear. On some of the filtering trials, after the offset of the memory array, task‐irrelevant probes were briefly flashed either at the locations of the targets or at the locations of the distractors. This enabled measuring whether reactivating the filtering settings resulted in reducing spatial attentional resources to the distractors, allocating additional spatial attentional resources to the targets, or both, as was measured by the P1/N1 amplitude. Results revealed that, relative to the cue‐absent condition, in the cue‐present condition the P1/N1 amplitude was reduced for probes at the distractors and was similar for probes at the targets. In addition, the reduction in the P1/N1 amplitude was accompanied by a reduced filtering cost in accuracy performance in the cue‐present condition relative to the cue‐absent condition. These findings suggest that reactivating the distractor filtering settings improved filtering performance in visual WM by reducing the allocation of spatial attention to the distractors already at early processing stages, and not by allocating additional spatial attentional resources to the targets.     

Detection of geometric, but not topological, spatial transformations in 6- to 12-month-old infants in a visual exploration paradigm

Several theories of spatial orientation propose that the geometry of an environment plays a privileged role in reorientation, relative to relations between individual landmarks. Infants (N = 90) in three age groups (6, 8 1/2, and 12 months) experienced three conditions: topological, geometric, and control. A round room contained four distinctive objects in a rectangular arrangement on the inside periphery. Infants were familiarized to the array prior to a 2-min test period. In the topological condition, two objects were switched. In the geometric condition, the objects were moved to form an irregular quadrilateral. In the control condition, the array remained unchanged. Infants of 8 1/2 months and over visually explored significantly more in the geometric condition only. An initial study with adults found greater visual exploration in both geometric and topological conditions. These results are discussed in the context of current theories of spatial orientation.     

Nasal asymmetry changes during growth and development in 6- to 12-year-old children with repaired unilateral cleft lip and palate: A 3D computed tomography analysis

Repaired unilateral cleft lip and palate (UCLP) is often accompanied by the deformity and asymmetry of the nasal region. Three-dimensional analysis was performed to investigate the relationship between nasal soft- and hard-tissue asymmetries, as well as the changes in nasal asymmetry with age, among children with repaired UCLP (age: 6–12 years). Forty-seven patients were included in this study. Their computed tomography records were retrieved for analysis of the 3D asymmetry of 10 landmarks of the nasal soft and hard tissues. We observed that asymmetry was more severe in nasal hard tissues than in soft tissues, particularly in the sagittal dimension. Compared with patients aged 6–9 years old, patients aged 10 to 12 years old had significantly increased vertical asymmetry at the base of the alar groove (Gbase, p = 0.027) and the lateral point of the piriform aperture (LPA), (p < 0.001). The correlation between the LPA and the alar region was weak to moderate (r = 0.290 to 0.488). In conclusion, we found no evidence of growth and development in nasal hard-tissue asymmetry among 6- to 12-year-old children with repaired UCLP, except for the vertical dimension. Nasal soft tissue exhibited a more preferable symmetry than hard tissue, and this could be attributed to the compensatory growth of nasal soft tissue, particularly in the vertical and sagittal dimensions. The weak to moderate correlations between nasal soft-tissue asymmetry and hard-tissue asymmetry were observed in the three dimensions. Surgeons should consider these factors when repositioning the nasal alar and controlling the size of the nostrils.