Family resemblances in serum uric acid level

There is substantial relation between individuals' serum uric acid level and their heights and weights. Even when the association of uric acid level with height/weight is partialed out, significant resemblances in uric acid level are found between biologically related persons (parents and offspring; siblings) but not between spouses. When the association of height/weight is partialed out, uric acid level does not have a significant association with measures of cognitive ability or with educational or occupational attainment.The results reported here are made possible by a 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.     

Multivariate path analysis of specific cognitive abilities in the Colorado Adoption Project: Conditional path model of assortative mating

A multivariate path model of genetic and environmental transmission employing a conditional path representation of assortative mating was fitted to specific cognitive abilities data from the Colorado Adoption Project and evaluated using a maximum-likelihood estimation procedure. In agreement with results obtained from a previous analysis of a smaller data set, significant genetic covariation among the cognitive variables was indicated and evidence for a general genetic factor was found. However, cultural transmission parameters are nonsignificant and environmental correlations among the measures are relatively small.This work was supported in part by grants from the NSF (BNS-7826204 and BNS-8200310) and from the NICHD (HD-10333, HD-18426, and HD-19802). Preparation of the paper was facilitated by Grant RR-007013-20 awarded to the University of Colorado by the Biomedical Research Support Grant Program, Division of Research Resources, National Institutes of Health.     

Differential heritability across levels of cognitive ability

Differences in heritability and shared environmentality across levels of cognitive ability were assessed in a sample of 264 twin pairs tested at 1 year of age and in subsets tested at 2 and 3 years. Using an extension of the DF multiple regression methodology for analyzing twin data, no evidence was found for a linear or quadratic effect of level of cognitive ability on estimates of heritability or shared environmentality.This research was supported in part by Grants HD-18426 and HD-19802 from the National Institute of Child Health and Human Development (NICHD) and by a grant from the John D. and Catherine T. MacArthur Foundation. Analyses of the data were facilitated by BRSG Grant RR-07013-25 awarded to the University of Colorado by the Biomedical Research Support Grant Program, Division of Research Resources, National Institutes of Health. L.R.C. is supported by Training Grant HD-07289 from NICHD and S.S.C. is supported in part by the Natural Sciences and Engineering Research Council of Canada.     

Inference about genetic correlations

In polygenic systems genetic correlations and the factors and specific genetic variances from genetic correlation matrices are often interpreted in terms of sets of genes common or specific to variables. While these inferences may indeed be true, a genetic correlation is not always sufficient evidence for the inferences. In some cases two variables with all genes in common can have low genetic correlations, and systems with only a few genes in common can have high genetic correlations. The assumptions about genic effects in polygenic systems and their effects on a genetic correlation are explicated and discussed. It is suggested that a distinction be made betweenbiological pleiotropism andstatistical pleiotropism to promote more accurate communication about the genetic associations among traits.Preparation of this paper was supported in part by NICHD Grants HD-07289, HD-10333, and HD-18426, a grant from the Spencer Foundation, and Grant RR-07013-21 awarded to the University of Colorado by the Biochemical Research Support Grant Program, Division of Research Resources, NIH.     

Direct marital assortment for cognitive and personality variables

Recent advances in linear modeling in human genetics permit the resolution of the sources of assortative mating. Using these methods we examined the multivariate assortment relationships among education, general cognitive ability, and personality traits in two large samples of spouses from the Colorado Adoption Project (N=334 couples) and the Hawaii Family Study of Cognition (N=1165 couples). Results indicate a direct pairing of mates on the basis of eductional level and general intelligence but no cross-assortment between the two. Thus, the indirect marital correlation between education in one spouse and intelligence in the other is due only to the direct pairing on education and on intelligence and to the within-person correlation between the two traits. We also found direct isomorphic assortment as well as direct cross-assortment on some personality characteristics. However, there was no cross-assortment between the personality and the cognitive domains. Results from models based on conditional path assortment parameters differ markedly from those obtained directly from observed marital correlations.This research was supported in part by Grants HD-10333, HD-18426, and HD-19802 from the National Institute of Child Health and Human Development (NICHD), by Grants BNS-7826204 and BNS-8200310 from the National Science Foundation, and by a grant from the Spencer Foundation. The paper was written while Kay Phillips and Craig Nagoshi were supported by training Grants HD-07289 from the NICHD and DA-07043 from the National Institute on Drug Abuse, respectively. Preparation of the paper was facilitated by Grant RR-07013-20 awarded to the University of Colorado by the Biomedical Research Support Grant Program, Division of Research Resources, National Institutes of Health.     

Familial resemblance for specific cognitive abilities

Measures of familial resemblance (spouse correlations, regressions of offspring on midparent, single-parent/single-child correlations, and sibling correlations) are presented for members of the two largest ethnic groups tested in the Hawaii Family Study of Cognition. Median spouse correlations (corrected for differences in test reliability) for 15 individual tests of specific cognitive abilities are 0.15 and 0.12 for Americans of European and of Japanese ancestry, respectively. With regard to the regressions of offspring on midparent value, corresponding median values are 0.50 and 0.35. Results of hierarchical multiple regression analyses, as well as the ordering of single-parent/single-child and sibling correlations, provide no evidence to support the hypothesis that spatial ability is influenced by a sex-linked, recessive gene.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 and environmental determinants of musical ability in twins

Analyses of musical ability data from the Loehlin and Nichols National Merit Scholarship study are presented. Musical ability is indexed by four measures: interest in a profession in music, performance in school, performance outside of school, and receiving honors in music. These variables pose a challenge for behavior genetic analysis since they do not conform to the assumptions of traditional linear models. For example, there is a dependent relationship between the honors and the performance variables; one cannot obtain honors without performance. Several methods were employed to deal with these relationships, and the following conclusions appeared regardless of the method used. First, twin correlations were always high, ranging from 0.44 to 0.90 in monozygotic (MZ) twins and from 0.34 to 0.83 in dizygotic (DZ) twins. Second, although there was evidence for heritable variation, the effects of common environment were almost always larger than the effects of heredity. Third, marital assortment was not of sufficient magnitude to account for these common environment effects. In the young adults in this sample, musical ability is influenced more by shared family environment than by shared genes.This research was supported in part by Grants HD-10333 and HD-18426 from the National Institute of Child Health and Human Development (NICHD). The paper was written while Hilary Coon was under the support of Training Grant HD-07289 from the NICHD. Preparation of the paper was facilitated by Grant RR-07013-20 awarded to the University of Colorado by the Biomedical Research Support Grant Program, Division of Research Resources, National Institutes of Health.     

Sex-by-generation and ethnic group-by-generation interactions in the Hawaii Family Study of Cognition

Principal component scores for members of the three largest ethnic groups tested in the Hawaii Family Study of Cognition were subjected to a 3×2×2 (ethnic group x sex x generation) analysis of variance with unequal subclass numbers. Large and highly significant sex-by-generation and ethnic group-by-generation interactions were found for measures of general and specific cognitive abilities. These results suggest the influence of cultural factors on these group differences in Hawaii.The results reported here were 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 National Science Foundation Grant GB-34720 and National Institute of Child Health and Human Development Grant HD-06669.     

The Hawaii family study of cognition: A reply

Differences in age and number of children tested per family between two ethnic groups (Americans of Japanese ancestry and Americans of European ancestry) have a trivial effect on differences in regressions of midchild on midparent for tests of specific cognitive abilities. Although the regression of offspring on midparent value is not a mathematical function of the spouse correlation, an empirical association between these two measures of familial resemblance is expected for characters with nonzero heritability. Such an association is reported for anthropometric characters. Since age effects contribute to the covariance of family members, age correction of family cognitive data is essential.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.     

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.     

A simple method of model fitting for adoption data

Traditional models used with adoption data often make strong assumptions concerning the nature of genetic transmission and assortative mating. A simple model is presented which avoids these assumptions. The model is linearized and, thus, has the further advantage that it can be used with standard statistical packages such as LISREL or EQS. The model allows tests of the internal consistency of the data, in addition to tests of the relative strength of genetic and environmental transmission parameters. To illustrate the model, measures of general cognitive ability in parents and their 7-year-old children from the Colordo Adoption Project (CAP) were fit to the model using the LISREL program. This relatively simple model may be expanded to incorporate more complex designs involving multiple measures or siblings. Although the model will not always allow constraints on the parameter estimates in more complex models, it offers a quick, flexible method for initial exploration of adoption data.This research was supported in part by Grants HD-10333 and HD-18426 from the National Institute of Child Health and Human Development (NICHD) and by Grant MH-43899 from the National Institute of Mental Health. The paper was written while Hilary Coon was under the support of training grant HD-07289 from NICHD. Preparation of the paper was facilitated by Grant RR-07013-20 awarded to the University of Colorado by the Biomedical Research Grant Program, Division of Research Resources, National Institutes of Health.     

Multivariate behavioral genetics and development: An overview

To honor Steven G. Vandenberg on the occasion of his retirement from the University of Colorado, a symposium on multivariate behavioral genetics and development was held on May 2–4, 1985. The focus of this symposium was recent advances in multivariate behavioral genetics and their importance for the analysis of developmental phenomena. Because of Vandenberg's role in foundingBehavior Genetics, as well as the subject's relevance, the organizers of this symposium elected to publish its proceedings as a special issue of this journal. The history of multivariate behavioral genetics is outlined in this introductory paper, and a synopsis of the other papers in the issue is presented.Supported in part by grants from the NICHD (HD-10333) and the MacArthur Research Network on the Transition from Infancy to Early Childhood.     

Differences between inbred strains of mice in Morris water maze performance

Four inbred strains of mice, BALB/cByJ, C3H/2Ibg, C57BL/6Ibg, and DBA/2Ibg, were tested for their learning ability in the Morris water maze. Two forms of learning were examined: cue learning, in which the mice were required to swim toward a submerged platform marked by a proximal visual cue; and place learning, in which the animals were required to use distal visual cues to find a submerged platform. C3H and BALB mice, which lack good visual acuity, were incapable of either form of learning. Both C57 and DBA mice were capable of cue learning, but DBA mice performed poorly at the place learning task. A selective impairment in place learning is typical of rats with disrupted hippocampal function. A similar impairment in DBA mice may indicate that abnormal hippocampal function exists under baseline conditions in this strain.This work was supported by AFOSR Grant 85-0369, USPHS Grant HD-07289-01, and BRSG Grants RR-07013-19 and-20 awarded by the Biomedical Research Support Grant Program, Division of Research Resources, NIH, to the University of Colorado. The principles of animal care promulgated by the Guide for the Care and Use of Laboratory Animals, DHHS Publication No. 85-23, are observed by the University of Colorado. The University of Colorado has a letter of assurance (A1609) on file with the DHHS Office of Protection from Research Risks.     

Multiple regression analysis of twin data: A model-fitting approach

The multiple regression methodology proposed by DeFries and Fulker (DF; 1985, 1988) for the analysis of twin data is compared with maximum-likelihood estimation of genetic and environmental parameters from covariance structure. Expectations for the regression coefficients from submodels omitting theh ² andc ² terms are derived. Model comparisons similar to those conducted using maximum-likelihood estimation procedures are illustrated using multiple regression. Submodels of the augmented DF model are shown to yield parameter estimates highly similar to those obtained from the traditional latent variable model. While maximum-likelihood estimation of covariance structure may be the optimal statistical method of estimating genetic and environmental parameters, the model-fitting approach we propose is a useful extension to the highly flexible and conceptually simple DF methodology.This research was supported in part by NICHD Grants HD-11681 and HD-27802. Analyses of the data were facilitated by BRSG Grant RR-07013-25 awarded to the University of Colorado by the Biomedical Research Support Grant Program, Division of Research Resources, National Institutes of Health. The article was written while the first author was supported in part by the Natural Sciences and Engineering Research Council of Canada.     

Correlations of measures of personality and of cognitive abilities within and across generations

Members of over 100 families took a battery of cognitive tests as well as various psychometric tests of personality. Analyses showed that individuals' cognitive and personality measures frequently were significantly correlated. Parent personality scale scores were significantly correlated with offspring cognition scores, and vice versa. Multiple regressions demonstrated that fathers' personality test scores substantially increased the predictability of sons' and, to a lesser extent, daughters' cognitive scores.The results reported here were made possible by the 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 by National Institute of Child Health and Human Development Grant MH 06669.     

Phenotypic assortative mating vs. social homogamy among Japanese and Chinese parents in the Hawaii Family Study of Cognition

Among the subjects of Japanese and Chinese ancestries in the parent generation in the Hawaii Family Study of Cognition were 47 pairs of siblings. Since data were available on the spouses of these siblings, this allowed for tests of whether spouse correlations of educational and occupational attainment and cognitive abilities were due to active phenotypic assortment and/or shared social background (social homogamy). Comparisons of sibling correlations, spouse correlations, and correlations between the spouse of one sibling and the spouse of the other sibling, as well as the results of model-fitting analyses, suggest that spouse correlations for education are determined by both phenotypic assortment and social homogamy, spouse correlations for occupational attainment by phenotypic assortment, and spouse correlations for verbal ability mostly by social homogamy.The results reported here were made possible by a 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.     

Familial resemblance for the Identical Blocks Test of spatial ability: No evidence for X linkage

The Identical Blocks Test of spatial ability was administered to subsamples of the two largest ethnic groups tested in the Hawaii Family Study of Cognition—Americans of European ancestry (171 families) and Americans of Japanese ancestry (98 families). Results of a hierarchical multiple regression analysis of family data and correlational analyses provided no evidence to support the hypothesis that spatial ability is influenced by a major, X-linked, recessive gene. Thus it appears that recent failures to replicate the sex-linkage pattern obtained by Stafford (1961) are not due to differences in the tests employed. We suggest that alternative explanations should be sought for the well-known sex difference in spatial ability.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. The senior author also acknowledges support by NIMH Grant MH-11167.     

Direct and indirect IQ heritability estimates: A puzzle

Direct estimates of IQ heritability based on a single family relationship such as adopted-apart relatives are often 50% greater than indirect estimates that rely on differences in correlations such as the classical twin method or nonadoptive-adoptive comparisons. Factors such as nonadditive genetic variance, assortative mating, selective placement, measurement error, age differences, and genotype-environment correlation and interaction do not obviously explain the difference between direct and indirect IQ heritability estimates. Because direct estimates are derived from separated individuals and indirect estimates are derived from individuals reared together in families, some aspect of the within-family environment seems a likely candidate but its exact nature remains to be understood.The Colorado Adoption Project is supported by grants from the National Science Foundation (BNS-86443938) and the National Institute of Child Health and Human Development (HD-10333 and HD-18426). The Texas Adoption Project has been supported by grants from the National Institute of Mental Health (MH-24280) and the National Science Foundation (BNS-8209882).     

Familial resemblance for general cognitive ability in the Hawaii family study of cognition

Familial correlations for general cognitive ability wer estimated for three ethnic groups tested in the Hawaii Family Study of Cognition (Americans of European, Japanese, and Chinese ancestry). Assuming multivariate normality of family data, separate observed covariance matrices were computed for families of different size, ethnicity, and child's gender and then equated to their expectations using a log-likelihood ratio statistic. Resulting maximum-likelihood estimates of familial correlations are highly similar to previously reported product-moment and intraclass correlations; however, standard errors for the maximum-likelihood estimates are somewhat smaller. More importantly, the estimation procedure employed in the present study facilitates tests of alternative hypotheses. Using this approach, hypotheses of homogeneity of familial correlations among the three ethnic groups and of homogeneity among the various parent-offspring correlations (mother-son, mother-daughter, father-son, father-daughter) and sibling correlations (son-daughter, son-son, and daughter-daughter) were rejected.The results reported here were made possible by the 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 NICHD Grant HD-06669. This analysis was conducted while Beth Bennett was supported by NIMH Training Grant MH-16880.     

Comparison of parent-offspring resemblance for specific cognitive abilities

A battery of cognitive ability tests identical to that used in the Hawaii Family Study was administered to a set of Caucasian families who participated in the Boulder Family Study. Resemblances between parents and offspring were compared with those from the Hawaii, Korean, and other recent family studies, using the same cognitive tests. Estimates from these studies indicate that values for parent-offspring resemblance are nonzero and fall around the midrange of possible values.This research was supported in part by Research Grant HD06648 to Dr. Steven G. Vandenberg, and in part by Training Grant MH11167 to Dr. Gerald E. McClearn, Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado.