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J C Loehlin

Publications and source records attributed to J C Loehlin.

At least 19 recordsLinked to original sources
PubMed1992

Using EQS for a simple analysis of the Colorado Adoption Project data on height and intelligence.

Simple models in the general spirit of Coon et al. (1990) are fit to the Colorado Adoption Project height and intelligence data as the second step in a two-step process. In the first step, over-time data on height and IQ are reduced to level and slope parameters. In the second, these are incorporated in path models along with parental data and fitted using EQS in a multiple-group design. Some comparisons are made between EQS and LISREL for this kind of modeling.

Adoption↗
PubMed1992

An adoption and a cross-fostering study of the Minnesota Multiphasic Personality Inventory (MMPI) Psychopathic Deviate Scale.

The first of two complementary studies compared biological and adoptive parents of teenage adoptees with either higher (n = 21) or low (n = 51) MMPI Psychopathic Deviate (Pd) scale scores. In comparison to biological mothers of the low-Pd adoptees, biological mothers of the high-Pd adoptees obtained significantly higher MMPI scores on six of eight clinical scales. Fewer differences existed between the corresponding groups of adoptive mothers, but adoptive mothers of the high Pd's did obtain significantly higher scores on the Pd and Hypomania scales. Substantial genetic correspondences also existed for Harris-Lingoes content subscales, with fewer correspondences between adoptees and their adoptive mothers. There were indications that adoptive mothers of the high-Pd children had personality traits which may have made them less effective in attenuating early signs of antisocial behavior. The second study employed a cross-fostering design dividing all biological and adoptive mothers (n = 138 each) by their respective median Pd raw scores to examine effects on offspring. Results confirmed the effect of biological mother Pd score, but only a trend suggested an adoptive mother effect, with no hint of an interaction.

Adolescent↗
PubMed1990

Genetic and environmental variation on the California Psychological Inventory vector scales.

Three recently introduced vector scales for the California Psychological Inventory (CPI) were scored for the National Merit Twin Sample and subjected to a heredity-environment analysis. Confidence intervals for genetic and environmental parameters were obtained by a bootstrap method. Two of the scales, Internality (Vector 1) and Self-Realization (Vector 3), showed the substantial heritability and near-zero family environment effects typically found for personality scales, whereas Norm-Favoring (Vector 2) showed an appreciable effect of family environment and a nonsignificant heritability.

Achievement↗
PubMed1990

Heredity, environment, and personality change: evidence from the Texas Adoption Project.

Personality changes over time can be analyzed by the same twin and adoption methods used to analyze the genetic and environmental influences on a trait at a given time. Composite parent rating measures of Extra-version, Socialization, and Stability made on two occasions approximately 10 years apart on 229 adopted and 83 nonadopted children from the Texas Adoption Project were used to illustrate this point in two ways. The first was based on correlations among family members, from which it appeared that by far the chief source of individual change was neither the genes nor shared family environment, but individual experience (and/or measurement error). The second was via a path-analytic approach to changes in the means of adopted and natural children, from which it appeared that, nonetheless, the children were tending to change on the average in the direction of their genetic parents' personalities.

Adoption↗
PubMed1989

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.

Adoption↗
PubMed1989

Modeling IQ change: evidence from the Texas Adoption Project.

An analysis of genetic and environmental contributions to intellectual change was carried out by means of a path model applied to IQ data from the Texas Adoption Project, an adoption study in which children were measured on 2 occasions approximately 10 years apart. Included in the model were assortative mating, selective placement, genotype-environment correlation, a measure of socioeconomic status, and alternative hypotheses about cross-generation environmental transmission and the persistence of a trait over time. Some form of environmental transmission across generations was necessary, but either of the 2 forms tested was sufficient. The data were best fit by considering persistence over time to occur at the level of the developed trait. The effect of both genes and family environment was significant at the time of the first measurement, but only the genes made an additional contribution between the first and the second, suggesting the necessity of revising some popular stereotypes about development.

Adolescent↗
PubMed1985

Personality resemblances in adoptive families when the children are late-adolescent or adult.

Members of 220 families who had adopted one or more children from a Texas home for unwed mothers at least 14 years ago completed the California Psychological Inventory and the Thurstone Temperament Schedule. Consistent with other recent adoption studies in Minnesota and Texas, there was very little resemblance between parents and adopted children or between adoptive siblings (average correlations about .05). The presence of a biological relationship raised correlations a little, but only a little, to about .15, suggesting that much of the explanation for personality variation must lie in within-family environmental variation or nonadditive genetic effects. In an earlier study, young adopted children appeared to be better adjusted, on the average, than biological children in the same families. This was no longer true for the late-adolescents and young adults of the present study.

Adolescent↗
PubMed1979

Intellectual resemblance among adoptive adoptive and biological relatives: the Texas adoption project.

Intellectual and personality measures were available from unwed mothers who gave their children up for adoption at birth. The same or similar measures have been obtained from 300 sets of adoptive parents and all of their adopted and natural children in the Texas Adoption Project. The sample characteristics are discussed in detail, and the basic findings for IQ are presented. Initial analyses of the data on IQ suggest moderate heritabilities. Emphasis is placed on the preliminary nature of these findings.

Adolescent↗
PubMed1978

In pursuit of the "spatial gene": a family study.

Members of 192 families in the Tel Aviv area were given a battery of eight cognitive tests focusing on spatial measures but sampling verbal, numerical, and perceptual speed domains as well. The patterns of parent-child and sibling correlations gave very weak evidence, if any, for the operation of the X-linked recessive gene postulated by Stafford and others to affect performance on tasks involving spatial visualization. An analysis of male and female score distributions provided results more favorable to the X-linkage hypothesis, at least for the child generation, although suggesting that X linkage does not explain the whole male-female difference in performance on spatial tasks.

Adolescent↗
PubMed1978

Heredity-environment analyses of Jencks's IQ correlations.

Three different published heredity-environment analyses of Jencks's summary correlations for IQ have yielded strikingly different results. It is shown empirically that differences in selection of data and in computational procedures and logical inconsistencies in specifying equations are not responsible for the differences in results. Rather, the differences trace to the underlying assumptions made by the various authors. The analyses suggest that the assumptions concerning genetic dominance, assortative mating, and special twin environments were especially critical, while those regarding selective placement and different modes of environmental transmission were not.

Environment↗