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Biomedical subjects

J C DeFries

Publications and source records attributed to J C DeFries.

At least 91 records · Page 5Linked to original sources
PubMed1981

Cognitive ability profiles in families of reading-disabled children.

Evidence for the heterogeneity of reading disability was sought in a family study. Psychometric test data on 125 reading-disabled children (probands) and their siblings and parents were used to identify four subtypes of reading disability, each with a distinctive cognitive ability profile. The validity of this profile analysis was then assessed by applying the same classification system to profiles of affected parents and siblings of the probands. Affected siblings of probands in subtype 3 (severely impaired reading ability but normal spatial/reasoning and coding/speed) were more likely to be of the same subtype than would be expected on the basis of chance. However, no such evidence for familial transmission of specific subtypes was found in the parental data. It is suggested that family studies may provide a strong test of the heterogeneity of reading disability, and that such studies should be used to assess the validity of alternative typologies.

Adolescent↗
PubMed1980

Components of the GABA system in mice selectively bred for differences in open-field activity.

Mice selectively bred for differences in open-field activity were utilized to test the hypothesis that differences in open-field behaviour are mediated at least in part by components of the GABA system, including brain glutamic acid decarboxylase activity (V, Vmax, and Km), as well as glutamate and GABA concentrations. Enzyme velocity was found to be inversely correlated with open-field activity, but it accounted for less than 15% of the variance. Moreover, the rank order of the lines was not as predicted for a genetically correlated character and the magnitude of the differences in enzyme activity among the lines was not large. It was therefore concluded that the GABA system is not an important mediator of differences in open-field behaviour in these lines of mice.

Animals↗
PubMed1980

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.

Europe↗
PubMed1980

Genetic models of reading disability.

Test data collected on 133 reading-disabled (RD) children and their nuclear families who participated in the Colorado Family Reading Study were subjected to segregation analysis utilizing the technique of Elston and Yelverton (1975) for a continuous phenotypic measure. The possibility of genetic heterogeneity of RD was investigated by analyzing four subsets of data: all families, families with male probands, families with female probands, and families with severely affected probands. Furthermore, an analysis of the children's data was compared to that of all family members to investigate the possibility that the disorder may be manifested differently in adults. Results from the four subsets of data show that RD is etiologically heterogeneous. Compatibility with a major recessive gene for RD was demonstrated for families with female probands. Analyses of the children's data alone give results consistent with both environmental and genetic determination of RD.

Child↗
PubMed1979

Multivariate behavioral genetic analysis of twin data on scholastic abilities.

Multivariate behavioral genetic analyses may employ either genetic and environmental correlations or phenotypically standardized covariances to assess the structure of genetic and environmental influences. Correlations and phenotypically standardized covariances answer different questions--correlations are appropriate for understanding the nature of genetic and environmental influences, whereas covariances are appropriate for determining the etiology of phenotypic correlations. The ratio of the genetic and environmental covariances to the phenotypic correlation yields estimates of bivariate heritability and environmentality, measures of the extent to which observed phenotypic covariance is due to genetic and environmental influences. Multivariate analyses of genetic and environmental correlations and covariances are illustrated with twin data on scholastic abilities. Factor analyses of correlations suggest that the same set of genes affects the major areas of academic achievement and that the environmental influences are similarly structured. Analyses of phenotypically standardized covariances indicate that the structures of genetic and environmental influences as they contribute to phenotypic resemblance among scholastic abilities are both similar and simple: there are one general genetic factor and one general environmental factor. Bivariate heritabilities and environmentalities are similar in magnitude, indicating that the strong phenotypic relationship among scholastic abilities is due roughly equally o genetic and environmental influences.

Analysis of Variance↗
PubMed1978

Response to 30 generations of selection for open-field activity in laboratory mice.

High and low lines resulting from 30 generations of bidirectional selection for open-field activity have nonoverlapping distributions and more than a thirtyfold difference in mean activity. Open-field defecation scores of low-active lines are approximately 7 times higher than those of high-active lines, substantiating earlier reports of a large, negative genetic correlation between these characters. Since the selection experiment is replicated, other variables which are found to be reliably different among the high, control, and low lines are likely to be causally related to open-field activity; thus these selected lines of mice may be of use to other investigators.

Albinism↗
PubMed1978

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.

Adolescent↗
PubMed1978

Familial nature of reading disability.

An extensive psychometric test battery was administered to 125 children with a reading disability, to their parents and siblings, and to members of 125 matched control familes (N = 1,044). In addition to expected differences in spelling and reading, probands obtained significantly (P less than or equal to .01) lower scores than controls on tests of other cognitive abilities. Manifold deficits were also found in siblings and parents of probands, conclusively demonstrating the familial (genetic and/or common-family environmental) nature of the disorder.

Child↗
PubMed1977

Assortative mating by unwed biological parents of adopted children.

Analyses of data obtained from 662 unwed couples whose children were relinquished for adoption reveal that biological parents of adopted children mate assortatively. For physical characters, assortative mating of unwed parents was similar to that of wed parents; for behavior characters, however, there was less assortative mating by the unwed parents. Because assortative mating inflates estimates of genetic parameters in adoption studies, future studies should collect information on both biological parents.

Adoption↗