Biomedical subjects
S Scarr
Publications and source records attributed to S Scarr.
Developmental theories for the 1990s: development and individual differences.
Understanding both typical human development and indivdual differences within the same theoretical framework has been difficult because the 2 orientations arise from different philosophical traditions. It is argued that an evolutionary perspective can unite the study of both species-typical development and individual variation. Research on determininants of development from many perspectives can be understood within an evolutionary framework in which organism and environment combine to produce development. Species-normal genes and environments and indidividual variations in genes and environments both affect personality, social, and intellectual development. These domains are used as examples to integrate theories of normal development and individual differences. Within the usual samples of European, North American, and developed Asian countries, the results of family and twin studies show that environments within the normal species range are crucial to normal development. Given a wide range of environmental opportunities and emotional supports, however, most children in these societies grow up to be individually different based on their individual genotypes. Understanding the ways in which genes and environments work together helps developmentalists to identify children in need of intervention and to tailor interventions to their particular needs.
Race and gender as psychological variables. Social and ethical issues.
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Three cheers for behavior genetics: winning the war and losing our identity.
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Reply to: The Use of Racial Admixture as Evidence in Intelligence Research. A critique by B. S. Centerwall in Hum. Genet. 45, 237-238 (1978)
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Twin method: defense of a critical assumption.
Since Galton's time, critics of the twin method have rejected the evidence of genetic differences in human behavior, because the twin method assumes that identical and fraternal pairs have equally similar environments. Twins whose genetic similarity is misperceived by themselves and others provide a critical test of the adequacy of this assumption. The relative effects of perceived and actual genetic similarity on cotwin differences in cognitive, personality, and physical development were assessed in a sample of young, adolescent twins whose genetic similarity was often misperceived. Twins' responses to questions about their own and others' judgments about their zygosity and physical similarity, and the ratings of similarity by eight judges, were used to estimate the perceived similarity of the twins. Actual zygosity was established by matching cotwins on 12 or more blood group loci. Perceived zygosity and perceived similarity by self and others were found to be insignificant biases in the twin study method.
Effect of skin color on self-esteem.
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Gene frequency estimates for samples of Black and White twins from the Philadelphia metropolitan area.
Maximum likelihood estimates of gene frequencies and their standard errors are presented for 21 blood group and serum protein polymorphisms. The observed frequencies for certain high and low frequency antigens also are reported. The data come from a sample of 399 same-sex twin pairs and two sets of triplets from the Greater Philadelphia urban region encompassing roughly five counties in southeastern Pennsylvania and three counties of southern New Jersey. Analyses are carried out separately for the four subgroups created by subdividing the sample by race and co-twin. Total sample estimates are also calculated within the two socially defined racial groups. The gene frequency estimates generally appear to be consistent with previously reported data for U.S. urban populations. The frequency of the Fy allele in the Duffy system, however, seems to be the highest value thus far published for a white population. The white sample Fy allele very well may be a heterogeneous class in which only a very small fraction is comparable to the Fy allele common in the black sample.
Absence of a relationship between degree of white ancestry and intellectual skills within a black population.
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MZ or DZ? only your blood grouping laboratory knows for sure.
Data from individual interviews, blood grouping analyses, and ratings of photographs of a large sample of adolescent twins were examined in order to assess the accuracy of zygosity determination by alternate methods. Although the accuracy of the twins themselves and of the raters was above chance, it was not sufficiently high to justify diagnosis by these methods rather than by blood grouping analyses.
Patterns of interest similarity in adoptive and biological families.
Twin studies have indicated that genetic differences among individuals also contribute to interest and personality differences among them. In this study, 114 biologically related families and 100 adoptive families were administered the Strong-Campbell Interest Inventory. The protocols of parents and their adolescent children (total N = 870) were scored on the six scales of Holland's model of interest styles (Realistic, Investigative, Artistic, Social, Enterprising, Conventional). Biological parent--child correlations ranged from -.13 to +.40, with 15 of the 24 scale correlations achieving significance; only 2 of the adoptive parent--child correlations were significant (range from -.15 to +.25). Biologically related pairs were also significantly more correlated than adoptive pairs for interest profiles. Same-sex biological siblings were more similar to each other than either opposite-sex siblings pairs or parent--child pairs. Pairs of unrelated children in the adoptive families were not too similar either on Holland's scales or the profile analysis.
Intellectual development in family constellations with adopted and natural children: a test of the Zajonc and Markus model.
A confluence model was developed by Zajonc and Markus to account for the effects of birth order, child spacing, and family size on intellectual development. the fit of the model was tested on a sample of families with biological and adopted children. Although the model fits population data very well, it fails to account for intellectual patterns within families for whom both parent and child IQ data are available. The discrepancy is discussed in terms of sources of variance within and between families that are undetected in average values for a population.