The Changing Genetics/Socialization Balance

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<ul><li><p>Journal of Social Issues, Vol. 41 , No. I , 1985, p p . 127-148 </p><p>The Changing Genetics/Socialization Balance </p><p>Lois Wladis Hoffman University of Michigan </p><p>My talk today has to do with a basic psychological issue, but one that inevitably has social implications. I am referring to the old heredity-environ- ment controversy which, like Frankensteins monster, often seems to be buried beneath tons of rubble, but rises again for a sequel. </p><p>There is occurring in developmental psychology a shift in the extent to which heredity or environment is seen to play the major role in the childs development. The importance of the family environment, in particular, has been questioned. In several recent journal articles, integrative research reviews, and in one entire issue of Child Development, data have been reported that provide an impressive amount of evidence for the genetic influence on intelligence, personality, and even on the environment itself-that is, the childs genetic makeup plays a major role in both eliciting the parent response and in selectively processing the environment (Scarr &amp; McCartney, 1983). Taken at face value, the case for environmental effects, except for real deprivation, looks very much weakened. </p><p>The social implications of this are considerable, for the new work is not only suggesting the presence of a genetic influence but also the absence of a general family effect. The role of the parents and of early family experience is seen as relatively unimportant. This new research is a blow for those of us who think that there is such a thing as good parenting, that good parenting can be </p><p>This presidential address to the Society for the Psychological Study of Social Issues (Division 9) was delivered at the annual meeting of the American Psychological Association in Toronto, Canada. August 1984. The first draft was prepared while I was Scholar in Residence at the Bellagio Study and Conference Center. 1 want to express my appreciation to the Rockefeller Foundation and the staff at the Center for providing this opportunity for uninterrupted work. I was also aided by my colleagues at Temple University, particularly Marsha Weinraub and Nora Newcornbe, who provided helpful comments on the earlier draft, and Susan A n d , who served as my research assistant. </p><p>Correspondence regarding this article should be addressed to Lois W. Hoffman, Department of Psychology, University of Michigan, Ann Arbor, MI 48109. </p><p>127 </p><p>~ 2 2 - 4 5 3 7 / 8 5 / 0 3 ~ - 0 1 2 7 ~ 501 I 0 19x5 The Society for the Psychological Study of Social Issues </p></li><li><p>128 Hoffman </p><p>taught, and that while parents do not treat all their children the same, there are general patterns that characterize a parenting style and children are affected by this. </p><p>Greater support has emerged for the genetic than for the environmental positior., 1 think, because the bulk of the relevant research is being conducted by behavioral geneticists who, though very sophisticated in their own area, are not familiar with environmental theory or with socialization models. </p><p>1 also feel, however, that part of the strength of their position lies in the fact that research on the effects of the family and parenting has not kept pace with other developments in psychology. I think we have become overwhelmed with the complexities of these questions, disillusioned with the oversimplified classi- cal theories, and discouraged by the problems of adequate measurement. Most of us no longer trust parent interviews as the source of data. and behavioral observa- tion techniques are expensive to use, time consuming, and involve so much of the subjects cooperation that samples are often small and selective. Work with infants has been more vigorous than with older children, but here there are problems of knowing whether the measures of infant development actually pre- dict to enduring behavior. And as for theory, with a few exceptions, there has been considerable rejection of the old, but little effort to build the new. </p><p>In this paper I want to describe the case that the behavioral geneticist has built and to criticize this work from the standpoint of a developmental psychol- ogist who has studied the effects of the family and child-rearing practices. Most of all, however, I would like to refire enthusiasm for undertaking studies that will investigate the process by which family life and parent behavior affect the child. I would like to see this new work by the behavioral geneticists serve as a challenge to develop theories, research designs, and measures that will clarify the nature of family socialization and show its effect. </p><p>Research Designs in Behavioral Genetics Studies </p><p>The recent research by the behavioral geneticists on genetic influences on intelligence, personality, and interests have typically used one of three designs: One design involves comparing the similarities between monozygotic or identi- cal twins to the similarities between dizygotic or fraternal twins. Since the former have developed from a single fertilized egg, they have identical genetics. The latter have developed from two eggs separately fertilized and thus are simply siblings born at the same time. To the behavioral geneticist, greater similarity in intelligence test or personality scale scores between identical than fraternal twins indicates a genetic effect. </p><p>A second design, a much more powerful one, obtains measures from chil- dren adopted at or near birth and compares their scores to those of biological parents, who did not interact with them, and those of adoptive parents, who </p></li><li><p>Genetics / Socialization Balance I29 </p><p>reared them. Similarlity in scores between biological parents and the offspring they did not rear suggests a genetic effect. Similarlity between the adoptive parent and the child would indicate an environmental effect-with the matching by adoption agencies sometimes having to be taken into account. </p><p>A third design is a variation of the second, but no data are obtained from the biological parents of the adopted offspring. Instead, two samples are used-onc sample of adopted families and one of biological families who are not related to the adopted families but are matched with respect to certain demographic vari- ables. Here a comparison is made between the two sets of correlations to see whether there is more parent-child and sibling similarity in the biological or in the adoptive family. </p><p>A design not used in the recent work. though it still excites popular interest, is the study of identical twins reared apart. As many of us felt even before the exposure of Cyril Burts fraudulent reports, this occurs too rarely and the sam- ples are too peculiar to make such subjects useful for research. This view is currently shared by behavioral geneticists (Scarr &amp; Kidd. 1983). </p><p>A Problem in the Twin-Study Design: thc Assiirription qf Eyurrll? Similur Environments </p><p>My present focus will be on the recent adoption research because I believe that studies comparing identical and fraternal twins are seriously flawed. In these studies the assumption is made that identical and fraternal twins have equally similar environments, and i t is only their genetics that are not equally similar. Thus, if the identical twins are more like one another than are fraternal twins on intelligence or personality measures, their greater similarity is taken as proof of a genetic effect and the difference in the size of the correlations is used for the heritability estimate. But identical twins look exactly alike. They are often mis- taken for one another. How can it be that their environment is not more similar than that of fraternal twins who may not resemble each other at all? There is abundant evidence (Hartup, 1983; Sore11 &amp; Nowak, 1981) that adults and peers, parents and siblings, respond different!y to different appearances. Good-looking children get more positive responses from their environment than do unattractive ones; height and body build influence social responses; physical similarity to one parent more than to the other affects parental responses and the childs identifica- tion. Thus, from this difference alone, same-sex fraternal twins cannot have as similar an environment as do identical twins. </p><p>In some ways, fraternal twins may actually have a less similar environment than do ordinary siblings. It is true that they share an ordinal position and have arrived at the same point in the family cycle-that is, to inexperienced or experienced parents, when the family is having economic struggles or during a period of relative financial security, during a time of stress or a period of </p></li><li><p>130 Hoffman </p><p>harmony-and in this sense have a more similar environment than more widely spaced siblings. But they are also more subject to the contrast effect that parents and other siblings impose on them. It is common for parents to think of closely spaced siblings in contrast-e.g., this is the smart one, this is the dumb one; this is the mischievous one, this is the passive one; the closeness in age leads to a comparison that results in exaggerated labels of contrast. And the children, too, partly in response and partly to establish their own sense of identity, often perceive themselves as different; they may exaggerate minor differences and may seek to develop separate interests. </p><p>In any case, there is abundant evidence that the environments of mono- zygotic twins are more similar than those of dizygotic, and most behavioral geneticists acknowledge this (Lytton, 1977; Plomin, Willerman, &amp; Loehlin, 1976; Scarr &amp; Carter-Saltzman, 1979). They hold, however, that the assumption of equally similar environments is nevertheless a valid one, and some empirical work has been undertaken to support this defense. Loehlin &amp; Nichols (1976), for example, have argued that greater environmental similarity does not increase trait similarity. In a sample of monozygotic twins, they found that certain en- vironmental variables-such as whether or not the twins shared a room, played together, or had the same teacher-did not relate to the similarity of their scores on the California Personality Inventory. Plomin, Willerman, and Loehlin ( 1976), focusing more on the degree of physical resemblance between the twins, also studied monozygotic twins (identified as monozygotic by the mothers report of their physical similarity). They found that within that group, parental reports of the twins degree of physical similarity and confusability did not relate to the parental reports of the twins degree of personality similarity. </p><p>These data, however, suggesting that differences in personality do not relate to differences in certain environmental variables or differences in physical ap- pearance for a sample of monozygotic twins, cannot be generalized to the dif- ferences between monozygotic and dizygotic twins. These same studies also show that the differences in environment and physical appearance within the monozygotic sample are much less than the differences within a dizygotic sam- ple. Failure to find an effect for the former does not mean that effects do not exist in the latter group where the environment and physical appearance differences between pairs are much greater. Furthermore, even within the monozygotic sample, the failure to disprove the null hypothesis of no difference does not mean it has been proved. It is possible that the environmental variables examined in the Loehlin and Nichols study were not the crucial ones, and total reliance in the Plomin, Willerman, and Loehlin study on parental reports is a particular weak- ness in that design. </p><p>Both Lytton (1977) and Scarr and Carter-Saltzman (1979), on the other hand, argue that while it is true monozygotic twins have more similar environ- ments than dizygotic twins, this may be because of their greater genetic sim- </p></li><li><p>Genetics / Socialization Balance 131 </p><p>ilarity. Scarr and Carter-Saltzman have attempted to defend the questioned as- sumption in the twin studies by examining the belief in zygosity, the similarity in appearance of the twins, and the similarity in cognitive and personality mea- sures. Actual zygosity related to similarity, but so did belief in zygosity, particu- larly for the personality measures. Dizygotic twins who bore a particularly close physical resemblance to each other were likely to believe they were monozygotic and were more likely to be similar on personality measures. The authors argue that the personality similarity between dizygotic twins, like the physical sim- ilarity between them, may be the cause of their error in thinking they are mono- zygotic. This interpretation is, of course, a possibility, but it is also possible that the greater physical similarity leads to a more similar environment which in turn leads to more similar personalities. Thus, this evidence, which the authors in- terpret as being supportive of the behavioral-genetics assumption, could also be seen as evidence against the assumption. That is, the environmentalist position is that monozygotic twins, because they resemble each other physically, have more similar environments and thus they are more similar in personality and possibly cognitive ability. By the same logic, dizygotic twins who also happen to resem- ble each other closely would have similar environments and therefore more similar personalities. The Scarr and Carter-Saltzman data are consistent with this possibility. Since monozygotic twins are more likely to look like each other than are dizygotic, as a group they are likely to have more similar environments. And, as already indicated, they do (Cohen, Dibble, Grawe, &amp; Pollin, 1973; Jones, 1955; Scarr, 1968). Thus, while the physical similarity is genetic, the effect of genetics on personality and cognition may be only indirect, through its effects on environment. </p><p>In summary, in the view of the environmentalists (Kamin, 1974; Lewontin, Rose, &amp; Kamin, 1984), it is because monozygotic twins look alike that they are treated alike, and because they are treated alike, they develop similar person- alities. By the same logic, fraternal twins who look alike would be treated alike, and they too would develop similar personalities. The fact that it is much more probable that monozygotic twins will look alike is exactly why their environ- ments are expected to be more similar. The assumption of equally similar en- vironments for monozygotic and dizygotic twins is thus not a sound one and the empirical efforts to defend it are not convincing. Nevertheless, the entire design of the twin studies rests on this assumption. Since the critics of the assumption believe that identical twins are more similar than fraternal twins not only in genes but also in environment, the many demonstrations that they are also more similar on cognitive abilities, personality traits, and interests do not seem to support a genetic explanation any more than an environmental explanation. As one might expect, the heritability extimates yielded by th...</p></li></ul>


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