Judith Dunn

Becoming a Family Member: Family Conflict and the Development of Social Understanding in the Second Year

DUNN, JUDY, and MUNN, PENNY. Becoming a Family Member: Family Conflict and the Development of Social Understanding in the Second Year. CHILD DEVELOPMENT, 1985, 56, 480-492. The development of childrens participation in family interaction during the second year of life was examined in 2 longitudinal observational studies of family conflict in the home, focusing on 3 developmental issues: first, the development of childrens understanding of the feelings and intentions of other family members; second, their understanding of social rules within the family; and third, the relation of emotional changes to these developments in social understanding. Study 1, an intensive study of 6 mother-sibling triads observed when the second-born child was 14, 16, 18, 21, and 24 months old, examined childrens behavior in conflict with the sibling and with the mother. In Study 2, 43 families were observed when the second-born child was 18 and 24 months old. Developments in childrens teasing, their supportive and prohibiting actions, and their communication about transgressions demonstrate their increasing understanding of family members and family rules. Children were found to be differentially responsive both to emotions displayed by other family members and to the topic of family disputes.

Why are children in the same family so different? Nonshared environment a decade later.

Objective: To review recent developments in the study of nonshared environment; that is, the environmental influences that make children growing up in the same family different, rather than similar. Method: We review several recent influential books and papers on the subject of nonshared environment from the decade following the 1987 paper that highlighted its importance in psychological development. Results: Modest progress has been made toward identifying the specific aspects of the environment responsible for nonshared environment. Although parents treat their multiple children differently, such differential treatment accounts for only a small amount of nonshared environmental influence, once genetic factors are controlled. It has been suggested that some degree of nonshared environment may be due to the fact that siblings react differently to ostensibly shared environmental influences. Peer influence and other experiences outside the family may be more important sources of systematic nonshared environment. Conclusions: Despite the difficulties encountered in identifying specific sources of nonshared environment, the fact remains that most environmental variance affecting the development of psychological dimensions and psychiatric disorders is not shared by children growing up in the same family. More research and theory are needed to explain why such siblings are so different. Chance, in the sense of idiosyncratic experiences, also needs to be considered.

Nonshared Environmental Influences on Individual Differences in Early Behavioral Development: A Monozygotic Twin Differences Study

The monozygotic (MZ) twin differences method was used to investigate nonshared environmental (NSE) influences independent of genetics. Four-year-old MZ twin pairs (N = 2,353) were assessed by their parents on 2 parenting measures (harsh parental discipline and negative parental feelings) and 4 behavioral measures (anxiety, prosocial behavior, hyperactivity, and conduct problems). Within-pair differences in parenting correlated significantly with MZ differences in behavior, with an average effect size of 3%. For the extreme 10% of the parenting-discordant and behavior-discordant distributions, the average NSE effect size was substantially greater (11%), suggesting a stronger NSE relationship for more discordant twins. NSE relationships were also stronger in higher risk environments, that is, families with lower socioeconomic status, greater family chaos, or greater maternal depression.