Gene-environment interplay, or the way that genetic and environmental sources of influence collectively shape behavioral outcomes, occupies a significant portion of my research agenda. My work in this area is largely focused on better identifying sources of individual differences in responses to various environmental experiences. For example, my co-author and I examined the role of exposure to adversity in childhood and later internalizing and externalizing problems in adulthood in a nationally representative sample of siblings from the United States. The results revealed that the extent to which adversity contributed to the examined outcomes varied not only by source, but also by sex. Similarly, my co-authors and I examined the extent that genetic and environmental influences contribute to levels of self-control. Our results revealed that self-control scores closer to the median displayed greater genetic influence, but as scores moved further from the median, environmental factors became far more influential.
In addition to the concept of self-control, I have also actively attempted to use theories and methods focused on gene-environment interplay to better understand theoretical concepts popular within criminology. For example, my co-authors and I examined the extent to which exposure to delinquent peers contributes to self-reported delinquency. Our results indicated that when peer groups were more prosocial, underlying genetic influences on delinquency were greater, but as peer delinquency increased, environmental influences became far more important. Finally, my co-authors and I also outlined the continued utility of quantitative approaches focused on gene-environment interplay (and twin studies more specifically) in the post genomic era in an article and a response commentary.
Joseph A. Schwartz, Ph.D. 