This thesis includes five empirical studies examining whether family socioeconomic status (SES) amplifies or compensates for genetic propensities on educational and health outcomes, as a mechanism in the intergenerational transmission of inequalities. It focuses on how genetic associations with traits like educational attainment, cognitive and noncognitive skills, externalising behaviors, and BMI are moderated by family factors, primarily SES and parental separation, using data from the US, the Netherlands, and the UK.
The first study finds that high-SES parents in the US compensate for low genetic propensity in less selective educational outcomes (e.g., high school) and enhance it in more selective ones (e.g., graduate school). The second study reports similar compensation for low genetic propensity for cognitive skills in academic tracking in the Netherlands but no interaction for educational outcomes. The third study shows that high-SES children in the US face stronger parental separation penalties due to a lack of compensatory strategies among children with low genetic propensities for education. Lastly, the fourth and fifth studies show that genetic propensities for externalising behaviors and BMI are more strongly linked to adverse school outcomes and overweight, respectively, among low-SES individuals, highlighting the compensatory or triggering role of family SES.
This dissertation makes at least three key contributions to the literature. First, it advances our understanding of how social inequalities are transmitted across generations by showing that socioeconomic environment of the family of origin moderates genetic associations. Second, it develops a more comprehensive theoretical framework for gene-environment research by integrating social stratification theories such as the compensatory and boosting advantage models—into a field traditionally dominated by psychological models like the Scarr-Rowe hypothesis. Third, this dissertation employs a range of techniques and research designs, such as within-family or trio designs, to address the main methodological challenges currently faced in sociogenomics and gene-environment research.
Gaia Ghirardi is a sociologist and social demographer working on the intergenerational transmission of social inequalities in education and health. She is currently PhD researcher at the SPS Department of the EUI and a postdoctoral researcher in the Department of Statistical Sciences at the University of Bologna. In her PhD project, she focused on gene-environment interaction (GxE) to understand how genetic and environmental factors interact in shaping social inequality in education and health outcomes. Her PhD chapters have been published in Demography, Social Science Research, and Research in Social Stratification and Mobility.