Longitudinal Dynamics of Gene-Environment Interplay Across Cognitive Development

Twin and family studies have demonstrated that cognitive development is driven by a combination of genetic and environmental influences acting in cohort. However, the developmental processes that drive gene-environment interplay on cognitive ability remain unclear. This dissertation, structured as three distinct, yet interrelated papers, examines the longitudinal dynamics of gene-environment interplay across cognitive development. Leveraging longitudinal data from the Louisville Twin Study (collected between 3 months and 15 years of age) and novel statistical models, each study examines a different facet of gene-environment interplay. The first study explores the Flynn Effect—systematic increases in IQ scores across generations—using a multilevel, genetically informed approach. The second study is a multivariate, longitudinal investigation of interactions between the heritability of cognitive ability (G) and socioeconomic status (SES), also known as the Scarr-Rowe interaction. Finally, the third study examines developmental dynamics common to both age-related increases in the heritability of cognitive ability, also known as the Wilson Effect, and G x SES interaction. Practical and methodological implications are discussed.