Considering the Multiverse of Gene-Environment Interplay

Development is complicated. Phenotypes are influenced by genetic variants, environmental experiences, and complex interconnections between these factors dynamically across the lifespan. In contrast, behavior genetic... [ view full abstract ]

Development is complicated. Phenotypes are influenced by genetic variants, environmental experiences, and complex interconnections between these factors dynamically across the lifespan. In contrast, behavior genetic decompositions give estimates of isolated and static genetic and environmental variance. Some empirical studies track how genetic and environmental influences shift across development or operate differently across context. However, even the best attempts at empirically delineating gene-environment interplay represent vast oversimplifications of the dynamic and interactive processes that likely operate to some extent. These models necessarily rely on sets of assumptions, the reasonableness of which may be either known or unknown. Potential models of parallel, sequential, and reciprocal processes of gene-environment correlation and gene-environment interaction are nearly unlimited, and vastly under-determined when considering the available data. Here, we articulate a framework for evaluating how these complex developmental processes might combine to produce results obtained under standard behavior genetic methods. It is relatively easy to identify the effect of one processes, such as active gene-environment correlation leading to genetic variance in a twin model, but it is much more difficult to say how this process plays out in relation to gene-environment interactions and how these effects might wax and wane across the lifespan. A solution to this problem will allow us to answer important questions: (1) Given a set of observed empirical trends (e.g., genetic and environmental variance estimates, stability estimates, and how they shift across the lifespan), which combinations of additive, interactive, and dynamic processes are plausible and which can be ruled out?; and (2) When does the dynamic, highly interactive nature of development ensure that the 'gloomy prospect' of unsystematic and non-replicable genetic associations with a phenotype becomes an unavoidable certainty?