Failing the Duck test: Reply to Barbaro, Boutwell, Barnes, and Shackelford (2017)

In this reply, we respond to the critique by Barbaro, Boutwell, Barnes, and Shackelford (2017) in regard to our recent meta-analysis of intergenerational transmission of attachment (Verhage et al., 2016). Barbaro et al. (2017) claim that the influence of shared environment on attachment decreases with age, whereas unique environmental and genetic influences increase, which they felt was disregarded in our meta-analysis. Their criticisms, we argue, are based on a misunderstanding of the core tenets of attachment theory. Barbaro et al. (2017) unify parent-offspring attachment, attachment representations, and romantic-pair attachment under the same conceptual and empirical umbrella, even though these constructs serve different behavioral systems. We show that excluding the incompatible twin data on pair bonding from their analysis undercuts their argument. Statements about the role of the shared environment in attachment beyond early childhood are highly uncertain at this point. Importantly, even if the role of the shared environment were to wane with age, its effects may still be causally important in later childhood or adult outcomes, as either an indirect factor or as a factor influencing earlier developmental outcomes.