The project focuses on the theory of differential susceptibility to the environment (DST) developed within evolutionary developmental psychology. DST posits that individuals vary in their neurodevelopmental plasticity to environmental influences in a “for better and for worse” manner: some are disproportionately affected by both positive and negative factors, while others are relatively unaffected by either. Even though the theory has gained traction in developmental psychology and related fields of science, it has not been subject to a comprehensive theoretical and philosophical analysis – a gap which the project seeks to fill. It will focus on three key aspects of the theory: 1) the concept of “susceptibility to the environment”; 2) the challenges of theory choice between DST and alternative theoretical frameworks; 3) the idea of developmental mismatch and the putative adaptive effects of adverse environmental exposures. The project will critically evaluate these aspects by drawing on several bodies of work: literature on developmental plasticity in evolutionary developmental biology (evo-devo) and philosophy of biology; philosophical accounts of the role of epistemic values in theory choice; and scholarship in the social sciences and cultural evolutionary theory pertaining to socioeconomic and cultural inheritance. The aim is to deliver an assessment of DST that will be relevant for practising scientists as well as philosophers of science. Moreover, since the idea of differential susceptibility has informed policy-related debates, the project will have broader societal implications.