Theorising the causal impacts of social frontiers: The social and psychological implications of discontinuities in the geography of residential mix

Until very recently, the question of how residents might be affected by the gradient of neighbourhood boundaries - whether these boundaries are abrupt or gradual - has remained largely absent from mainstream segregation research. Yet, theoretical and empirical findings emerging from recent studies suggest the impacts could be profound and far-reaching. This article seeks to provide a conceptual foundation for understanding such effects. We focus on the concept of 'social frontiers': spatial discontinuities in the geography of residential mix which occur when community boundaries are abrupt. Drawing on insights from cognate disciplines, we develop a theory of social frontier impacts that articulates their potential importance in limiting and shaping contact between neighbouring communities, exacerbating territorial conflict and ultimately affecting the psychological wellbeing and life course outcomes of those living at the frontier. We present our thesis as a series of propositions and corollaries, and reflect on the implications for empirical research.