Pair-Bonding as Inclusion of Other in the Self: A Literature Review

This article surveys scholarship on the self-expansion model principle of inclusion of other in the self (IOS) as it relates to long-term pair-bonding (i.e., enduring adult romantic monogamous relationships). First, we introduce the concept of IOS and then provide a brief overview of prior research. We then review compelling extensions and findings related to relational concepts such as perspective taking ( Bernstein et al., 2015 ), social comparison ( Thai and Lockwood, 2015 ), self-determination ( Weinstein et al., 2016 ), humor ( Treger et al., 2013 ), and pain contagion ( Martire et al., 2013 ). Next, we explore two recent theoretical directions of the principle—the two-dimensional model of relational self-change ( McIntyre et al., 2015 ) and the perceived inclusion of the other in the self (IOS-perceived) construct ( Tomlinson and Aron, 2013 ). Considering these findings and their relation to pair-bonding, we propose important future directions of the IOS principle of the self-expansion model.