AUTHOR=Branand Brittany , Mashek Debra , Aron Arthur TITLE=Pair-Bonding as Inclusion of Other in the Self: A Literature Review JOURNAL=Frontiers in Psychology VOLUME=Volume 10 - 2019 YEAR=2019 URL=https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2019.02399 DOI=10.3389/fpsyg.2019.02399 ISSN=1664-1078 ABSTRACT=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 a variety of relational concepts such as perspective taking (Bernstein, Laurent, Nelson, & Laurent, 2015), social comparison (Thai & Lockwood, 2015), self-determination (Weinstein, Rodriguez, Knee, & Kumashiro, 2016), humor (Treger, Sprecher, & Erber, 2013), and pain contagion (Martire, Keefe, Schulz, Stephens, & Mogle, 2013). Next, we explore two recent theoretical directions of the principle—the two-dimensional model of relational self-change (McIntyre, Mattingly, & Lewandowski, 2015) and the perceived inclusion of the other in the self (IOS-perceived) construct (Tomlinson & 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.