Boelen, P. A. & Hout, M. van den (2010). Inclusion of other in self and break-up related grief following relationship dissolution. Journal of Loss and Trauma.
Self-expansion theory proposes that close others are included in the self as a source of self-expansion. Using data from 78 students confronted with relationship break-up, this study examined inclusion of the former partner in the self and its role in break-up related grief. Inclusion of other in self (IOS) was assessed using the IOS-Scale and a reaction-time task in which participants made "me/not me" decisions for traits that were the same vs. different for self and ex-partner. The reaction-time task replicated earlier findings that close relationships result in confusion between traits of self and other. Furthermore, findings showed that direct/explicit IOS (tapped with the IOS-Scale) but not indirect/implicit IOS (tapped with the reaction-time task) was associated with break-up related grief.