Thinking Close: Measuring Relational Closeness as Perceived Self-Other Inclusion

As with other psychological constructs, closeness represents a significant challenge to the measurement-minded social scientist. Although the closeness that people can feel for others is undeniably palpable, it is not easily captured by the standard methods and approaches used to assess other important relationship constructs. This chapter focuses on a social psychological attempt to meet this measurement challenge, the inclusion of other in the self scale (IOS scale; Aron, Aron, & Smollan, 1992). The IOS scale has been used in research to measure closeness as conceptualized in the frame works of self-expansion (Aron & Aron, 1997) and cognitive interdependence (Agnew, 2000; Agnew, Van Lange, Rusbult, & Langston, 1998).