@article { , title = {Measuring the closeness of relationships: a comprehensive evaluation of the 'Inclusion of the Other in the Self' scale}, abstract = {Understanding the nature and influence of social relationships is of increasing interest to behavioral economists, and behavioral scientists more generally. In turn, this creates a need for tractable, and reliable, tools for measuring fundamental aspects of social relationships. We provide a comprehensive evaluation of the 'Inclusion of the Other in the Self' (IOS) Scale, a handy pictorial tool for measuring the subjectively perceived closeness of a relationship. The tool is highly portable, very easy for subjects to understand and takes less than 1 minute to administer. Across our three online studies with a diverse adult population (n=772) we show that six different scales designed to measure relationship closeness are all highly significantly positively correlated with the IOS Scale. We then conduct a Principal Component Analysis to construct an Index of Relationship Closeness and find that it correlates very strongly (?=.85) with the IOS Scale. We conclude that the IOS Scale is a psychologically meaningful and highly reliable measure of the subjective closeness of relationships.}, doi = {10.1371/journal.pone.0129478}, eissn = {1932-6203}, issue = {6}, journal = {PLoS ONE}, publicationstatus = {Published}, publisher = {Public Library of Science}, url = {https://nottingham-repository.worktribe.com/output/754571}, volume = {10}, year = {2015}, author = {Gaechter, Simon and Starmer, Chris and Tufano, Fabio} }