The Sociosexual Orientation Inventory (SOI-R) is a 9-item self-report questionnaire designed to measure individuals differences in the tendency to have casual, uncommitted sexual relationships.
This tendency, termed sociosexuality or sociosexual orientation, is divided into three facets measured by the inventory: behavior (in terms of number of casual and changing sex partners), attitude (towards uncommitted sex) and desire (for people not in a romantic relationship).
Sociosexuality as a concept was introduced by Alfred Kinsey[2][3] to describe differences in individuals tendency to engage in uncommitted sexual relationships.
Minimal research was done until interest in the topic markedly increased when Gangestad and Simpson released their 5-item Sociosexual Orientation Inventory in 1991.
Improving on the previous Gangestad and Simpson Sociosexuality scale, the three factors appeared to make unique contributions and have discriminant validity.