Published online by Cambridge University Press: 12 August 2005
The Sociosexual Orientation Inventory (SOI; Simpson & Gangestad 1991) is a self-report measure of individual differences in human mating strategies. Low SOI scores signify that a person is sociosexually restricted, or follows a more monogamous mating strategy. High SOI scores indicate that an individual is unrestricted, or has a more promiscuous mating strategy. As part of the International Sexuality Description Project (ISDP), the SOI was translated from English into 25 additional languages and administered to a total sample of 14,059 people across 48 nations. Responses to the SOI were used to address four main issues. First, the psychometric properties of the SOI were examined in cross-cultural perspective. The SOI possessed adequate reliability and validity both within and across a diverse range of modern cultures. Second, theories concerning the systematic distribution of sociosexuality across cultures were evaluated. Both operational sex ratios and reproductively demanding environments related in evolutionary-predicted ways to national levels of sociosexuality. Third, sex differences in sociosexuality were generally large and demonstrated cross-cultural universality across the 48 nations of the ISDP, confirming several evolutionary theories of human mating. Fourth, sex differences in sociosexuality were significantly larger when reproductive environments were demanding but were reduced to more moderate levels in cultures with more political and economic gender equality. Implications for evolutionary and social role theories of human sexuality are discussed.
1. The SOI captures individual difference variation along a single dimension ranging from restricted (i.e., more monogamous) to unrestricted (i.e., more promiscuous) mating orientations. Actual mating behavior involving formal marriage systems; rules and norms of acceptable sexual conduct; and clandestine forms of sexual expression may or may not be represented by the terms monogamous and promiscuous mating orientations. Although nearly all forms of mating behavior are likely related to sociosexual variation in some way, throughout this article references to individual differences in monogamy versus promiscuity will be limited to variability as operationalized by the SOI.
2. In this article, an emphasis is placed on Pedersen's (1991) evolutionary logic of sex ratio and human mating. Other theories of sex ratio and sexuality may make similar predictions (e.g., Guttentag & Secord 1983). However, Pedersen's views are more consistent with what is known from decades of research on animal mating systems (Hardy 2002). Pedersen's sex ratio predictions are able to explain both human and nonhuman animal mating systems, making it the more parsimonious account of sex ratio and mating behavior.
3. One factor that may weaken support for this prediction is that men's variability in sociosexuality is generally greater than women’s. This is true both within and across the cultures of the ISDP. As a result of these range-related differences, national levels of women's sociosexuality may have less potential for correlating with nation-level cultural factors than do the more variable levels of men's sociosexuality.