Sociosexual Orientation Inventory

Abstract

The Sociosexual Orientation Inventory (SOI) is a seven-item psychological measure designed to quantify individual differences in willingness to engage in uncommitted sexual relationships. Developed by Simpson and Gangestad (1991), the scale integrates three distinct components of sociosexuality: past sexual behavior, anticipated future behavior, and attitudes toward casual sex. Individuals who score high on the SOI are considered to have an unrestricted sociosexual orientation, characterized by a higher number of sexual partners, frequent fantasies about extra-pair sex, and permissive attitudes toward sex without commitment.

The SOI consists of items that assess specific behaviors (e.g., number of partners in the past year, number of one-time partners), future intentions (anticipated partners), sexual fantasies (measured on a Likert-type scale), and core attitudes toward non-committal sex. All seven items are aggregated to load onto a single, higher-order factor labeled sociosexuality, providing a robust, unidimensional score ranging from 10 (maximally restricted) to 1,000 (maximally unrestricted).

Keywords

Sociosexuality, Sexual Behavior, Casual Sex, Unrestricted sociosexual orientation, Restricted sociosexual orientation, Personality, Sexual Attitudes, Mate Selection.

Authors

Jeffry A. Simpson, Steven W. Gangestad.

Purpose

The primary purpose of the SOI is to systematically measure the continuum of individual differences in socio-sexual engagement, moving beyond simple sex differences observed in early research, such as the Kinsey Reports (1948, 1953). The scale was developed to capture the significant variability in sexual attitudes and behaviors that exists within genders, rather than just between them, allowing researchers to categorize individuals based on their orientation—from highly restricted to highly unrestricted—regarding sex outside of a committed relationship.

The SOI provides a comprehensive assessment by capturing both behavioral aspects (what the individual has done and anticipates doing) and cognitive/affective aspects (fantasies and stated attitudes), offering a robust operationalization of the sociosexual construct for use in evolutionary psychology and relationship science.

Construct

The SOI measures Sociosexuality, defined as an individual’s willingness to engage in sexual activity without the necessity of commitment, emotional investment, or romantic attachment. This construct operates along a continuum:

• Individuals scoring high exhibit an unrestricted sociosexual orientation. They report a larger number of sexual partners, more one-night stands (or “hook-ups”), more frequent extra-pair fantasies, and permissive attitudes toward sex without emotional ties.

• Individuals scoring low exhibit a restricted sociosexual orientation. They report fewer partners, anticipate fewer future partners, rarely engage in one-night stands, and generally believe that sex should be reserved for loving, committed relationships.

Validity

Substantial evidence supports the validity of the SOI, encompassing convergent, discriminant, and predictive properties, often derived from the theoretical framework established by Gangestad and Simpson (1990). The scale successfully predicts real-world sexual and relationship behaviors.

In terms of convergent validity, individuals with an unrestricted orientation (relative to restricted individuals) engage in sexual activity earlier in romantic relationships, are more likely to have multiple partners concurrently, and engage in sexual relationships characterized by less investment and emotional attachment. Unrestricted individuals also score higher on other scales known to tap related constructs, such as sexual permissiveness and impersonal sex.

The SOI also demonstrates strong predictive validity in mate selection studies. Unrestricted individuals prefer partners who are more physically attractive and possess higher social status, while placing less emphasis on loyalty and kindness. Conversely, restricted individuals prioritize kindness, affection, and fidelity over physical attractiveness. In terms of discriminant validity, restricted individuals do not show appreciably lower sex drives, nor do they score higher on sexuality-based constructs that should be uncorrelated with the SOI, such as sexual satisfaction or sex guilt.

Reliability

The SOI exhibits high levels of internal consistency and stability over time. The scale is internally consistent, with the average Cronbach alpha coefficient across different samples averaging .75 (Simpson & Gangestad, 1991, 1992), indicating that the seven items consistently measure the underlying construct of sociosexuality.

The scale also demonstrates excellent test-retest reliability. Over a two-month period, the correlation coefficient was exceptionally high (r = .94), suggesting that sociosexual orientation, as measured by the SOI, is a highly stable individual difference characteristic.

Factor Analysis

The seven items of the SOI, despite covering diverse domains (past behavior, anticipated behavior, fantasy, and attitude), load onto a single, higher-order factor, which is defined as Sociosexuality. This structure confirms the construct’s unidimensional nature, suggesting that an individual’s behavioral history, future intentions, fantasies, and attitudes regarding sex without commitment are all highly correlated manifestations of the same underlying orientation.

The specific weighting scheme used in scoring (e.g., 5X for Item 1 and Item 3) is employed to approximate the scores that would result from transforming the five core components to z scores, unit-weighting, and summing them. This weighted score correlates highly (at or above .90) with a simple unit-weighting system, confirming the reliability of the scoring method while mitigating the disproportionate influence of Item 2 (future anticipated partners), which is capped at 30 in college samples.

Instrument

Test Type: Self-report Psychological Inventory

Format: Mixed-format scale combining numerical responses for behavioral items (Items 1-3) and Likert-type scales for attitudinal and fantasy items (Items 4-7). Completion time is typically brief, requiring only 1–2 minutes.

Language Available: English (Original development language); widely translated for cross-cultural research.

Population Group: General adult population, frequently used in college samples and relationship studies.

Age Group: Adults (primarily those engaged in dating and sexual relationships).

Population Details: Scores range from 10 (maximally restricted) to 1,000 (maximally unrestricted). Due to inherent gender differences (men typically score higher), researchers are advised to partial out gender effects or analyze data separately for men and women. Outlier detection is recommended, particularly if respondents report more than 20 partners for Items 1 or 2.

Test Methodology: Scoring requires Item 7 to be reverse keyed. Items 5, 6, and 7 are summed to form the attitudinal component. The final total score uses a weighted aggregation scheme: SOI = 5X (Item 1) + 1X (Item 2) + 5X (Item 3) + 4X (Item 4) + 2X (aggregate of Items 5–7).

Keywords

Sexual Psychology, Behavioral Genetics, Individual Differences, Commitment, Relationship Science, Mate Value, Sexual Fantasy.

Authors

Author ORCID Identifier: Not provided in source content.

Affiliation Email addresses: Jeffry A. Simpson: [email protected]; Steven W. Gangestad: Affiliation: University of New Mexico.

Correspondence Address: Jeffry A. Simpson, Department of Psychology, University of Minnesota, Minneapolis, MN 55455; Steven W. Gangestad, Department of Psychology, University of New Mexico, Albuquerque, NM 87131.

Permissions & Fee and Test Year

The scale was formally published and validated in 1991 (Simpson & Gangestad, 1991). As a standardized psychological instrument published in academic journals, the SOI is commonly used in non-commercial research settings. Researchers seeking to reproduce or use the scale for commercial purposes should contact the original authors, Jeffry A. Simpson or Steven W. Gangestad, for definitive permission.

Reference’s

• Gangestad, S., & Simpson, J. A. (1990). Toward an evolutionary history of female sociosexual variation. Journal of Personality, 58, 69–96.

• Kinsey, A., Pomeroy, W., & Martin, C. (1948). Sexual behavior in the human male. Philadelphia: Saunders.

• Kinsey, A., Pomeroy, W., Martin, C., & Gebhard, P. (1953). Sexual behavior in the human female. Philadelphia: Saunders.

• Simpson, J. A., & Gangestad, S. (1991). Individual differences in sociosexuality: Evidence for convergent and discriminant validity. Journal of Personality and Social Psychology, 60, 870–883.

• Simpson, J. A., & Gangestad, S. (1992). Sociosexuality and romantic partner choice. Journal of Personality, 60, 31–51.

• Simpson, J. A., Gangestad, S. W., & Biek, M. (1993). Personality and nonverbal social behavior: An ethological perspective of relationship initiation. Journal of Experimental Social Psychology, 29, 434–461.

• Simpson, J. A., Wilson, C. L., & Winterheld, H. A. (2004). Sociosexuality and romantic relationships. In J. H. Harvey, A. Wenzel, & S. Sprecher (Eds.), Handbook of sexuality in close relationships (pp. 87–112). Mahwah, NJ: Erlbaum.

Items of the Sociosexual Orientation Inventory

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way.

Please answer all of the following questions honestly. Your responses will be treated as confidential and anonymous. For the questions dealing with behavior, write your answers in the blank spaces provided. For the questions dealing with thoughts and attitudes, circle the appropriate number on the scales provided. The term “sexual intercourse” refers to genital sex.

1. With how many different partners have you had sex (sexual intercourse) within the past year?                  

2. How many different partners do you foresee yourself having sex with during the next five years? (Please give a specific, realistic

   estimate.)                  

3. With how many different partners have you had sex on one and only one occasion?                  

4. How often do you fantasize about having sex with someone other than your current dating partner (when you are in a relationship)? (Circle one.)

   1. Never

   2. Once Every Two or Three Months

   3. Once a Month

   4. Once Every Two Weeks

   5. Once a Week

   6. A Few Times Each Week

   7. Nearly Every Day

   8. At Least Once a Day

5. Sex without love is OK.

   1 2 3 4 5 6 7 8 9

   I Strongly Disagree I Strongly Agree

6. I can imagine myself being comfortable and enjoying “casual” sex with different partners.

   1 2 3 4 5 6 7 8 9

   I Strongly Disagree I Strongly Agree

7. I would have to be closely attached to someone (both emotionally and psychologically) before I could feel comfortable and fully enjoy having sex with him or her.

   1. 1. 1. 1. 1. 1. 1. 1. 1. • 1 2 3 4 5 6 7 8 9

8. I Strongly Disagree I Strongly Agree