Sociosexual Orientation Inventory (SOI)

Abstract

The Sociosexual Orientation Inventory (SOI) is a widely utilized psychological scale designed to assess an individual’s sociosexual orientation, which reflects the willingness to engage in sexual activity outside of a committed romantic relationship. Originally developed by Jeffry A. Simpson in 1998, the scale measures a continuum ranging from restricted (requiring emotional commitment for sex) to unrestricted (comfortable with casual sex). The subsequent revision, the SOI-R (Penke & Asendorpf, 2008), enhances the instrument by partitioning sociosexuality into three distinct, measurable dimensions: behavior, attitude, and desire, providing a more comprehensive tool for research in evolutionary psychology and relationship science.

Keywords

Sociosexuality, Casual sex, Mating strategies, Relationship science, Psychological assessment, SOI-R, Personality.

Authors

Jeffry A. Simpson, Lars Penke, Jens B. Asendorpf.

Purpose

The primary purpose of the SOI is to quantify stable individual differences in sociosexual orientation. This measurement serves as a critical variable in studies predicting various relationship outcomes, including commitment levels, jealousy, infidelity risk, and the pursuit of short-term versus long-term mating strategies. By capturing these differences, researchers can better understand the underlying psychological mechanisms driving human sexual and relational decisions.

The revised nine-item SOI-R was specifically developed to overcome the limitations of the original unidimensional measure. Its purpose is to allow researchers to analyze the separate contributions of actual sexual history (Behavior), permissive beliefs (Attitude), and frequency of sexual fantasies or arousal (Desire) to overall sociosexuality, thereby achieving greater precision in correlational studies.

Construct

The scale measures Sociosexuality, a trait-like predisposition that governs the degree to which an individual views sexual activity as contingent upon emotional investment and long-term commitment. Individuals scoring high (unrestricted) are comfortable with non-committed sexual encounters, while those scoring low (restricted) prioritize emotional intimacy before engaging in sex.

The SOI-R conceptualizes sociosexuality as having three distinct yet correlated factors: Behavior (past and current sexual history, particularly with one-time partners), Attitude (explicit beliefs about the acceptability of sex without love or commitment), and Desire (cognitive components such as frequency of sexual fantasies and spontaneous arousal towards non-committed partners). This multidimensional framework aligns with modern theories suggesting that mating strategies involve complex interactions between observable actions, expressed beliefs, and internal motivations.

Validity

The SOI-R demonstrates robust construct validity, particularly through its confirmed three-factor structure across diverse populations, which supports the theoretical differentiation of behavior, attitude, and desire. Studies have consistently shown that the unrestricted dimension of the SOI-R significantly predicts actual sexual behavior, including higher numbers of lifetime and recent sexual partners, and greater likelihood of engaging in casual sex.

Furthermore, the scale exhibits strong predictive validity in relationship research. Unrestricted scores correlate negatively with measures of relationship satisfaction and commitment in coupled individuals, and positively with personality traits such as extraversion and impulsivity, confirming its place as a reliable measure of individual differences in mating psychology.

Reliability

The psychometric properties of the SOI-R indicate high reliability. Internal consistency, measured using Cronbach’s alpha, is typically strong for the overall sociosexuality score, often exceeding 0.80 in various samples. This suggests that the items consistently measure the underlying construct.

The individual subscales (Behavior, Attitude, and Desire) also demonstrate acceptable levels of internal consistency, generally ranging from 0.70 to 0.80. Additionally, the SOI-R shows good test-retest reliability over short to moderate intervals, confirming that sociosexual orientation is a stable trait across time, suitable for use in longitudinal studies.

Factor Analysis

The original SOI was primarily treated as a global, unidimensional measure. However, the development of the SOI-R utilized sophisticated statistical methods, including Factor Analysis, to establish its structure. Penke and Asendorpf (2008) employed Confirmatory Factor Analysis (CFA) to validate the theoretical proposition that sociosexuality is better represented by three separate, although correlated, factors.

The successful confirmation of the three-factor model provides empirical evidence that the measurement of sociosexuality should account for the distinct facets of past behavior, current attitudes, and underlying desire, thereby enhancing the instrument’s utility and theoretical precision within psychometrics.

Instrument

Test Type: Self-report psychological inventory

Format: 9 items (SOI-R) combining three behavioral frequency questions and six attitudinal/desire items using a 9-point Likert-type scale.

Language Available: English, German (original SOI-R validation), and widely translated into dozens of languages for cross-cultural research.

Population Group: General adult population, particularly those involved in dating and relationship studies.

Age Group: Typically utilized with individuals aged 18 and older (college students and adults).

Population Details: The scale is non-clinical and is used extensively in evolutionary psychology, social psychology, and personality research to measure individual differences in mating orientation.

Test Methodology: Scores are calculated by standardizing and summing the three subscale scores (Behavior, Attitude, Desire) to create a single overall index of sociosexuality, or by analyzing the three subscales independently.

Keywords

Sociosexual orientation, Mating psychology, Relationship quality, Sexual behavior, Personality traits, Self-report measure.

Authors

Author ORCID Identifier: N/A (Information not provided in source)

Affiliation Email addresses: [email protected]

Correspondence Address: Lars Penke, University of Edinburgh, UK

Permissions & Fee and Test Year

The original Sociosexual Orientation Inventory (SOI) was published in 1998 by Simpson. The revised and preferred version, the SOI-R, was published in 2008 by Penke and Asendorpf. The instrument is widely used in academic research and is typically available for non-commercial scholarly use without charge. For specific permissions regarding commercial use or translation, researchers are advised to contact the primary corresponding author, Lars Penke.

Reference’s

The SOI and SOI-R are anchored by the following foundational publications:

• Simpson, J. A. (1998). Sociosexual Orientation Inventory. In C.M. Davis, W. L. Yarber, R. Bauserman, G. Schreer, & S. L. Davis (Eds.), Handbook of sexuality-related measures (pp. 565-566). Thousand Oaks, CA: Sage Publications.
• Penke, L., & Asendorpf, J. B. (2008). Beyond global sociosexual orientations: A more differentiated look at sociosexuality and its effects on courtship and romantic relationships. Journal of Personality and Social Psychology, 95, 1113-1135.
• Zacchilli, T. L. (2007). The Relationship Between Conflict and Communication, Sex, Relationship Satisfaction, and other Relational Variables in Dating Relationships. A Dissertation In EXPERIMENTAL PSYCHOLOGY. Texas Tech University.

The original PDF dissertation containing the instrument can be downloaded here: http://repositories.tdl.org/ttu-ir/bitstream/handle/2346/9978/Zacchilli_Tammy_Diss.pdf?sequence=1

Items of the Sociosexual Orientation Inventory (SOI)

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

1. With how many different partners have you had sex within the past 12 months?

0‚ 1‚ 2‚ 3‚ 4‚ 5-6‚ 7-9‚ 10-19‚ 20 or more

2. With how many different partners have you had sexual intercourse on one and only one occasion?

0‚ 1‚ 2‚ 3‚ 4‚ 5-6‚ 7-9‚ 10-19‚ 20 or more

3. With how many different partners have you had sexual intercourse without ha‎ving an interest in a long-term committed relationship with this person?

0‚ 1‚ 2‚ 3‚ 4‚ 5-6‚ 7-9‚ 10-19‚ 20 or more

4. Sex without love is OK.

1 □ Strongly disagree 2 □ 3 □ 4 □ 5 □ 6 □ 7 □ 8 □ Strongly agree 9 □

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

1 □ Strongly disagree 2 □ 3 □ 4 □ 5 □ 6 □ 7 □ 8 □ Strongly agree 9

6. I do not want to have sex with a person until I am sure that we will have a long-term‚ serious relationship.

1 □ Strongly disagree 2 □ 3 □ 4 □ 5 □ 6 □ 7 □ 8 □ Strongly agree 9 □

7. How often do you have fantasies about ha‎ving sex with someone you are not in a committed romantic relationship with?

□ 1 – never

□ 2 – very seldom

□ 3 – about once every two or three months

□ 4 – about once a month

□ 5 – about once every two weeks

□ 6 – about once a week

□ 7 – several times per week

□ 8 – nearly every day

□ 9 – at least once a day

8. How often do you experience sexual arousal when you are in contact with someone you are not in a committed romantic relationship with?

□ 1 – never

□ 2 – very seldom

□ 3 – about once every two or three months

□ 4 – about once a month

□ 5 – about once every two weeks

□ 6 – about once a week

□ 7 – several times per week

□ 8 – nearly every day

□ 9 – at least once a day

9. In everyday life‚ how often do you have spontaneous fantasies about ha‎ving sex with someone you have just met?

□ 1 – never

□ 2 – very seldom

□ 3 – about once every two or three months

□ 4 – about once a month

□ 5 – about once every two weeks

□ 6 – about once a week

□ 7 – several times per week

□ 8 – nearly every day

□ 9 – at least once a day