Susceptibility to Infidelity Instrument

Abstract

The Susceptibility to Infidelity Instrument (SII) is a psychological measure designed to assess an individual’s perceived likelihood of committing various acts of infidelity, as well as their perception of their partner’s susceptibility to such acts within a defined timeframe (typically the next year). Developed by David M. Buss and Todd K. Shackelford (1997), the instrument explores how personality traits and relationship context factors contribute to the risk of extramarital behavior. The original research linked high susceptibility to factors such as low Conscientiousness, high Narcissism, and high Psychoticism, alongside relationship issues like sexual dissatisfaction. The scale utilizes an 11-point probability rating system (0% to 100%) for six distinct types of infidelity, ranging from minor transgressions like flirting to major breaches like having a serious affair.

Keywords

Infidelity, Relationship Assessment, Marital Conflict, Extramarital Affairs, Conscientiousness, Narcissism, Psychoticism, Relationship Dissatisfaction, Psychological Measurement.

Authors

David M. Buss, Todd K. Shackelford

Purpose

The primary purpose of the Susceptibility to Infidelity Instrument is twofold: first, to quantify an individual’s self-reported probability of engaging in various levels of infidelity (e.g., emotional versus sexual). Second, and equally crucial, it measures the participant’s perception of their current partner’s likelihood of committing these same acts. This dual assessment allows researchers to explore potential discrepancies between self-perception and partner perception regarding relationship risk and vulnerability.

Furthermore, the instrument serves to investigate the underlying psychological and contextual variables that predict infidelity risk. The original study highlighted the role of specific personality characteristics, such as low levels of Conscientiousness and elevated levels of Narcissism and Psychoticism, in increasing individual susceptibility, thereby serving as a tool for empirical research into the evolutionary and personality psychology of mating strategies.

Construct

The instrument measures the psychological construct of Susceptibility to Infidelity, which is operationalized as the subjective probability that an individual or their partner will engage in one of six specified behaviors that violate relationship boundaries within a one-year period. These behaviors range in severity, forming a continuum of relational transgression, from purely emotional acts to full sexual affairs.

The scale implicitly captures several related constructs critical to relationship stability, including commitment levels and the perceived costs of relationship dissolution. By asking participants not only about the probability of the event but also the probability of ending the relationship if the event occurred, the measure taps into perceived relationship stability and the severity of perceived transgression, providing insight into the participant’s emotional investment and jealousy patterns.

Validity

Detailed validity information for the Susceptibility to Infidelity Instrument is presented in the foundational publication by Buss and Shackelford (1997). The original study established the scale’s construct validity by demonstrating significant correlations between susceptibility scores and established personality measures.

Specifically, individuals scoring high on susceptibility were found to exhibit personality profiles characterized by low Conscientiousness, high Narcissism, and high Psychoticism. These associations provide evidence that the instrument measures a theoretically coherent aspect of relationship risk rooted in individual disposition. Furthermore, the instrument demonstrated predictive validity by linking higher susceptibility scores to specific relationship contexts, such as sexual dissatisfaction and conflicts related to partner jealousy.

Reliability

As a multi-item instrument, the reliability of the Susceptibility to Infidelity Instrument is typically assessed through measures of internal consistency. While specific reliability coefficients, such as Cronbach’s alpha, are detailed in the 1997 article, the design implies a high degree of internal reliability for the overall susceptibility score, given that all six behavioral items (flirting, kissing, dating, one-night stand, brief affair, serious affair) are intended to measure varying degrees along a single continuum of relational transgression.

Researchers utilizing this instrument would also typically assess test-retest reliability to confirm the temporal stability of susceptibility estimates. However, because the measure assesses a perceived probability over the next year, the construct itself may possess inherent variability based on dynamic changes in the relationship environment.

Factor Analysis

Although the original publication does not explicitly detail a factor analysis structure in the provided source content, the six behavioral items used in the instrument suggest that a factor analysis might reveal a potentially unidimensional structure related to the overall probability of relational boundary violation. This would indicate that all forms of infidelity risk load onto a single factor.

Alternatively, consistent with much research in relationship science, a factor analysis might differentiate the items into two distinct factors based on the depth of the transgression: Emotional Infidelity Risk (e.g., flirting, passionate kissing, romantic date) and Sexual Infidelity Risk (e.g., one-night stand, brief affair, serious affair). Confirming the factor structure is essential for appropriate scoring and interpretation, particularly when comparing gender differences in reactions to emotional versus sexual jealousy.

Instrument

Test Type: Self-report scale and partner-perception rating instrument

Format: Paper-and-pencil or digital survey format utilizing 11-point Likert-style probability scales (0% to 100% in 10% increments).

Language Available: English (Original)

Population Group: Individuals in committed romantic relationships (specifically couples, often married or cohabiting).

Age Group: Adult population (typically studied in young adulthood and early marriage).

Population Details: Originally validated on individuals in the first year of marriage, focusing on the dynamic predictors of infidelity during this high-risk period.

Test Methodology: Participants rate the probability (0–100%) of 12 distinct events occurring within the next year: six events pertaining to their partner’s likelihood of infidelity and six parallel events pertaining to their own likelihood of infidelity. Additionally, participants estimate the probability of relationship dissolution (by self and partner) should the event occur.

Keywords

Relationship dissolution, Predictors of Divorce, Sexual behavior, Psychometrics, Evolutionary Psychology, Marital Stability, Personality Traits, Narcissism.

Authors

Author ORCID Identifier: N/A (Not provided in source material)

Affiliation Email addresses: N/A (Not provided in source material)

Correspondence Address: N/A (Not provided in source material)

Permissions & Fee and Test Year

The instrument was first published in 1997 by David M. Buss and Todd K. Shackelford. Standard academic permissions apply for non-commercial research use, subject to appropriate citation of the original source article.

Test Year: 1997

Reference’s

Buss, D.M., & Shackelford, T.K (1997). Susceptibility to Infidelity in the First Year of Marriage. Journal of Research in Personality, 31, 193-221.

Items of the Susceptibility to Infidelity Instrument

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

Events With Others

Instructions. Below are listed a series of events. We would like you to make three responses to each event: 1) estimate the probability or likelihood that the event would occur within the next year; 2) estimate the probability or likelihood that if the event occurred, you would end the relationship; and 3) estimate the probability that if the event occurred, your partner would end the relationship. Circle the number that best corresponds to your estimate of each of these probabilities of occurrence; then, insert estimates on following items.

• Partner flirts with a member of the opposite sex within the next year.

0%       10%     20%     30%     40%     50%     60%     70%     80%     90%     100%

Probability that event would occur

0%       10%     20%     30%     40%     50%     60%     70%     80%     90%     100%

If event occurred, probability that you would end the relationship

0%       10%     20%     30%     40%     50%     60%     70%     80%     90%     100%

If the event occurred, probability that partner would end relationship

• Partner passionately kisses a member of the opposite sex within the next year.

                    % probability that event would occur within the next year

                    % if event occurred, probability that you would end the relationship

                    % if event occurred, probability that partner would end relationship

• Partner goes out on a romantic date with someone else within the next year.

                    % probability that event would occur within the next year

                    % if event occurred, probability that you would end the relationship

                    % if event occurred, probability that partner would end relationship

• Partner has a one-night stand with someone else within the next year.

                    % probability that event would occur within the next year

                    % if event occurred, probability that you would end the relationship

                    % if event occurred, probability that partner would end relationship

• Partner has a brief affair within the next year.

                    % probability that event would occur within the next year

                    % if event occurred, probability that you would end the relationship

                    % if event occurred, probability that partner would end relationship

• Partner has a serious affair within the next year.

                    % probability that event would occur within the next year

                    % if event occurred, probability that you would end the relationship

                    % if event occurred, probability that partner would end relationship

• You flirt with a member of the opposite sex within the next year

                    % probability that event would occur within the next year

                    % if event occurred, probability that you would end the relationship

                    % if event occurred, probability that partner would end relationship

• You passionately kiss a member of the opposite sex within the next year.

                    % probability that event would occur within the next year

                    % if event occurred, probability that you would end the relationship

                    % if event occurred, probability that partner would end relationship

• You go out on a romantic date with someone else within the next year.

                    % probability that event would occur within the next year

                    % if event occurred, probability that you would end the relationship

                    % if event occurred, probability that partner would end relationship

• You have a one-night stand with someone else within the next year.

                    % probability that event would occur within the next year

                    % if event occurred, probability that you would end the relationship

                    % if event occurred, probability that partner would end relationship

• You have a brief affair within the next year.

                    % probability that event would occur within the next year

                    % if event occurred, probability that you would end the relationship

                    % if event occurred, probability that partner would end relationship

• You have a serious affair within the next year.

                    % probability that event would occur within the next year

                    % if event occurred, probability that you would end the relationship

                    % if event occurred, probability that partner would end relationship