The Infidelity Scale: Psychometric properties and gender invariance among Portuguese adults

Introduction: Infidelity is a breach of trust or a crossing of the boundaries of the primary relationship and it influences intimate relationships. It can be categorised as either sexual or emotional infidelity. In Portugal, there have been few studies on this subject using suitable instruments. Objective: This study aimed to analyse the factor structure, psychometric properties, and gender invariance of the Infidelity Scale (IS) in Portuguese adults. Method: The sample comprised 660 Portuguese adults (455 women and 205 men) between 18 and 79 years of age who had been unfaithful in their relationships. Results: The confirmatory analysis showed a structure with two factors (sexual and emotional infidelity), and good values for convergent and discriminant validity were found. The results displayed a satisfactory model fit and the non-invariance of the factor structure between women and men. Conclusion: This is the first Portuguese version of the IS, an instrument for the study of intimate relationships which contributes to the development of multicultural research.