Despite frequent sanctions and potentially serious consequences, extra-dyadic involvements are a relatively common phenomenon. Previously, potential links among extra-dyadic involvements and personal or interpersonal characteristics were extensively explored. However, the developmental aspects of extra-dyadic relationships have been rather overlooked to date. Here, we focus on the association between self-reported extra-dyadic tendencies and behavior, and previous experience with extra-dyadic sex in prior romantic relationships and in the primary family. We asked both members of 86 long-term cohabiting couples to complete several inventories assessing various aspects of the relationship satisfaction, sociosexuality and extra-dyadic intentions and behavior. As in previous studies, we found a lower level of overall Dyadic Adjustment and in the subscales Affectional Expression and Dyadic Consensus, in particular, among women but not men who reported extra-pair sex. Neither experience with own nor partners' infidelity in previous relationships was linked to reported extra-pair sex in the current relationship. However, men who reported their fathers but not mothers being unfaithful were also significantly more often unfaithful and showed a higher level of extra-dyadic intentions. There was no association between parental infidelity and extra-pair sex or extra-dyadic intentions in women. Our results suggest that experience of infidelity within the primary family has an impact on subsequent behavior. However, this is the case only in men. Women's extra-dyadic activities seem to be affected instead by the quality of the current relationship. Future research is needed to test the influence of ontogenetic and hereditary factors on the development of infidelity tendencies.

Introduction Research indicated that (i) vaginal orgasm consistency is associated with indices of psychological, intimate relationship, and physiological functioning, and (ii) masturbation is adversely associated with some such measures. Aim The aim of this study was to examine the association of various dyadic and masturbation behavior frequencies and percentage of female orgasms during these activities with: (i) measures of dyadic adjustment; (ii) sexual satisfaction; and (iii) compatibility perceived by both partners. Methods In a sample of 85 Czech long-term couples (aged 20–40; mean relationship length 5.4 years), both partners provided details of recent sexual behaviors and completed sexual satisfaction, Spanier dyadic adjustment, and Hurlbert sexual compatibility measures. Multiple regression analyses were used. Main Outcome Measure The association of sexual behaviors with dyadic adjustment, sexual compatibility, and satisfaction was analyzed. Results In multivariate analyses, women's dyadic adjustment is independently predicted by greater vaginal orgasm consistency and lower frequency of women's masturbation. For both sexes, sexual compatibility was independently predicted by higher frequency of penile–vaginal intercourse and greater vaginal orgasm consistency. Women's sexual satisfaction score was significantly predicted by greater vaginal orgasm consistency, frequency of partner genital stimulation, and negatively with masturbation. Men's sexual satisfaction score was significantly predicted by greater intercourse frequency and any vaginal orgasm of their female partners. Concordance of partner vaginal orgasm consistency estimates was associated with greater dyadic adjustment. Conclusions The findings suggest that specifically penile–vaginal intercourse frequency and vaginal orgasm consistency are associated with indices of greater intimate relationship adjustment, satisfaction, and compatibility of both partners, and that women's masturbation is independently inversely associated with measures of dyadic and personal function. Results are discussed in light of previous research and an evolutionary theory of vaginal orgasm.

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