Myriad films, TV series, songs, and books are devoted to the theme of love and infidelity, which is a violation of a core principle of monogamy. However, risk and protective factors of infidelity, as well as the underlying mechanisms leading to infidelity, are insufficiently understood. Monogamy denotes the mutual decision to commit to one specific partner sexually and relationally [1
], and this relationship style is widely practiced in diverse societies. Dush and Amato (2005) showed that committed and monogamous relationships are associated with increased subjective wellbeing with the measure consisting of life satisfaction, general happiness, distress symptoms, and self-esteem. Overall, the majority of people perceive monogamy to be beneficial and desirable [1
Infidelity (or synonyms thereof such as cheating or unfaithfulness) constitutes a serious issue in exclusive romantic relationships. It is negatively associated with relationship satisfaction, causes strain, and threatens the continuation of the relationship [4
]. Recent findings even point out that higher ratings of relationship quality, including relationship passion, can decrease the desire for extramarital sex [5
]. This indicates that relationship satisfaction influences the desire for extradyadic sex. Moreover, infidelity is one of the leading causes of divorce [6
]. Indeed, an association between infidelity and strain even persists after controlling for marriage quality [8
]. The prevalence of male infidelity in heterosexual couples ranges from around 20% to over 50% (e.g., [9
]). Although infidelity has been reported to be higher in men than in women [10
], some studies have questioned this perspective, revealing similar rates of infidelity for both genders [11
]. To our knowledge, no study has examined infidelity rates in Switzerland. Nevertheless, a German representative study reported the lifetime prevalence of infidelity among heterosexual men to be as high as 49% [12
]. Another study found infidelity rates of 17–32% for heterosexual men in Germany [13
]. In a German representative sample, 83% of men indicated that fidelity in general is important for their relationships [14
]. Taken together, infidelity is widespread and most people consider it to be harmful to intimate relationships.
Based on the investment model, it has been theorized and repeatedly shown that individuals in more satisfying relationships are more likely to be committed and less likely to seek alternative partners [15
]. Therefore, relationship satisfaction emerges as a crucial factor for predicting infidelity with reduced satisfaction increasing the risk of seeking alternative partners and thereby engaging in infidelity [17
]. The mate switching hypothesis focuses on the practice some individuals have, leaving one relationship and entering another, potentially even having cultivated the new partner during the past relationship [19
]. However, not every extradyadic sexual activity is committed with regard to finding a new partner. Other relationship designs, such as consensual non-monogamy, do also exist and have previously been found to be associated with better satisfaction with communication within the relationship than monogamous relationships and higher general relationship satisfaction [20
]. However, the present examination focuses on monogamous relationships since this represents the wide practice across almost all societies. Further, some studies have investigated infidelity as a construct comprised of emotional and sexual infidelity. Walsh et al. [21
] defined emotional infidelity as having “no sexual contact but a romantic emotional attachment” and sexual infidelity as “being sexually involved with a person other than their current partner”. The present investigation focuses explicitly on sexual infidelity [22
Referring back to the investment model that identified relationship satisfaction as a crucial factor in infidelity research, the transition to fatherhood and general status of being a father have emerged as potentially relevant variables. Fatherhood is generally associated with large investments in the partner relationship with regard to the often assumed role as provider for the family or his involvement in the family [23
]. However, in a considerable portion of men, fatherhood generates distress [24
]. Fatherhood has been suggested to contribute to infidelity, as indicated by the higher divorce rates among parents compared to married couples without children [25
]. For men, becoming a father is a critical life event, which causes several changes in terms of a couple’s relationship, mental health, financial and time resources, and social roles. Longitudinal studies revealed that, during the transition to fatherhood, relationship satisfaction, relationship quality, and sexual satisfaction decreased [26
]. Moreover, the literature has consistently reported that fathers often experience distress and strain, which can further decrease relationship satisfaction and lead to infidelity [28
]. Furthermore, while it has long been suggested that the transition to fatherhood increases commitment, a more recent study found no such increase, and instead reported stable levels of commitment for married couples and a decrease in commitment for cohabiting non-married couples [30
]. Importantly, in a sample comprised of relatively young unmarried individuals between the ages of 18 and 35, besides other sociodemographic variables, having a child was not related to extradyadic sexual involvement [31
]. However, due to the study design, there was a very small portion of fathers examined and no further analyses with regard to fatherhood status, infidelity, and relationship satisfaction were conducted. Other studies have examined the link between extramarital engagement and the number of children, revealing no association [32
]. However, these studies did not capture the dichotomous nature of parenthood or fatherhood status, instead implying a dose-response relation with more children assuming more infidelity, which was not supported by the data.
Importantly, the prevalence rates of infidelity describe a curvilinear association with age, showing a steady increase before reaching a peak around 50 years, followed by a gradual decline thereafter [17
]. Wiederman [35
] found the highest rates of infidelity within the past year for 30–39-year-old men, but reported overall infidelity rates in line with Greeley [17
]. The average age of Swiss men to become a father for the first time is around 35 years of age, indicating a reduced relationship satisfaction in many men during this period and an increased risk for infidelity. A national survey from the United States suggested a U-shaped association between the likelihood of extramarital sex and marital duration in men with a nadir after 18 years [34
]. Another aspect is that, due to age-related biological changes such as testosterone decline, the prevalence of sexual dysfunction increases in middle-aged and older men [36
], and pharmaceutical treatments for these sexual dysfunctions and related symptoms might increase male sexual activity and infidelity [39
]. This is important since the current study includes elderly participants. Bloom et al. [25
] further found that infidelity increases with longer relationship duration. This is particularly important because, in the face of low relationship satisfaction, partners with a child are often more hesitant to break-up than partners without children [43
]. Therefore, age and relationship duration are also important factors to consider when investigating the link between fatherhood and infidelity. However, the relation between fatherhood, infidelity, and relationship satisfaction has never before been the focus of a study.
Nevertheless, infidelity has been investigated in various forms of exclusive heterosexual romantic relationships, such as marriage and long- or short-term relationships. As such, several further potential predictors of infidelity were identified [44
]. Personality factors, such as the Big Five [45
], were related to infidelity, showing that low scores on agreeableness and conscientiousness were associated with increased rates of infidelity [46
]. In addition, increased sensation seeking and impulsivity and reduced perspective taking were identified as factors to explain engagement in infidelity [47
]. Thus, personality research on infidelity indicates that, in addition to reduced conscientiousness and agreeableness, factors such as impulsivity are relevant facilitators of unfaithful behavior. In addition, national representative survey data from the US reveal that a higher likelihood of infidelity is associated with stronger sexual interests, more permissive sexual values, lower relationship satisfaction, and greater sexual opportunities [17
]. Furthermore, in a sample of undergraduate college students, increased alcohol consumption was associated with extradyadic sexual involvement [48
]. Interestingly, in a multivariate contextual analysis in heterosexual college students, of the examined set of variables including relationship satisfaction, relationship duration, alcohol consumption, attachment styles, and symptoms of depression, only reduced relationship satisfaction and an insecure attachment style were associated with increased infidelity [18
]. Sociosexual behavior—i.e., the disposition to engage in uncommitted sexual encounters—has been shown to be associated with the likelihood to stay single or to be in a relationship [49
] and was consistently associated with infidelity [49
]. Studies uncovered that individuals who separated showed equally high sociosexual behavior as singles. Sociosexual behavior can therefore be understood as another predictor of infidelity. This is especially relevant when discussing infidelity-driven theories such as the partner switching hypothesis [19
] or the investment model [15
]. Importantly, in a previous examination conducted by our group, higher testosterone levels were identified to be associated with increased infidelity in healthy men, while relationship satisfaction, depressive and sexual symptoms, as well as alcohol consumption differed significantly between faithful and unfaithful men [52
Other studies have also examined indirect effects with regard to infidelity and related behavior as dependent variables, which is important since the present study further examines the moderating effect of fatherhood with regard to relationship satisfaction and infidelity. For example, Weiser et al. [53
] reported that parental marital status moderates the association between parental infidelity and offspring infidelity. However, Clayton [54
] investigated a moderated mediation including the moderation effect of relationship length on the indirect association of social media use, social media-related conflict, and negative relationship outcomes (such as infidelity), and were unable to confirm the moderation-mediation model. Although findings regarding infidelity and its determinants are inconsistent, relationship satisfaction emerges as the most consistent predictor of infidelity and research highlights that the risk of infidelity increased 4-fold in couples who reported low relationship satisfaction compared to couples who reported high relationship satisfaction [55
]. However, the referenced studies were comprised of heterogeneous samples including both genders or predominantly student samples in their analyses. Since gender differences are observed in infidelity rates, gender-specific analyses are needed to identify the specific predictors of infidelity for clearly defined subgroups such as healthy men.
To date, no study has investigated the association between infidelity and fatherhood in depth. Moreover, research regarding the effect of fatherhood on the association between relationship satisfaction and engaging in extradyadic sexual activities is also lacking. Based on the above, we hypothesize that extradyadic sexual involvement occurs more often in fathers than non-fathers due to the increased strain within the partner relationship and the subsequently reduced relationship satisfaction. In addition, we hypothesize that fatherhood moderates the association between relationship satisfaction and infidelity.
The present study examined the relationship between fatherhood and infidelity, as well as the effect of fatherhood on the association between relationship satisfaction and infidelity. Since infidelity is one of the leading causes of relationship termination causing severe psychological distress in many individuals [6
]. This issue is highly relevant in order to achieve a better understanding of the determinants leading to infidelity and to foster the prevention of infidelity.
The results showed increased infidelity in fathers as compared to non-fathers. This is surprising at first glance when considering the investment model, which suggests high investment and commitment for the relationship in fathers resulting in higher relationship satisfaction and a reduced risk for infidelity [15
]. Previous research also indicates no association between the number of children or parenthood and infidelity, although the available studies are either limited to non-married individuals, used the actual number of children as predictors, while none of the studies focused on fatherhood, relationship satisfaction, and infidelity [31
]. However, relationship satisfaction of the couple commonly declines as soon as the child is born [26
]. Furthermore, fathers show an increase in depressive symptoms during the first phase after birth and a residual amount of symptomatology over the first seven years of their child’s life [64
]. We argue that during this time, when the child needs a lot of the parental attention and the relationship satisfaction of the couple is challenged, men are at an increased risk for infidelity. This is supported by research showing couples transitioning to parents. For men, the frequency of sex is significantly more relevant than for women and that infrequent sex is associated with sexual and relationship dissatisfaction in men, but not women [67
]. Although, it is known that paternity has several negative consequences for the relationship and the sexual life of fathers and mothers, this is more likely in couples with small children, while couples with older children such as eight years or older do not experience the same challenges anymore and regain some of the lost relationship and sexual satisfaction [63
]. On the other hand, it has also been suggested that in couples without children, relationship satisfaction is very low, the relationship is terminated more quickly, while parents are more likely to stay together despite difficulties for the sake of the children [68
]. However, this in turn might be associated with an increased risk of infidelity in fathers during difficult relationship periods. Unnoticed needs of fathers during the transition to fatherhood may thus lead to reduced relationship satisfaction resulting in an increased risk for infidelity.
In the present study, fathers showed higher relationship satisfaction than non-fathers. This contradicted previous research, which showed reduced relationship satisfaction in couples transitioning to parents or with young children [26
]. However, our findings support a previously identified U-shaped relation between relationship satisfaction and age of the children in fathers with a decreased relationship satisfaction after birth of the first child and an increase after the child’s age of eight years [63
]. When considering the characteristics of the present sample (e.g., average age of 47.5 years, average duration of intimate relationship 13.6 years, most of the fathers fathering two or more children), it was evident that many fathers were in the later phase of fatherhood, where relationship satisfaction increased again and even surpassed the relationship satisfaction of the childless couples [70
]. Taking another perspective, extramarital sexual activities might positively influence relationship satisfaction in fathers. One could hypothesize that the higher relationship satisfaction for fathers, despite higher rates of infidelity, represents a cognitive coping mechanism to diminish cognitive dissonance after engaging in extramarital sexual activities. Moreover, a form of idealization of the family might play an important role here, since several of the included fathers were part of a study specifically focused on fatherhood [24
]. A further possible explanation for the incongruent finding is that lower sexual satisfaction within the relationship may be compensated by extradyadic sexual activity [71
]. This, in turn, might result in higher relationship satisfaction within the primary relationship due to the fulfillment of the aspired sexual activity. However, this explanation does not take into account feelings of guilt, and further research is therefore needed to clarify whether guilt has an impact on this association.
In addition, the results show a moderating effect of fatherhood on the association between relationship satisfaction and infidelity. In other words, the effect of relationship satisfaction on infidelity depends on if the participant was a father. More specifically, only in non-fathers was lower relationship satisfaction associated with increased infidelity. This effect can be interpreted according to the mate switching hypothesis, which suggests that non-fathers engage less in extradyadic sexual activities as long as the relationship is perceived as satisfying, while more quickly seeking a new partner in the face of relationship dissatisfaction [19
]. This strategy is less appealing to fathers, since changing partners would require a great deal of adaptation with regard to the children involved. Therefore, the link between relationship satisfaction and infidelity among fathers seems to dissolve. Many parent couples come to the point to ask themselves whether it is better to stay in an unsatisfying and conflictual relation for the sake of the children or to separate [68
]. And because there is no definite answer to this question, many parents decide to stay in the relationship and within this framework to satisfy their needs as good as possible, which in fathers are also often sexual needs and thus contribute to an increased risk of infidelity [67
Additionally, the results revealed a discrepancy between directly and indirectly reported infidelity, which was particularly apparent among the fathers. According to the indirect questioning, significantly more fathers had engaged in extradyadic sexual activities than non-fathers (36.6% vs. 21.8%). The reported rates of infidelity are in line with the literature. For instance, Allen et al. [72
] reported that around a quarter of married men have engaged in infidelity, with this rate rising to almost 50% in dating relationships [73
]. The findings are also consistent with a more recent study from Germany, in which heterosexual men reported infidelity rates of 49% [12
]. As most of the participants in this study were married, a rate of just over 30% was seen as representative for the investigated population of Swiss men.
Age and length of relation were positively correlated with infidelity. As the majority of the participants had been married or in a relationship for more than one year, with a mean relationship length of 13.6 years, their relationships can be considered as long-term, which has been shown to increases the risk for infidelity [25
]. Fathers and non-fathers did not significantly differ with regard to age, and fathers showed significantly longer relationship length (16.5 years vs. 10.2 years). This was likely contributed to the identified group difference with regard to infidelity. From an evolutionary perspective, higher infidelity rates in longer relationships or older age might be interpreted as a form of ensuring the passing on of genes to as many partners as possible and thus increasing evolutionary fitness. Within the evolutionary psychology framework, another interpretation may be provided by the sexual strategies theory [74
], according to which men (and women) follow distinct strategies for short- and long-term sexual relationships, which have evolved during an evolutionary process. Both sexes face different adaptive problems, which they try to solve by weighing up costs and benefits adapted to the needs of the respective situation, i.e., short- or long-term sexual mating. For instance, distress promotes more short-term mating strategies. In contrast to the evolutionary perspective, dissatisfaction and neglect are covariates of sexual motivation for infidelity [75
], which might become significantly more important in early fatherhood due to the fact that a couple might experience a shift in lifestyle and responsibilities.
Taken together, we explain the observed findings in such a way that fathers show a substantially reduced relationship satisfaction during the early phases of paternity (e.g., first seven years) and, at the same time, show an increased risk of infidelity. However, since most couples do not want to separate because of their children, this difficult time is eventually overcome followed by an increase in relationship quality and satisfaction. In addition, by raising the children as a couple, one is proud and stronger connected with each other, further leading to increased relationship satisfaction in later phases. Therefore, it will be important for future research to concomitantly map the temporal dynamics of the likelihood of infidelity [34
] and relationship satisfaction [63
] over the course of transitioning to parents and raising children to adulthood.
4.1. Limitations and Strengths
The current study had several distinct limitations and strengths. First, infidelity was only assessed with the question of engagement in extradyadic sexual activities, without defining the exact boundaries of “sexual activities”; thus, it was left to the participants’ interpretation how sexual activities are defined. Nevertheless, it is reasonable to assume that the subjective perception of the committing partner is crucial in terms of effects on relationship satisfaction and well-being. However, infidelity was also examined in an indirect way, and thus anonymously, which enabled us to control for social desirability. Furthermore, the question about infidelity did not ask whether infidelity occurred before or exactly when after the birth of the child, and also did not ask about the exact number of incidents or the amount of extradyadic sexual partners. Thus, future research needs to address this issue and capture as precise as possible the time of the extradyadic sexual activity. Another shortcoming of the study is the lack of information about the age of the children, although the number of children was assessed and added as a covariate the age of the oldest child is particularly relevant to identify the period of increased relationship strain due to the first newborn and the period when relationship satisfaction starts to increase again.
Despite these limitations, the study also had several strengths. First, to the best of our knowledge, this is the first study to explicitly focus on the topic of fatherhood, infidelity, and relationship satisfaction. Moreover, we investigated a rather large sample of 253 men, and used validated questionnaires and measurements that enables us to control for possible confounding variables. The questionnaires enabled us to specifically target potentially influencing personality traits and aspects of mental health as covariates. The relatively large sample size allowed for the generalization of the results. Finally, the study investigated indirect effects, which can be regarded as strengths, since infidelity is a complex behavior encompassing multiple aspects. Thus, the measurement of indirect effects enables deeper insights into mechanisms and is more appropriate due to the consideration of the complexity of the behavior.
This investigation extended the knowledge about infidelity, especially for fathers. Couples confronted with infidelity experience severe distress. The discovery of infidelity is a critical life event and can cause PTSD-like symptoms with increased anxiety or depression [12
]. Therefore, it is crucial to provide information about this topic within couples’ therapy. In particular, fathers or expectant fathers and their partners should be educated about relationship changes within fatherhood and the distress this might cause, in order to adequately prepare the expectant parents and prevent infidelity.