Introduction

Being single, meaning not having an intimate partner, is a common state in contemporary post-industrial societies (Klinenberg, 2012; Ortiz-Ospina, 2019). For instance, one study conducted by the Pew Research Center in the USA found that three in ten adults were single, meaning they were not married, living with a partner, or in a committed romantic relationship (source: https://www.pewresearch.org/short-reads/2023/02/08/for-valentines-day-5-facts-about-single-americans/). Many singles attribute their singlehood to a fear of commitment (Apostolou, 2017, 2019). For example, a cross-cultural study that included a large sample (N = 6822) from eight nations found that nearly 40% of the participants indicated that they were single because they feared that they will get hurt if they were to enter in a relationship (Apostolou et al., 2021). The purpose of the present study is to investigate the factors that are associated with the fear of relationship commitment and to what extent this fear is associated with singlehood. Fear of relationship commitment and singlehood could be understood within an evolutionary theoretical perspective that will be discussed first.

The Evolutionary Origins of Singlehood

Singlehood is a complex phenomenon influenced by various factors. It has been proposed that one major cause of singlehood is the mismatch between ancestral and modern conditions (Apostolou, 2015; see also Goetz et al., 2019). Specifically, mechanisms or adaptations have evolved to interact with specific aspects of the environment to increase the likelihood of passing on the genes that code for these mechanisms, referred to as fitness (Tooby & Cosmides, 1990). When environmental conditions change, selection pressures act to adjust these mechanisms to the new conditions (Irons, 1998). However, this process takes time, and organisms may find themselves with mechanisms that are not well-adapted to effectively deal with the demands of the new environment, resulting in difficulties in survival and mating. This is known as the mismatch problem (Crawford, 1998; Li et al., 2018), and it has implications for the mating domain, as there is evidence of a substantial discrepancy between ancestral and modern environments.

More specifically, anthropological, behavioral, and phylogenetic evidence suggests that in ancestral human societies, marriages were arranged, with parents selecting spouses for their children (Coontz, 2006; Walker et al., 2011). Additionally, dominant men, often through the formation of male coalitions and the use of physical force, monopolized access to women (Puts, 2016). In contrast, contemporary societies do not involve parental selection of spouses nor are individuals forced into relationships by dominant males. Instead, individuals must find mates on their own. This disparity between ancestral and modern conditions has affected various mating mechanisms, rendering them potentially ineffective in dealing with the demands of a context characterized by free mate choice. Consequently, people may experience poor mating performance and an increased likelihood of being single (Apostolou, 2015). For example, in a context where mating was arranged or forced, there was little need for good flirting skills to attract a mate, so selection forces would not have favored the development of strong flirting abilities in most people. As a result, many individuals today have poor flirting skills and encounter difficulties in attracting intimate partners in a context where good flirting skills are crucial. Consistent with this argument, a recent study conducted with a sample of Greek-speaking participants found that a significant proportion reported poor flirting skills, which, in turn, were associated with a higher probability of being single (Apostolou, 2021).

Fear of Relationship Commitment and Singlehood

Previous theoretical arguments have predominantly focused on how the mismatch problem has led to higher rates of singlehood by affecting people’s ability to attract mates (e.g., Apostolou, 2021). Still, the mismatch problem can also contribute to a higher likelihood of singlehood by generating fear of committing to an intimate relationship. Specifically, there are reasons to believe that a significant mismatch exists between ancestral and modern conditions, not only in how intimate relationships are initiated but also in how they are sustained. Firstly, in pre-industrial contexts, individual rights were not well protected, and domestic violence was tolerated. As a result, one way for men to prevent their partners from cheating or leaving them was through intimidation and physical violence. For example, among the Creek, Sioux, and Navajo Indians in North America, men would mutilate the noses of their wives in cases of discovered or suspected infidelity (Catlin, 2004). That is to say, today’s people may possess adaptations, such as high levels of aggression, which, in a post-industrial context, might have once enabled them to assert control over their partners. However, in a post-industrial context where individual rights are well-protected and aggression is not tolerated, physical abuse is more likely to result in the termination of the relationship (Amato & Previti, 2003). Furthermore, such behaviors would provoke negative emotions, which, in turn, could leave a lasting psychological impact, causing individuals to fear committing to a new relationship to avoid reexperiencing these emotions.

Additionally, in pre-industrial contexts, individuals heavily rely on their families for subsistence and protection. For instance, in hunting and gathering societies, men depend on their wives for a reliable food supply through gathering efforts, while women depend on their husbands for protection (Lee & Devore, 1968). In post-industrial societies, individuals rely on their salaries for subsistence and on the police and the army for protection. One possible consequence is that in ancestral pre-industrial contexts, personality traits that may have a negative impact on intimate relationships, such as inflexibility, may not have experienced strong negative selection because individuals were willing to overlook them due to the benefits of support and protection. As a result, these traits may have continued to be prevalent in the population, potentially giving rise to relationship difficulties (Apostolou, 2016). In turn, these difficulties can transform being in a relationship into an unpleasant experience. Such unpleasant experiences may contribute to the development of a fear of commitment in relationships.

Although more theoretical and empirical work is needed in this area, there are compelling reasons to believe that the mismatch problem has affected mating performance, with many individuals experiencing difficulties in maintaining intimate relationships. Supporting this prediction, a cross-cultural study involving 7181 participants from 14 nations found that 57% indicated that they faced difficulties in starting and/or keeping a relationship (Apostolou et al., 2023). As discussed above, poor mating performance can result in negative experiences within intimate relationships, including conflicts, infidelity, violence, jealousy, and subsequent negative emotions. These negative experiences can create a fear of committing to an intimate relationship, ultimately leading many individuals to remain single. Consistent with this argument, singles frequently report being afraid of relationship commitment when asked why they are not in an intimate relationship (Apostolou, 2017). Yet, to the best of our knowledge, no study has examined whether fear of relationship commitment predicts singlehood, as well as the factors that predict relationship commitment, which is the purpose of the current work.

The Current Research

The current research aims to test several predictions derived from the evolutionary theoretical framework. The first prediction is that mating performance (i.e., how well people do in attracting and keeping mates) will be associated with a fear of relationship commitment, with lower mating performance being associated with a higher fear of relationship commitment (H1). In turn, a higher fear of relationship commitment will be associated with a higher probability of being single (H2). This suggests that mating performance will have an indirect effect on singlehood status through fear of relationship commitment. Specifically, lower mating performance will be associated with a higher fear of relationship commitment, which, in turn, will be associated with a higher probability of being single (H3).

Previous research indicates that lower extraversion and self-esteem are associated with poorer mating performance (Apostolou et al., 2018). Accordingly, we further predict that lower extraversion and self-esteem will be associated with lower mating performance, which will be associated with a higher fear of relationship commitment, leading to an increased probability of being single (H4). Moreover, within our theoretical framework, poor relationship quality will contribute to a higher fear of relationship commitment (H5). Poor mating performance will be associated with a higher fear of relationship commitment due to poorer relationship quality (H6). Finally, we predict that low self-esteem and extraversion will be associated with low scores in mating performance, which, in turn, will be associated with poorer relationship quality, leading to a higher fear of relationship commitment (H7).

Methods

Participants

The study was conducted at a private university in the Republic of Cyprus and a private university in Turkey, utilizing an online platform. The study link was shared with friends, colleagues, family, and through social media by student research assistants who received course credit in return. A total of 453 Turkish-speaking participants took part, including 290 women, 162 men, and one participant who identified their sex as “other.” The mean age of women was 31.6 (SD = 11.3), and the mean age of men was 32.3 (SD = 13.0). Additionally, 32.1% of the participants reported being in a relationship, 27.8% were married, 17.0% indicated being voluntarily single, 10.6% were between relationships, 9.3% were involuntarily single, and 3.3% chose to classify their relationship status as “other.”

Materials

The questionnaire was in Turkish and was created using Google Forms. It consisted of six parts. In the first part, mating performance was measured using a five-item instrument developed by Apostolou et al. (2018). The instrument included items such as “I find it easy to keep a romantic relationship.” Participants recorded their answers on a five-point Likert scale (1, strongly agree; 5, strongly disagree), with a higher mean score indicating higher mating performance (Cronbach’s alpha = 0.78). The second part measured self-esteem using the Rosenberg Self-Esteem Scale, which consisted of ten items (Rosenberg, 1965). The instrument included items such as “I feel I do not have much to be proud of.” A higher mean score indicated higher self-esteem (Cronbach’s alpha = 0.88). Personality was measured in the third part using the BFI-10, which consisted of ten questions (Rammstedt & John, 2007). Items used in the instrument included (“I see myself as someone who …”) “…is generally trusting” and “…tends to be lazy.” Mean scores could range from “ −4” to “4,” with a higher number indicating a higher score in a personality dimension.

In the fourth part, a modified version of a 17-item instrument developed by Obeid et al. (2019) was employed to measure fear of relationship commitment. The item “I have a low self-confidence and low self-esteem,” was not included as it measured self-esteem, which was assessed separately. Additionally, questions specific to individuals in an intimate relationship, such as “I do not trust my partner and I am afraid to leave or be left” and “I’m afraid that I’m not good enough for my partner,” were omitted to ensure the instrument could be rated by single participants as well. In total, participants rated 14 questions such as “I fear the responsibilities of being emotionally committed” using a five-point Likert scale (1, strongly disagree; 5, strongly agree), with a higher mean score indicating a higher fear of relationship commitment (Cronbach’s alpha = 0.82).

The fifth part recorded participants’ demographic information, including biological sex, age, and relationship status. Relationship status was measured using a previously established instrument (Apostolou & Wang, 2019), which included the following categories: “in a relationship,” “married,” “involuntarily single: I want to be in a relationship, but I find it difficult to attract a mate,” “Single between-relationships: My relationship has recently ended and I have not yet found another partner,” “Prefer to be single: I am not interested in being in a relationship,” and “other.” Participants who indicated they were “in a relationship” or “married” were directed to the sixth part, where relationship quality was measured. A relationship satisfaction scale developed by Hendrick (1988) was used, consisting of seven items (e.g., In general, how satisfied are you with your relationship?) that participants rated on a five-point scale ranging from “1” (low satisfaction) to “5” (high satisfaction) (Cronbach’s alpha = 0.91). Throughout all sections, the order of presentation of each item was randomized across participants.

Data Analysis

In order to examine the predictors of fear of relationship commitment and singlehood, we conducted serial mediation analysis using SPSS version 28 and the PROCESS version 4.2 macro. The original relationship status variable was used to create a binary variable, which was then entered as the dependent variable: The three categories of singlehood were collapsed into the first category (single), while the categories of being in a relationship and being married were collapsed into the second category (in an intimate relationship). Mating performance and fear of relationship commitment were included as mediators, and personality traits (openness, conscientiousness, extraversion, agreeableness, neuroticism) and self-esteem were included as predictors (see Fig. 1). Additionally, sex and age were entered as covariates. Unstandardized indirect effects were calculated for each of the 10,000 bootstrapped samples, and the 95% confidence interval was determined by examining the indirect effects at the 2.5th and 97.5th percentiles. Furthermore, a similar serial mediation analysis was conducted with fear of relationship commitment as the dependent variable and mating performance and relationship quality as the mediators (see Fig. 2).

Fig. 1
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The figure above depicts the different pathways that a given predictor may be associated with relationship status

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Fig. 2
figure 2

The figure above depicts the different pathways that a given predictor may be associated with fear of relationship commitment

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Results

Preliminary Analysis

We calculated that 19% of the participants had a mean score in the fear of relationship commitment variable above “3.” Given the five-point Likert scale used, this number indicates how many participants experienced a relatively high fear of relationship commitment. We have also calculated that among those who indicated that they were single, the percentage was 29.5, while for those who indicated that they were in an intimate relationship, it was 11.7. In addition, we calculated the mean fear of relationship commitment to be 2.41 (SD = 0.79), and we found that 47% of the participants gave scores above this mean.

Moreover, in order to examine the effect of the fear of relationship commitment on the different types of singlehood, we performed multinomial logistic regression where the relationship status was entered as the dependent variable, fear of relationship commitment as the independent variable, and sex and age as covariates. The results indicated that there was a significant main effect of fear of relationship commitment on relationship status [Χ2(4, N = 447) = 25.14, p < 0.001]. More specifically, as indicated by the odds ratios, one unit increase in the fear of relationship commitment was associated with a 2.06 (p = 0.001, the significance was estimated on the basis of the Wald statistic) times increase in the probability of being involuntarily single than in an intimate relationship, 1.56 (p = 0.013) times increase in the probability to prefer to be single, and 2.36 (p < 0.001) times more likely to be between relationships single than in an intimate relationship.

Fear of Relationship Commitment and Singlehood

Serial mediation results indicated that there was a significant effect of mating performance on fear of relationship commitment (p < 0.001). The coefficient was −0.21 (CI95, −0.30 to −0.12), indicating that one unit increase in mating performance was associated with a −0.21 units decrease in the fear of relationship commitment (H1). From Table 1, we can see further that agreeableness had a significant effect on the fear of relationship commitment, with higher scorers reporting lower fear of relationship commitment. In addition, there was a significant effect of sex (p < 0.001), with women indicating a higher fear of relationship commitment (M = 2.53, SD = 0.81) than men (M = 2.19, SD = 0.69). Moreover, there was a significant direct effect of fear of relationship commitment on relationship status (p = 0.004). The odds ratio was 0.61 (CI95, 0.44–0.85) indicating that one unit increase in fear of relationship commitment was associated with a 39% [(1–0.61) × 100] decrease in the probability to be in an intimidate relationship than single (H2). Similarly, there was a significant direct effect of mating performance on relationship status (p < 0.001). The odds ratio was 2.69 (CI95, 1.95–3.71) indicating that one unit increase in mating performance was associated with a 169% [(1–2.69) × 100] increase in the probability to be in an intimate relationship than single.

Table 1 Direct and indirect effects of predictors on relationship status
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Furthermore, from Table 1 we can see that there was a significant indirect effect of agreeableness on relationship status through fear of relationship commitment. In particular, one unit increase in agreeableness was associated with a 4% increase in the probability to be in an intimate relationship than single, by being associated with a lower fear of relationship commitment. We can see further that there were significant indirect effects of self-esteem, extraversion, and openness on relationship status through mating performance and fear of relationship commitment. More specifically, one unit increase in self-esteem was associated with a 3% increase in the probability to be in an intimate relationship than single, by being associated with higher mating performance, which, in turn, was associated with lower fear of singlehood. Similarly, one unit increase in extraversion was associated with a 1% increase in the probability to be in an intimate relationship than single through the same path (H4). A similar indirect effect was observed for openness.

In order to estimate the indirect effect of mating performance on relationship status through fear of relationship commitment, we performed a mediation analysis as depicted in Fig. 3. Note that sex, age, personality, and self-esteem were entered as covariates. The results indicated that there was a significant indirect effect of mating performance on relationship status through fear of relationship commitment at a 0.05 level of significance. The OR was 1.12 (CI95, 1.03–1.23), indicating that, by being associated with a decrease in the fear of relationship commitment, one unit increase in mating performance was associated with a 12% increase in the probability to be in an intimate relationship than single (H3).

Fig. 3
figure 3

The figure above depicts the direct and indirect effect of mating performance on relationship status

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Relationship Quality and Fear of Relationship Commitment

Mediation analysis indicated that there was a significant effect of relationship quality on fear of relationship commitment (p < 0.001). The coefficient was negative [− 0.28 (CI95, − 0.40 to − 0.16)] indicating that poor relationship quality was associated with a higher fear of relationship commitment (H5). From Table 2, we can see that none of our predictors had an effect on relationship quality. We can see, however, that there were significant indirect effects of self-esteem and extraversion on fear of relationship commitment through mating performance and the quality of a relationship. For instance, one unit increase in self-esteem was associated with a 0.03 units decrease in fear of relationship commitment, by being associated with a higher mating performance, which, in turn, was associated with better relationship quality, which was associated with a lower fear of relationship commitment (H7).

Table 2 Direct and indirect effects of predictors on fear of relationship commitment
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Finally, in order to estimate the indirect effect of mating performance on fear of relationship commitment through relationship quality, we performed a mediation analysis as depicted in Fig. 4. Note that sex, age, personality, and self-esteem were entered as covariates. The results indicated that there was a significant indirect effect of mating performance on the fear of relationship commitment through relationship quality at the 0.05 level of significance. The coefficient was −0.08 (CI95, −0.15 to −0.02), indicating that, by being associated with better relationship quality, one unit increase in mating performance was associated with 0.08 units decrease in fear of relationship commitment (H6).

Fig. 4
figure 4

The figure above depicts the direct and indirect effect of mating performance on fear of relationship commitment

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Discussion

The current research aimed to investigate the association between fear of relationship commitment and singlehood. Our findings indicated that a higher fear of relationship commitment was linked to an increased probability of being single. Furthermore, mating performance, agreeableness, and relationship quality were associated with fear of relationship commitment. Specifically, lower scores in mating performance and agreeableness were associated with a higher fear of relationship commitment, while lower relationship quality was associated with a higher fear of relationship commitment. Additionally, our results demonstrated that higher agreeableness was associated with a higher probability of being in an intimate relationship rather than being single, as it was associated with a lower fear of relationship commitment. Moreover, we observed that higher self-esteem, extraversion, and openness were associated with higher mating performance, which, in turn, was associated with a lower fear of relationship commitment, leading to a higher probability of being in an intimate relationship rather than being single. Similarly, higher self-esteem and extraversion were associated with higher mating performance, which, in turn, was associated with higher relationship quality and lower fear of relationship commitment.

Previous research has shown that poor mating performance is associated with a higher incidence of singlehood (Apostolou & Wang, 2019). Similarly, we found a significant effect of mating performance on relationship status, with a one unit increase in mating performance being associated with an almost 170% increase in the probability of being in an intimate relationship rather than being single. However, the existing literature has not identified the specific pathways through which poor mating performance leads to singlehood. In the current research, we have identified one such pathway, which is fear of relationship commitment. Specifically, we found that lower mating performance was associated with a higher fear of relationship commitment, which, in turn, was associated with an increased probability of being single.

This finding further suggests that factors predicting mating performance could indirectly affect singlehood status. Consistent with this argument, lower self-esteem, extraversion, and openness were associated with lower mating performance, which, in turn, were associated with a higher fear of relationship commitment and a higher probability of being single. Nevertheless, the effects were relatively small, as mating performance is likely influenced by multiple factors other than personality and self-esteem, each having a small indirect effect on relationship status. Therefore, future research should focus on identifying additional factors that predict mating performance and their connection to relationship status.

Additionally, we found that agreeableness was significantly associated with the fear of relationship commitment, with higher scores in agreeableness indicating lower scores in fear of relationship commitment. Moreover, agreeableness had an indirect effect on relationship status, as higher scorers in this trait were less likely to be single due to having a lower fear of relationship commitment. One possible explanation for this finding is that individuals high in agreeableness have a greater capacity to tolerate relationship tensions and conflict, potentially minimizing the negative impact of relationship events. More research is needed to investigate this effect in more detail.

Furthermore, our study is correlational, so causality cannot be directly tested. We propose that the mismatch between ancestral and contemporary conditions has resulted in many individuals performing poorly in the mating domain and having relationships of poor quality. Consequently, negative relationship experiences have a lasting impact, leading individuals to develop a fear of committing to intimate relationships to avoid similar negative experiences. This fear of relationship commitment, in turn, contributes to higher instances of singlehood. Individuals may actively choose to stay single, experience difficulties in attracting an intimate partner, or struggle to maintain relationships that become fragile and end. Our results suggest that fear of relationship commitment predicts all three types of singlehood, but further research using longitudinal designs is needed to explore the pathways through which fear of relationship commitment leads to higher rates of singlehood. Experimental studies could also be used by priming various types of mating performance or relationship success or failure in order to examine the effects on fear of commitment and singlehood.

Our findings have implications for how people address relationship issues. Different perspectives offer various explanations for relationship strain, ranging from Freudian approaches attributing difficulties to one’s relationship with parents (Elliot, 2002) to systems psychology attributing difficulties to a system not working properly (Dallos & Vetere, 2021). The evolutionary perspective suggests that behavioral mechanisms involved in maintaining intimate relationships have evolved in contexts vastly different from the current environment, often yielding unsatisfactory outcomes. This insight could shape the approach of mental health professionals, such as clinical and counseling psychologists, in helping clients develop healthier intimate relationships. By focusing on specific factors affected by the mismatch problem, therapists can assist clients in enhancing their mating performance, leading to higher-quality intimate relationships and reduced fear of relationship commitment. Nevertheless, further research is needed to fully understand the impact of the mismatch problem on mating performance.

One limitation of our study is that it relied on self-report instruments, which are susceptible to issues such as participants giving inaccurate answers. Additionally, our sample was non-probability-based, limiting the generalizability of our results to the wider population. Furthermore, some of the relationships between variables we identified may be bidirectional. For example, low self-esteem may contribute to poor performance in the mating domain, while poor performance in the mating domain may also lead to low self-esteem. Our study design does not allow us to differentiate between these effects. Furthermore, our study focused on the effects of mating performance, personality, and self-esteem on fear of relationship commitment, but there are likely other factors at play that we did not include. Moreover, our study was conducted within the Turkish cultural context, and it is important to examine to what extent these effects hold in other cultural settings through cross-cultural research.

In conclusion, our findings shed light on the complexity of singlehood, highlighting the interconnected factors that influence an individual’s likelihood of being single. We have found mating performance, self-esteem, and extraversion were associated with fear of relationship commitment, which, in turn, was associated with singlehood. More empirical research is needed to better understand the various factors that predict singlehood through their impact on fear of relationship commitment.