The Longitudinal Link Between Personality and Relationship Quality in Emerging Adults: Mediation by Identity?

Relationships in Emerging Adulthood

Emerging adulthood refers to individuals between 18 and 29 years who are in the process of becoming an adult but are neither adolescents nor adults yet (Arnett et al., 2014; O’Meara & South, 2019). They have reached physical and sexual maturity but have diverse trajectories in education, occupation, and relationships. Societal changes in terms of high demands and pressures in multiple life domains, an overwhelming number of options as well as fewer direction-giving institutions enhance the complexity of this developmental period even further (Arnett et al, 2014; Bosch & Curran, 2011; Montgomery, 2005). On the one hand, emerging adults postpone adult responsibilities and are more vulnerable to mental health problems. On the other hand, these societal changes may enhance personal maturity, the development of new skills and diverse social roles (Arnett et al, 2014; Twenge et al., 2019). Given the complexity of emerging adulthood, Arnett (2014) characterized the period by five general features: instability in relationships and work, self-focus with few obligations, feeling in-between the life spans of adolescence and adulthood, possibilities and optimism for the future and identity explorations. In line with these features, the domains of occupation and close relationships (with romantic partners, family, and friends) acquire the strongest theoretical and empirical support for identity development (Erikson, 1968; Vosylis et al., 2018) and are of special salience in emerging adulthood.

Relationship quality is defined as the degree to which partners in a relationship manifest intimacy, affection and nurturance (Furmann & Buhrmester, 2010; Mirsu-Paun & Oliver, 2017). Relationship quality represents the individual´s subjective experience of how satisfied they are in their relationship (Mirsu-Paun & Oliver, 2017). Both friendships and romantic relationships are characterized by a unique interdependence and reciprocal and mutual exchange (Ryan & Deci, 2000). Nevertheless, they have slightly distinct functions. Whereas romantic relationships mainly satisfy intimacy needs and provide emotional support, friendships serve the need for social integration, feelings of worth and to a lesser degree intimacy (Barry et al., 2009). The overlapping yet unique features of friendships and romantic relationships, emphasize the importance of context-specific models of relationships (Barry et al., 2009; Wilson et al., 2015).

The Association Between Personality and Relationship Quality

Most research on personality characteristics adopts the Big Five approach, in which personality is captured by five factors labeled as Extraversion, Agreeableness, Conscientiousness, Emotional Stability (vs. Neuroticism), and Openness (Costa et al., 2019). The associations between relationship quality and the Big Five personality have been widely studied (Beck & Jackson, 2022; Bouchard et al., 1999; Holland & Roisman, 2008; Malouff et al., 2010; O’Meara & South, 2019). Two meta-analyses reported that all Big Five traits predicted higher romantic relationship satisfaction. The largest effect size was found for Emotional stability (r = .40, Bouchard et al., 1999; r = .22, Malouff et al., 2010). Significant but less strong effects were reported for Agreeableness (r = .25, Bouchard et al., 1999, r = .15, Malouff et al., 2010) and Conscientiousness (r = .17, Bouchard et al., 1999; r = .12, Malouff et al., 2010). Results concerning Extraversion are mixed and inconsistent. Whereas meta-analyses found a significant positive correlation (r = .21, Bouchard et al., 1999; r = .06, Malouff et al., 2010), Schaffhuser et al. (2014) reported that self-reported Extraversion was not related to relationship quality. Openness has consistently been found to have the smallest significant relation with satisfaction in romantic relations (r = .02, Bouchard et al., 1999; r = .03, Malouff et al., 2010; Schaffhuser et al., 2014; Watson et al., 2000). Taken together, previous results support the utility of the Big Five Model regarding intimate relationships (Bouchard et al., 1999; Malouff et al., 2010; Schaffhuser et al., 2014). However, most research is cross-sectional and focused on marital relationships and less on romantic relationships in emerging adults.

In contrast to romantic relationship quality, there is less evidence regarding associations between personality and friendship quality. The few studies that investigated quality of friendships, found that people scoring high on Agreeableness were more likely to make friends and reported more emotional support (Festa et al., 2012; Wilson et al., 2015). People scoring high on Extraversion developed more and closer friendships, and reported more positive friendship qualities (Festa et al., 2012; Wilson et al., 2015). Individuals with higher levels of Conscientiousness seemed to have their friendships reciprocated whereas persons scoring high on Emotional Stability were less likely to interpret conflicts in friendships negatively (Festa et al., 2012; Wilson et al., 2015). Individuals low on Emotional Stability showed less emotional support, and worse conflict management (Festa et al., 2012; Wagner et al., 2014). Evidence is unclear about the association between Openness and friendship quality (Demir & Weitekamp, 2007; Wilson et al., 2015; Zhou et al., 2017).

Taken together, the importance and relevance of personality traits may depend on the nature of the relationship. For instance, a person scoring low on Extraversion may prefer staying home at night, which may result in lower friendship satisfaction, but lower levels of Extraversion may not affect satisfaction of a cohabitating romantic relationship (Wilson et al., 2015). Given the unique characteristics of romantic relationships and friendships, the first and second aims of the current study were to examine the prospective longitudinal associations among the Big Five dimensions and relationship quality of romantic relationships and friendships in emerging adults 3 years later (see Figure 1; path c).OPEN IN VIEWER

The Association Between Personality and Identity Dimensions

According to McAdams et al.’s (2010; 2015) theoretical model of personality development, personality consists of the following three layers: dispositional traits, the agentic self (agency), and a narrative identity. The first layer describes core fundamental interindividual differences in terms of dispositional traits, conceptualized with the Big Five in our study. However, these traits do not explain all human interactions and behaviours. In this model, identity resides in a different layer and refers to how individuals make choices, plan their lives or strive for goals (Luyckx et al., 2014; McAdams, 2015). Consequently, personality traits are referred to as the having side of personality, whereas identity is referred to as the doing side of personality, because people shape their individual life trajectory in close interaction with the social world. Luyckx and colleagues (2008) proposed a conceptualization of identity that captures dimensions of identity commitment and exploration. Commitment is distinguished into (1) commitment making: the degree to which individuals adhere to a set of choices, and 2) identification with commitment: the extent to which these commitments become integrated in the sense of self. Exploration is captured by 3) exploration in breadth: the extent to which individuals explore various alternatives before committing to one option, 4) exploration in depth: the evaluation of the current commitments and 5) ruminative exploration: delaying identity development as individuals are not able to commit among the limitless number of opportunities (Klimstra et al., 2013; Luyckx et al., 2014).

Further, Luyckx et al. (2014) provided empirical evidence for the role of personality traits in identity development. Specifically, the Big Five consistently predicted identity dimensions in adolescence (Klimstra et al., 2013; Luyckx et al., 2014). Extraversion was positively associated with commitment making, identification with commitment, exploration in depth and negatively associated with ruminative exploration (Klimstra et al., 2013; Luyckx et al., 2012; 2014). Concerning Agreeableness and Openness, Luyckx and colleagues (2014) found a positive association among exploration in breadth and depth. Openness was also positively associated with an extensive and ruminative exploration. A positive association of Conscientiousness with both commitment processes, exploration processes and a negative association with ruminative exploration was found. Finally, Emotional Stability was negatively related to exploration in depth and ruminative exploration and positively related to identification with commitment (Luyckx et al., 2012; 2014).

The Association Between Identity Dimensions and Relationship Quality

Erikson´s theory of psychosocial development provides a theoretical foundation for life span development and draws attention to identity as an important explanatory factor in development (Erikson, 1982). Erikson suggested that individuals move through nine stages characterized by crises. Only if a particular crisis can be solved, individuals achieve a positive outcome and move to the next developmental stage (see also Beyers & Seiffge-Krenke, 2010). Specifically, a successful development throughout the adolescence stage of identity versus role confusion (Stage 5) leads to knowledge and integration of social roles, fidelity, and feelings of continuity of the self. In turn, unsuccessful or incomplete resolution may be reflected in the inability to identify with the self and social roles (Beyers & Seiffge-Krenke, 2010). Moreover, some adolescents have difficulties moving to the next stage described by intimacy versus isolation (Stage 6). These emerging adults have difficulty forming and maintaining close relationships with friends and romantic partners and may experience loneliness, isolation and fear of relationships. Successful mastery of the crisis leads to the development of close friendships and loving and intimate relationships (Beyers & Seiffge-Krenke, 2010). Hence, Erikson proposed a developmental ordering, as “the condition of twoness is that one must first become oneself” (Erikson, 1982, p. 101). Thus, identity development may act as a precondition to develop healthy and committed relationships. In line with this, Malouff and colleagues (2010) emphasized the importance of studying mediators that can explain why personality and relationship quality are related. This information may inform interventions that aim to improve relationship quality and well-being in young adults. Given the empirical evidence that personality traits, identity dimensions and relationship outcomes are interrelated in meaningful ways (Beyers & Seiffge-Krenke, 2010; Klimstra et al., 2013; Malouff et al., 2010), we investigated whether identity dimensions mediate relations between Big Five personality traits and relationship quality (see Figure 1, path a, b, c’). More specifically, exploration is an adaptive process in identity formation, necessary to develop a self-determined sense of identity (Klimstra et al., 2012). One way identity can mediate the link between personality and relationship quality may be that extraverted people are more prone to exploring not only in breadth but also in depth. Further, exploring the partner and the relationship in depth may enhance knowledge and understanding about the partner which may be beneficial for relationship quality. Another mediating effect could be that more mature individuals (higher levels of Extraversion, Agreeableness, Conscientiousness and Emotional Stability) commit themselves more easily. Schwartz and colleagues (2013) described a reciprocal association between commitment dimensions and self-esteem in emerging adulthood, which in turn influences behaviour in relationships. Hence such a stable self-system provides an important resource for interpersonal relationships because individuals may be more securely interacting with others while remaining true to their own beliefs (Barry et al., 2009) making an individual more stable and better able to deal with conflicts in relationships. Another mediating effect may be that individuals high on Openness are likely to fall in ruminative exploration because they cannot decide on options, which may influence relationships because individuals high on ruminative exploration may be more insecure in relationships.

In addition to these theoretical links, empirical research supports the link between identity and intimacy. Regarding romantic relationship quality, Bosch and Curran (2011) found that a balanced identity (i.e., engaging in commitment while retaining exploration) was associated with positive relationship quality as indicated by higher relational maintenance. In line with this, identity achievement was positively related to companionship, affection and emotional support (Barry et al., 2009). Various studies have reported that individuals with a less secure identity (low commitment and exploration, high ruminative exploration) had a stronger tendency for conflict, higher social anxiety and reported less mature romantic relationships (Bosch & Curran, 2011; Kerpelman et al., 2008). Taken together, the link between identity dimensions and romantic relationship quality is quite well established but all studies conceptualize identity differently (Barry et al., 2009; Bosch & Curran, 2011; Kerpelman et al., 2008) which makes a comparison difficult. To the best of our knowledge, literature is scarce about the longitudinal associations between identity capturing the different dimensions of commitment and exploration (Luyckx et al., 2014) and romantic relationship quality. Therefore, the third aim of this study was to examine whether identity dimensions mediate the link between personality and relationship quality in romantic relationships (see Figure 1). Concerning friendship quality, studies that focused on relations between global identity dimensions and friendship quality in emerging adulthood are scarce and results are inconsistent. Johnson and colleagues (2007) reported a positive association between identity commitment and emotional closeness in same-sex friendships. Barry et al. (2009) found no association among identity achievement (high commitment and exploration) or foreclosure (high commitment, low exploration) and friendship qualities. Given these inconsistencies, the fourth aim of the current study was to investigate whether identity dimensions mediate the link among personality traits and relationship quality in friendships.

With regard to identity there is on ongoing discussion about the utility of global and domain specific assessment of identity in emerging adulthood (Vosylis et al., 2018). Nevertheless, in our sample of emerging adults, general future plans are central for identity formation. Hence, this study will provide information on whether satisfaction with relationships can be explained by a global identity measurement.

The Current Study

Based on the described theoretical framework, the current study investigated the longitudinal direct effects of Big Five personality traits I) on romantic relationship quality and II) on friendship quality in emerging adults. Further we tested whether identity dimensions mediate the longitudinal relationship between personality and III) romantic relationship quality and IV) friendship quality (see Figure 1) in emerging adults. Treating emerging adults as adolescents underestimates their capacities for independence, self-direction and -reflection, but seeing them as adults ignores the instability and uncertainty they experience (Arnett et al., 2014). Given the complexity of this life period and the high prevalence of psychiatric disorders in emerging adulthood (Arnett et al., 2014; Twenge et al, 2019), the present study focused on the crucial developmental period of emerging adulthood. The following hypotheses were proposed:

I & II) Based on reviewed literature, we hypothesized Extraversion, Agreeableness, Conscientiousness, Emotional Stability and Openness to be positively associated with romantic relationship quality and friendship quality in emerging adults. In line with Wilson et al. (2015), we hypothesized the effect of Emotional Stability to be more pronounced in romantic relationship quality, because people are less likely to engage in conflicts and interpret these conflicts negatively. We hypothesized that the effect of Extraversion would be more evident in friendship quality due to the positive affect and sociable character of individuals high on Extraversion, resulting in outgoing and social behavior that is more beneficial in friendships than in romantic relationships (Schaffhuser et al., 2014; Wilson et al., 2015) (Figure 1; path c). Regarding the association between Openness to Experience, and relationship quality, results are inconsistent. Openness to Experience is the most debated and least understood Big Five trait, nevertheless, our findings can add to the ongoing debate about Openness (Demir & Weitekamp, 2007; McCrae & Costa, 2008; Wilson et al., 2015; Zhou et al., 2017).

III & IV) Based on the reviewed literature (Beyers & Seiffge-Krenke, 2010; Klimstra et al., 2013; Malouff et al., 2010), we hypothesized identity dimensions to mediate the longitudinal relationship among personality traits and romantic relationship quality and friendship quality (Figure 1, path c’). In particular, and in line with the study by Luyckx et al. (2014), we hypothesized Extraversion, Agreeableness, Conscientiousness, Emotional Stability and Openness to be positively related to commitment and exploration dimensions and negatively to ruminative exploration in emerging adults (Figure 1; path a). Further, we hypothesized the identity dimensions commitment making, identification with commitment, exploration in breadth and depth to be positively related to friendship and romantic relationship quality (Figure 1; path b) (Barry et al., 2009). In contrast, ruminative exploration was expected to be negatively related to both friendship and romantic relationship quality.

Participants and Procedure

The study was conducted within the Flemish Study on Parenting, Personality and Development (FSPPD). This ongoing longitudinal study started in 1999 (for a detailed description of the recruitment of participants, see Prinzie et al., 2003; 2010). All participants provided written informed consent. For the present study, participants completed self-report questionnaires on personality and identity in Wave 8 (2015). The relationship quality was measured in Wave 9 (2018).

The total sample size was N = 372 (205, 55% females), N = 213 (57% of total sample) of them were in a romantic relationship. All participants were native Belgians and of mixed educational backgrounds. At wave eight (2015), the participants were between 18.9 and 24.2 years old, (M = 21.90 years, SD = 1.16). More demographic statistics are presented in Appendix A (Table A.1 and A.2). Little’s MCAR test (1988) indicated that, for romantic relationship quality missing values were completely at random (χ2 (11) = 17.69, p = .09), for friendship missing values were not missing completely at random (χ2 (21) = 41.4, p = .005). Full information likelihood (FIML) was used to consider missing data.

Materials

Item examples for all variables are presented in Appendix B.

Statistical Analyses

First, descriptive statistics were calculated using SPSS 26 (IBM Corp., 2019). To answer our aims, we performed multivariate mediation analysis, using a bootstrap procedure (with N = 10,000 bootstrap samples; Alfons et al., 2022) in Mplus 8.8 (Muthén & Muthén, 2007). We tested a multivariate model with romantic relationship quality and friendship relationship quality as outcome measures, the Big Five domains as predictors and the five identity dimensions as mediators (see Figure 1). Age, sex, educational level, and living situation (living with parents/living without parents) were included as covariates in the model.

Descriptive Statistics

Descriptive statistics are presented in Table 1. Friendship quality and romantic relationship quality correlated statistically significant (r = .29, p < .01). Friendship quality correlated significantly with Extraversion (r = .29, p < .01), and Conscientiousness (r = .13, p < .05), and with identity dimensions exploration in depth (r = .22, p < .01) and exploration in breadth (r = .14, p < .05). Romantic relationship quality was not correlated to any of the personality traits. Most correlations between the Big Five traits and identity dimensions were significant and age was negatively correlated with friendship quality (r = −.12, p < .05). Sex differences were tested with a Fisher-Z transformation, but given few significant results, we did not further explore sex differences.

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Table 1.

Descriptive Statistics and Pearson Correlations of the Study Variables.

Variable	M	SD	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
1. Age (W9)	24.84	1.16	—
2. Sex	—	—	−.05	—
3. Education	2.22	0.76	−.02	.12*	—
4. Living situation	—	—	−.25	.18*	.72**	—
5. Extraversion	3.39	0.54	.08	.16**	−.08	−.04	—
6. Agreeableness	3.67	0.39	.07	.12*	−.06	.70	.03	—
7. Conscientiousness	3.51	0.55	−.07	.15**	.12*	.15**	.24**	.25**	—
8. Emotional stability	3.23	0.74	.05	−.31**	−.04	−.08	.44**	.11*	.07	—
9. Openness	3.66	0.46	.05	.03	.08	.12*	.40**	.06	.41**	.27**	—
10. Commitment making	3.58	0.90	.01	.05	−.01	.03	.23**	.12*	.25**	.20**	.18**	—
11. Identification with commitment	3.41	0.76	−.01	.07	−.02	.04	.38**	.07	.31**	.31**	.34**	.71**	—
12. Exploration in depth	3.55	0.68	.09	.11*	.08	.05	.25**	.03	.23**	.07	.26**	.38**	.50**	—
13. Exploration in breadth	3.69	0.68	.10	.11*	−.09	−.06	.21**	.05	.17**	.00	.31**	.31**	.31**	.49**	—
14. Ruminative exploration	2.77	0.89	.05	−.01	.40**	.01	−.28**	−.21**	−.23**	−.36**	−.17**	−.62**	−.56**	−.11*	−.03	—
15. Romantic quality	4.33	0.62	−.04	.15**	.70**	.45**	.13*	.05	.21**	.00	.16**	.10	.09	.04	.07	−.06	—
16. Friendship quality	3.96	0.61	−.11*	.13*	.29**	.79**	.02	.10*	.10*	−.05	.09	.07	.21	.06	−.08	−.01	.42**

Multivariate Mediation Results

To investigate our aims, a multivariate mediation analysis was performed. Results are presented in Table 2 for romantic relationship quality and friendship quality, respectively. The model presented in Figure 1 did not fit the data well (χ2(10) = 113.65, p < .00, CFI = .89, TLI = .22, RMSEA = .17). Modification indices revealed sex was related to Emotional Stability and Extraversion (girls scored higher than boys on Extraversion and lower than boys on Emotional Stability) and educational level was related to Conscientiousness (participants with a higher educational level scored higher on Conscientiousness). Including the paths sex on Extraversion and sex on Emotional Stability resulted in an acceptable model fit (χ2(7) = 12.89, p < .05, CFI = .99, TLI = .93, RMSEA = .05).

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Table 2.

Results of Multivariate Mediation Romantic Relationship Quality and Friendship.

			Romantic Relationship Quality	Friendship Quality	Romantic Relationship Quality			Friendship Quality
Predictors	Mediators	Effect of P on M (path a)	Effect of M on DV (path b)		Direct Effect (path c)	Indirect Effect (path c’)	Total Effect	Direct Effect (path c)	Indirect Effect (path c’)	Total Effect
Educational level	Commitment making	0.03			0.18**			0.03
	Identification with commitment	0.01
	Exploration in depth	0.05
	Exploration in breadth	0.01
	Ruminative exploration	0.70
Extraversion	Commitment making	0.18	−0.03	−0.12	−0.06	−0.01 [−0.05; 0.02]	−0.03	0.21*	−0.02 [−0.07; 0.01]	0.25*
	Identification with commitment	0.24**	0.11	0.01		0.02 [−0.00; 0.08]			0.00 [−0.03; 0.04]
	Exploration in depth	0.21*	0.04	0.18**		0.01 [−0.01; 0.06]			0.04 [0.01; 0.09]
	Exploration in breadth	0.19*	0.04	0.03		0.01 [−0.01; 0.05]			0.01 [−0.01; 0.04]
	Ruminative exploration	−0.15	0.05	−0.03		−0.01 [−0.05; 0.01]			0.00 [−0.01; 0.04]
Agreeableness	Commitment making	0.12	−0.03	−0.12	0.20	−0.01 [−0.06; 0.01]	0.20	−0.06	−0.02 [−0.08; 0.01]	−0.07
	Identification with commitment	−0.03	0.11	0.01		−0.00 [−0.04; 0.02]			0.00 [−0.02; 0.02]
	Exploration in depth	−0.04	0.04	0.18**		−0.00 [−0.3; 0.01]			−0.00 [−0.05; 0.03]
	Exploration in breadth	0.06	0.04	0.03		0.00 [−0.01; 0.05]			0.00 [−0.01; 0.03]
	Ruminative exploration	−0.31**	0.05	−0.03		−0.02 [−0.1; 0.03]			0.01 [−0.03; 0.06]
Conscientiousness	Commitment making	0.29*	−0.03	−0.12	−0.00	−0.01 [−0.08; 0.03]	−0.01	0.04	−0.03 [−0.10; 0.00]	0.04
	Identification with commitment	0.26**	0.11	0.01		0.03 [0.01; 0.10]			0.00 [−0.04; 0.05]
	Exploration in depth	0.15	0.04	0.18**		0.01 [−0.01; 0.05]			0.03 [0.00; 0.08]
	Exploration in breadth	0.03	0.04	0.03		0.01 [−0.01; 0.03]			0.00 [−0.01; 0.02]
	Ruminative exploration	−0.27**	0.05	−0.03		−0.02 [−0.07; 0.02]			0.01 [−0.02; 0.05]
Emotional stability	Commitment making	0.17*	−0.03	−0.12	−0.06	−0.01 [−0.05; 0.02]	−0.06	0.05	−0.02 [−0.06; 0.00]	0.03
	Identification with commitment	0.22**	0.11	0.01		0.02 [−0.01; 0.08]			0.00 [−0.03; 0.04]
	Exploration in depth	−0.03	0.04	0.18**		−0.00 [−0.02; 0.00]			−0.01 [−0.03; 0.02]
	Exploration in breadth	−0.13*	0.04	0.03		−0.01 [−0.04; 0.01]			−0.00 [−0.03; 0.01]
	Ruminative exploration	−0.39**	0.05	−0.03		0.02 [−0.01; 0.08]			0.01 [−0.03; 0.06]
Openness	Commitment making	0.04	−0.03	−0.12	0.00	0.00 [−0.03; 0.01]	0.05	−0.06	−0.00 [−0.05; 0.02]	−0.01
	Identification with commitment	0.22*	0.11	0.01		0.02 [0.01; 0.09]			0.00 [−0.03; 0.05]
	Exploration in depth	0.19*	0.04	0.18**		0.01 [−0.01; 0.06]			0.03 [0.00; 0.09]
	Exploration in breadth	0.40**	0.04	0.03		0.02 [−0.04; 0.09]			0.01 [−0.03; 0.07]
	Ruminative exploration	0.04	0.05	−0.03		0.00 [−0.01; 0.04]			−0.00 [−0.03; 0.01]

Regarding our first aim, no significant direct or indirect effects of personality on romantic relationship quality were found. Results also indicated a direct effect of Extraversion on friendship quality (b = 0.21, p < .05). Concerning our third and fourth aim, results indicated that identity dimensions did not mediate the relationship between personality factors and relationship quality. However, several significant associations were found for personality on identity (path a) and for identity on relationship quality (path b). Extraversion positively predicted three identity dimensions positively: Identification with commitment (b = 0.24, p < .01), exploration in depth (b = 0.21, p < .05), exploration in breadth (b = 0.19, p < .01). Agreeableness negatively predicted ruminative exploration (b = −0.31, p < .01). Conscientiousness positively predicted commitment making (b = 0.29, p < .05), identification with commitment (b = 0.26, p < .001), and negatively predicted ruminative exploration (b = −0.26, p < .001). Emotional Stability significantly predicted commitment making (b = 0.17, p < .05), identification with commitment (b = 0.22, p < .001), exploration in breadth (b = −0.13, p < .05) and ruminative exploration (b = −0.39, p < .001). Openness significantly and positively predicted identification with commitment making (b = 0.22, p < .02), exploration in depth (b = 0.19, p < .05) and exploration in breadth (b = 0.40, p < .001). A significant effect of exploration in depth (b = 0.18, p < .01) on friendship quality was found. Identity dimensions were not significantly associated with romantic relationship quality. Further, a significant effect of educational level on romantic relationship quality (b = 0.18, p < .01) was found indicating that participants with higher educational levels reported a higher romantic relationship quality.

The Association Between Personality and Relationship Quality

Consistent with previous findings on friendship quality (Festa et al., 2012; Wilson et al., 2015), people high on Extraversion reported a higher friendship quality 3 years later than people low on Extraversion. Young adults scoring high on Extraversion are more outgoing and experience more positive affect. Consequently, they have more opportunities to get to know people and are more likely to become friends with people than individuals low on Extraversion (Selfhout et al., 2010). As expected, Extraversion is more relevant in friendships than in romantic relationships. The positive affect and sociable character of individuals high on Extraversion that result in outgoing and social behavior may be more beneficial for friendships than for romantic relationships (Schaffhuser et al., 2014; Wilson et al., 2015).

Further, we did not find empirical evidence for our hypotheses. One possible explanation may be that previous research on romantic relationships concentrated on marital satisfaction of adults between 35 and 59 years (Malouff et al., 2010; O’Meara & South, 2019). In contrast, our study focused on emerging adults between 21 and 27 years. Emerging adulthood is, next to other features, characterized by instability in relationships, self-focus with few obligations, identity explorations and diverse trajectories in education, work and social life (Arnett et al., 2014). With regard to Emotional Stability, Watson and colleagues (2000) reported that people high on Neuroticism experience lower relationship quality over 18 years of marriage. This negative effect of Neuroticism may not be that pronounced in the early years of relationships. A potential variable influencing the association between personality and relationship quality is the partner´s personality or, even more influential, congruence between partners personalities, which correlates with relationship satisfaction (Gonzaga et al., 2007). There is evidence that congruence between self-rated personality and perception of the partners personality predicts satisfaction (Zentner, 2005). Finally, where most work is based on cross-sectional designs, this study is longitudinal, covering a time span of 3 years. Future research should focus on long-term effect of personality on relationship quality in emerging adults.

Do Identity Dimensions Mediate Relations Between Personality and Relationship Quality?

Our results indicate that the longitudinal associations between personality factors and relationship quality are not mediated by identity dimensions. An explanation may be that we did not assess identity processes with respect to friendship and romantic relationships, but rather with respect to the more generic domain of future choices. Whereas identity processes refer to how identity is formed, identity content expresses what part of identity is formed (Vosylis et al., 2018). Regarding identity content, research shows that the overlap between global and domain specific identity is only modest (Piotrowski, 2022), so a global identity measurement like the DIDS may only partly explain domain specific outcomes such as relationship quality. Vosylis and colleagues (2018) hypothesize that looking at a global identity process may suggest there is no effect whereas an effect may be present on a domain specific level.

Strength and Limitations

The longitudinal design of this study offered the opportunity to investigate the relationship between concepts over a longer period in a large and heterogeneous sample. By including all Big Five domains and all identity dimensions in a multivariate model, we could empirically test the impact of each concept on two different kinds of relationships. Considering the overlapping yet unique features of friendships and romantic relationships (Barry et al., 2009; Wilson et al., 2015), the current study adds to the understanding of both types of relationships, allowing to compare associations among personality and identity and creating context-specific models of relationships (Barry et al., 2009; Wilson et al., 2015).

However, this study is not without limitations. A first limitation is that we relied on self-reported measures, which may give subjective and biased information (Schaffhuser et al., 2014). Whereas the self-perception provides a unique inside view on oneself, the perceptions of intimate partners or friends offers an outside perspective that can be more objective and less biased (Schaffhuser et al., 2014).

Further, identity was measured with the Dimensions of Identity Development Scale (DIDS; Luyckx, et al., 2008). This questionnaire measures identity dimensions with respect to future life choices instead of specific identity domains. As hypothesized by Vosylis and colleagues (2018) focusing on a global identity process may suggest there is no effect whereas an effect may be present on a domain specific level. The fact, that we found some significant links with a global concept of identity anyways, shows that there is much potential in the investigation of emerging adults’ identities and relationships. As the present study was conducted within the Flemish Study on Parenting, Personality and Development (FSPPD; Prinzie et al., 2003) not every concept was measured in each wave. Therefore, we could not control for stability of relationship satisfaction and a full longitudinal design allowing for cross-lagged associations and directionality of effects was not possible. In line with this, the present study cannot add to the discussion about the ordering of identity and intimacy as proposed by Erikson (1982) and as discussed in several studies (Bosch & Curran, 2011; Montgomery, 2005). In addition, there is some heterogeneity of identity within the individual (Lichtwarck-Aschoff et al., 2008; Schwartz et al., 2011). Specifically, identity processes on a macro-level (months and years) and a micro-level (days) may operate differently and should be investigated separately from each other. Whereas day-to-day changes may be rapid and reactive, long-term changes may involve slower and more agentic decision making. Future research should give more attention to the topic with longitudinal designs using domain-specific instruments and short-term identity processes to make the effects more pronounced and discover developmental trajectories. Further, future research should investigate the developmental ordering of identity and intimacy in today’s emerging adults and investigate potential underlying developmental processes such as adopting adult roles and achieving adulthood criteria (marriage, job, living situation) that may interact with both intimacy and identity development.

Second, our study was restricted to a Flemish sample of emerging adults. Given the universal importance of identity and interpersonal relationships over various cultures, both individualistic and collectivistic (Becker et al., 2012), our results are still instructive about identity and relationships in emerging adults. Nevertheless, it should be noted that culture has been found to moderate the associations of personality traits with well-being (Klimstra et al., 2012; McAdams, 2015). Hence, each culture´s own characteristic may have unique effects on each of our study variables and future research should assess these associations in other cultures, especially collectivistic cultures, as well.

Further, we assessed a population-based sample, so our results should not be extended to clinical populations. For example, among clinical populations, identity development may impact relationships differently than in non-clinical samples. Indeed, research reported that clinical samples show higher identity distress in adolescents than non-clinical samples (Wiley & Berman, 2013). Individuals with more identity distress also showed more psychological adjustment problems and psychopathology, which may also present as relationship problems. Therefore, future research should investigate associations between identity and relationship quality in clinical samples.

Our results have some implications for applied science. Emerging adulthood needs to be considered as an important and unique period in life, characterized by both opportunities and risks for mental health (Arnett et al., 2014). The task of establishing intimacy is considered a critical life span turning point, where key experiences affect trajectories of young individuals in either positive or compromising ways (Montgomery, 2005). In line with this, our results show that it is important to increase awareness about individuals low on Extraversion, Agreeableness, Conscientiousness and Emotional Stability that are at risk of falling into ruminative explorations and may get stuck by the countless opportunities and may not be able to commit to one option (Klimstra et al., 2013).

Conclusion

In sum, we found that emerging adults high on Extraversion report a higher friendship quality 3 years later. We did not find empirical evidence that identity dimensions mediate the link between personality and romantic relationship or friendship quality. Furthermore, we supported the notion that all personality domains are associated with identity dimensions in emerging adults and showed that exploration in depth is beneficial for friendship quality.