1. Introduction
In recent decades, alongside the expansion of marital therapy, various theories have been developed to explain family functioning. Clinical instruments have also been created to identify strengths, strategies, requirements, and changes within the family system. This reciprocal interaction between research and clinical practice has been fundamental to the development and refinement of family and marital therapy.
A key feature of such theoretical models and instruments is their ability to differentiate families that require therapy. The Circumplex Model (Olson et al., 1985) has been proven effective in distinguishing non-clinical cases (Drumm, Carr, & Fitzgerald, 2000), allowing interventions to be planned with a focus on the dimensions of greatest stress within the family system.
The Circumplex Model posits that family functioning can be defined along two dimensions—cohesion and adaptability—where communication plays a facilitating role. High cohesion and adaptability reflect balanced family systems, whereas low values indicate dysfunctional systems. The model is dynamic, viewing change as beneficial for maintaining and improving family functioning. Alterations in cohesion and adaptability are key factors in coping with stress and the changes inherent in the family life cycle (Olson & Gorall, 2003). In stressful situations, balanced systems tend to adapt, while dysfunctional systems remain rigid, thereby exacerbating stress (Olson, 2000).
Cohesion can be defined as a support factor. According to Olson (2000: p. 145, our translation), it is the “emotional bonding that couples and family members have with each other”. This dimension assesses the proximity-distance axis in relationships between family members, classified into four levels: Disengaged (very low cohesion), Separated (low to moderate cohesion), Connected (moderate to high cohesion), and Enmeshed (very high cohesion). Extreme levels are considered dysfunctional, particularly in long-term relationships, whereas central levels are deemed most advantageous.
Marital dissatisfaction is associated with lower family cohesion (Henderson, Sayger, & Horne, 2003), which can lead to psychological problems in both childhood and adulthood (Henderson et al., 2003; Shek, 2002). Moderate cohesion allows couples and families to balance separation and proximity according to situational demands, making it more functional (Olson, 2000; Olson & Gorall, 2003).
Adaptability is a structural factor defined as “the amount of change in leadership, roles, and relationship rules” (Olson & Gorall, 2003: p. 519, our translation). It ranges on a continuum of four categories: Rigid (very low capacity for change), Structured (low to moderate capacity for change), Flexible (moderate to high capacity for change), and Chaotic (very high capacity for change). Extreme levels correlate with poor family functioning, whereas central levels indicate optimal functioning. Change and stability are both essential in family dynamics, although many families maintain a rigid structure over time (Olson, 2000).
Communication facilitates changes in both cohesion and adaptability across various life situations (Olson & Gorall, 2003). Balanced families display more positive communication, which helps maintain that balance. Poor communication prevents beneficial changes in marital functioning, keeping families at extreme levels (Olson, 2000).
Cohesion, Adaptability, and Communication: Impact on the Couple and Family
Major changes in family systems often occur during crises. Kouneski (2000) notes that even in accidental crises, cohesion and particularly adaptability play a crucial role in family and marital functioning. Rigid systems have fewer coping strategies and tend to become even more rigid under stress. Improving communication can promote systemic changes.
Balanced families display greater flexibility and oscillation between dimensions according to situational needs, achieving appropriate functioning while experiencing both independence and closeness. Although typically positioned within central dimensions, these families may exhibit extreme behaviours if the situation demands (Barnes & Olson, 1985; Olson & Gorall, 2003).
Balanced families also exhibit more effective communication strategies, including support, positive affect, and information sharing (Rodick, Henggler, & Hanson, 1986). Extreme patterns may be functional in specific situations but are generally harmful if they become fixed, though they can be adaptive for some families, including those from particular ethnic groups (Olson, 2000).
Family and Marital Satisfaction, Life Cycle, and Gender
Analysis of family structure requires examining the characteristics, roles, and relationships of all members, as well as the stages of the family life cycle (Gómez-Clavelina et al., 1999). Satisfaction with the family bond can be defined as “the extent to which the need for cohesion and closeness in family relationships is met” (Vandeleur, Jeanpretre, Perez, & Schoebi, 2009: p. 1206, our translation).
Cohesion and adaptability, despite their importance, function differently in long-term relationships (Kouneski, 2000). High cohesion helps couples during periods of difficult adjustment, whereas happy and satisfied couples exhibit balanced adaptability (James & Hunsley, 1995). Relationships are typically perceived as more cohesive by women, likely because they seek closer relational bonds.
Couples from higher socioeconomic classes report more variable relationships (Noller & Shum, 1990). Relationship versatility is particularly notable in unions under five years, where adaptability is more flexible, likely due to adjustments in the early years or rigidity that develops with longer marriages (Noller & Shum, 1990). However, studies on adaptability across the life cycle show inconsistencies. Some suggest that long-term couples report higher satisfaction. Recent and long-term couples show similar cohesion levels, though older couples demonstrate greater adaptability (Mathis & Tanner, 1991).
A review of the literature on cohesion and adaptability reveals clear trends and similarities. The need to adjust cohesion and adaptability across relationship stages is particularly evident during crises (Olson, 2000; Peleg-Popko & Dar, 2001; Olson & Gorall, 2003). Couples and families at extreme levels are more dysfunctional compared with balanced families, which demonstrate more positive communication patterns and greater satisfaction, thereby helping to maintain harmony (Carvalho, Freitas, Leuschner, & Olson, 2014; Olson et al., 1985; Olson, 2000; Olson & Gorall, 2003). Gender differences are also observed in perceived and desired cohesion and adaptability (Baiocco, Cacioppo, Laaghi, & Tafà, 2013).
In addition, contemporary demographic changes have led to an increasing number of adult children remaining in the parental home well into adulthood. This situation can reshape family dynamics and impose unique challenges on marital functioning. Recognising this, our study considers “Couples with Adult Children at Home” as a distinct group within the marital life cycle, as prolonged co-residence may affect both cohesion and adaptability in ways not captured by traditional classifications (Umberson et al., 2005).
Recent research continues to emphasise the dynamic nature of marital adaptability and its association with relational satisfaction (Fu et al., 2024). These studies show that adaptability remains a strong predictor of long-term relationship maintenance. Including such findings supports the ongoing relevance of the Circumplex Model in understanding modern family systems.
1.1. Objective
This study aims to achieve a better understanding of marital relationships over time, examining processes of marital cohesion and adaptability while considering both the life cycle and gender. It also seeks to clarify aspects of the literature that remain unclear and to address limitations of previous studies’ samples and potential biases, such as the idealisation of the early years of marriage when assessed retrospectively.
1.2. Research Design
This is an exploratory, cross-sectional, and comparative study across different stages of the couple’s life cycle and between genders, designed to address the following questions:
How do marital cohesion and adaptability vary between men and women?
What are the differences and similarities between genders?
How do cohesion and adaptability vary across the life cycle for men and women?
What are the differences and similarities between spouses in real and ideal cohesion and adaptability across the different stages of marriage?
Are there differences in cohesion and adaptability between married couples and cohabiting couples?
2. Method
2.1. Participants
The study intentionally focused on couples reporting high marital satisfaction. This was a deliberate methodological decision, as understanding well-functioning marital systems offers valuable insights into adaptive processes and relational balance across the marital life cycle. Marital satisfaction was assessed using a single composite index specifically designed to identify couples within the satisfied range, with 89.2% of women and 93.5% of men between satisfy and very satisfy, without significative differences between genders (p = 0.04). This approach allowed us to examine the dynamics of cohesion and adaptability in stable, non-clinical relationships, with the goal of later applying this knowledge to therapeutic work with couples showing lower satisfaction. Preliminary analysis of FACES-III scores confirmed that most participants were within the balanced range for Cohesion and Adaptability, consistent with non-clinical samples described in previous research (Olson & Gorall, 2003; Carvalho et al., 2014).
The study included 370 participants (185 couples). Group classification followed classic literature on the family life cycle (Carter & McGoldrick, 1989; Neighbourgh, 1985; Relvas, 2004). However, our sample included a substantial number of couples whose adult children still lived at home; therefore, we considered them a distinct group, supported by literature indicating this situation as a potential vulnerability for the couple’s relationship (Umberson, Williams, Powers, Chen, & Campbell, 2005).
Accordingly, the groups were defined as follows:
Couple Formation: Couples married or cohabiting for less than four years (inclusive), with no children from the current or previous relationship living at home. Couples married less than four years with children were excluded.
Couples with Young Children: Couples with children up to five years old from the current relationship, regardless of years of marriage or cohabitation. Couples with children from previous unions were excluded to focus on the impact of the birth of children from both partners.
Couples with School-Aged Children: Couples with children aged six to twelve years (inclusive), regardless of years of marriage or cohabitation. Couples with additional older children from the current or previous unions were excluded.
Couples with Adolescent Children: Couples whose children are aged thirteen to nineteen years. Couples with older children from current or previous unions were excluded.
Couples Whose Children Have Left Home: Couples whose children left home less than four years ago (inclusive). Couples with other children still living at home were excluded.
Couples with Adult Children at Home: Couples with adult children (over twenty-three years old) still living at home. Couples with children aged twenty to twenty-three (university-aged, considered neither adults nor adolescents) were excluded.
Elderly Couples: Couples without children at home in which at least one partner is aged sixty or above. All such couples were included, regardless of the number of marriages or children from previous unions.
Sample description can be seen in Table 1 and Table 2.
Table 1. Sample description.
|
|
N |
% |
Life cycle stage |
Couples Formation |
30 |
16.2 |
Couples with small children |
40 |
21.6 |
Couples with school age children |
26 |
14.1 |
Couples with adolescent children |
38 |
20.5 |
Couples whose children have left home |
8 |
4.3 |
Elderly couples |
18 |
9.7 |
Couples with adult children at home |
25 |
13.5 |
Total |
185 |
100.0 |
Union |
Mariage |
138 |
74.6 |
Cohabitation |
47 |
25.4 |
Total |
185 |
100.0 |
Marriage length |
<1 year |
1 |
0.7 |
1 - 5 years |
12 |
8.7 |
6 - 10 years |
26 |
18.8 |
11 - 15 years |
14 |
10.1 |
16 - 20 years |
21 |
15.2 |
>20 years |
64 |
46.4 |
Total |
138 |
100.0 |
Cohabitation length |
<1 year |
2 |
4.3 |
1 - 5 years |
26 |
55.3 |
6 - 10 years |
8 |
17.0 |
11 - 15 years |
6 |
12.8 |
16 - 20 years |
2 |
4.3 |
>20 years |
3 |
6.4 |
Total |
47 |
100.0 |
Existence of children |
Yes |
150 |
81.1 |
No |
35 |
18.9 |
Total |
185 |
100.0 |
|
1 child |
60 |
40.0 |
2 children |
73 |
48.7 |
3 children |
14 |
9.3 |
> 3 children |
3 |
2.1 |
Total |
185 |
100.0 |
Table 2. Sample description (continuation).
|
|
Female |
Male |
N |
% |
N |
% |
Age |
<30 years |
32 |
17.3 |
18 |
9.7 |
30 - 39 years |
55 |
29.7 |
60 |
32.4 |
40 - 49 years |
49 |
26.5 |
43 |
23.2 |
50 - 59 years |
44 |
23.8 |
59 |
31.9 |
60 - 69 years |
4 |
2.2 |
4 |
2.2 |
70 - 79 years |
1 |
0.5 |
1 |
0.5 |
Total |
185 |
100.0 |
185 |
100.0 |
|
Min. = 20 |
Max. =80 |
Min. = 19 |
Max. = 82 |
|
Mean = 41.87 |
Standard Deviation
= 12.70 |
Mean = 44.50 |
Standard Deviation
= 2.69 |
Occupation |
Retirement |
18 |
9.7 |
22 |
11.9 |
Unemployee |
4 |
2.2 |
6 |
3.2 |
Housewifely |
8 |
4.3 |
0 |
0.0 |
Student |
3 |
1.6 |
1 |
0.5 |
Self-employee |
11 |
5.9 |
30 |
16.2 |
Salaried employee |
128 |
69.2 |
115 |
62.2 |
Salaried employee and self employed |
4 |
2.2 |
4 |
2.2 |
Working student |
1 |
0.5 |
4 |
2.2 |
No answer |
8 |
4.3 |
3 |
1.6 |
Total |
185 |
100.0 |
185 |
100 |
Education |
Primary Education |
13 |
7.0 |
8 |
4.3 |
Basic Education |
8 |
4.3 |
13 |
7.0 |
Unified Secondary Education |
24 |
13.0 |
34 |
18.4 |
Complementary Secondary Education |
50 |
27.0 |
49 |
26.5 |
High School |
12 |
6.5 |
5 |
2.7 |
Bachelor’s Degree |
5 |
2.7 |
16 |
8.6 |
Licenciate Degree |
60 |
32.4 |
52 |
28.1 |
Master’s Degree |
12 |
6.5 |
6 |
3.2 |
Doctorate |
0 |
0.0 |
1 |
0.5 |
No answer |
1 |
0.5 |
1 |
0.5 |
Primary Education |
13 |
7.0 |
8 |
4.3 |
Total |
185 |
100.0 |
185 |
100 |
2.2. Materials
Although communication is a core facilitating dimension of the Circumplex Model, it was not directly assessed in this study. The FACES-III version used here measures only the dimensions of Cohesion and Adaptability. Communication was conceptually considered but excluded from the empirical analysis to maintain focus on structural and relational aspects.
2.3. Procedure
Questionnaires were collected over 18 months in various services across the Lisbon metropolitan area. This was a convenience sample obtained using a snowball recruitment method. The initial sample included 596 valid questionnaires (298 couples). Only 185 couples (138 married and 47 cohabiting) met the inclusion criteria for participation.
The study was approved by the ISPA Ethics Committee, and all participants provided informed consent.
3. Results
The analysis of differences in cohesion and adaptability between men and women, using the paired-sample t-test, revealed significant differences for p ≤ 0.001 in ideal adaptability, with mean values higher for females (40.17) compared with males (38.17), although with a small effect size (Cohen’s d = 0.39). No significant differences were found for real adaptability.
Regarding cohesion, differences approached significance for both real (p = 0.097) and ideal (p = 0.090) values, with women again showing higher means.
Significant differences were found in both genders for p ≤ 0.001 between perceptions of real and ideal relationships, in terms of both cohesion and adaptability. However, the effect size for cohesion was moderate, whereas it was large for adaptability.
The analysis of discrepancies between partners’ perceptions of ideal and real values revealed no significant differences for cohesion. Adaptability, however, showed significant gender differences, with higher discrepancy values among women, although the effect size was small.
Our second research question aimed to study the variation in cohesion and adaptability across different relationship stages by gender. For females, a one-way ANOVA revealed significant differences between stages in the perception of ideal cohesion. Post hoc LSD (Least Significant Difference) tests showed that women without children (Couple Formation) differed from women with school-aged children (p = 0.008), women in old age (p = 0.001), and women with adult children living at home (p = 0.029). Thus, the absence of children corresponded to higher ideal cohesion values. Differences were also found between women in old age and women with adolescent children (p = 0.021) and women with young children (p = 0.007), with older women exhibiting lower ideal cohesion.
For males, one-way ANOVA revealed significant differences between stages in male ideal adaptability. Using the LSD test, men with adult children living at home showed significant differences compared with men without children (p = 0.000), men with young children (p = 0.001), men with school-aged children (p = 0.002*), and men with adolescent children (p = 0.033). Men whose adult children still lived at home had lower ideal adaptability than the aforementioned groups.
Analysis of discrepancies between real and ideal values across all relationship stages did not reveal significant differences for cohesion or adaptability, either among men or women.
To better understand the results, partners were compared within each relationship stage. Significant differences between partners were found for ideal adaptability in: couples with young children [t(39) = 1.979, p = 0.055, Cohen’s d = 0.48], couples with adolescent children [t(37) = 2.842, p = 0.007, Cohen’s d = 0.66], couples whose children have left home [t(7) = 1.920, p = 0.096, Cohen’s d = 1.00], and couples with adult children still living at home [t(25) = 3.043, p = 0.006, Cohen’s d = 0.86]. In all these cases, women reported higher ideal adaptability values.
Comparing real-ideal discrepancies in cohesion and adaptability between genders within each group, significant differences were found for adaptability in couples with adult children living at home, where women showed higher values (7.55) than their spouses (2.44), with a moderate-to-high effect size (Cohen’s d = 0.73).
Although not statistically significant, other results are noteworthy due to approaching significance and/or nearly moderate effect sizes. In couples in formation, the real-ideal discrepancy in cohesion was higher for men (3.10) than for women (2.27) (p = 0.088, Cohen’s d = −0.47). In couples with young children, the female real-ideal discrepancy in adaptability (8.21) was higher than for males (5.80) (p = 0.058, Cohen’s d = 0.44). In couples whose children have left home, women showed higher real-ideal discrepancies in both cohesion (F: 7.01, M: 3.45, p = 0.408, Cohen’s d = 0.45) and adaptability (F: 8.08, M: 5.38, p = 0.377, Cohen’s d = 0.47). In older couples, the real-ideal discrepancy in cohesion was higher for men (F: 0.76, M: 2.13, p = 0.251, Cohen’s d = −0.46).
Finally, differences in cohesion and adaptability between married couples and cohabiting couples were examined. Results showed higher cohesion and adaptability values for men in cohabiting relationships compared with married men, with effect sizes (Cohen’s d) ranging from 0.36 to 0.55.
For females, differences were only found in real and ideal cohesion, with women in cohabiting relationships showing higher values in both (Real Cohesion: Cohen’s d = 0.34; Ideal Cohesion: Cohen’s d = 0.49).
Higher values were found for the ideal scales (cohesion and adaptability) in both types of relationship. However, the largest discrepancy was observed in the adaptability scale (Cohen’s d between −0.98 and −1.45).
4. Discussion
How Marital Cohesion and Adaptability Vary between Men and Women
The comparison between real and ideal values of cohesion and adaptability for both men and women revealed significant differences for both dimensions. Both men and women idealise relationships with higher cohesion and adaptability, with the difference being greater for adaptability.
Gender Differences and Similarities
The comparison between the male and female samples shows that men and women exhibit similar patterns of cohesion and adaptability. Statistically significant differences between genders were only found for ideal adaptability, which was higher among women. These findings are supported by the analysis of discrepancies. The results suggest that women desire greater flexibility and change in aspects related to leadership, control, discipline, roles, and rules.
How Marital Cohesion and Adaptability Vary across the Life Cycle for Men and Women
Analysis within each gender regarding changes in cohesion and adaptability over the life course showed that, for women differences were only found in ideal cohesion. During the Couple Formation stage, women reported higher ideal cohesion than other groups in the female sample. This may reflect the idealisation characteristic of this life stage, when the couple begin their relationship and project their future, or the need at this stage to create a consistent and cohesive marital system capable of facing the challenges of early life together. Conversely, the lowest values of ideal cohesion were reported by women in older couples. These values may result from a shared and established trajectory that achieved an adequate level of cohesion and allowed the couple to navigate various marital crises.
For men, differences were only observed in ideal adaptability, with the lowest values recorded among men with adult children living at home. According to Umberson et al. (2005), adult children at home can negatively impact the parents’ relationship, as couples may spend less quality time together.
Differences and Similarities between Spouses in Real and Ideal Cohesion and Adaptability across Marital Stages
Comparisons within each marital stage revealed gender differences in certain stages of marital life, but only for ideal adaptability. Adaptability is defined by Olson and Gorall (2003) as “the amount of change in leadership, roles, and relationship rules” (p. 19, our translation). These results, reflecting a desire for greater adaptability—particularly among women with children—suggest that roles within couples today may still resemble those in traditional marriages, where child-related responsibilities largely fall on women.
These stages correspond to the birth of the first child, adolescence, and the empty-nest period. The significant changes in family dynamics introduced by children, which evolve as children grow, may increase women’s responsibilities and consequently accentuate gender role disparities within the relationship (Belsky, Lang, & Huston, 1986), potentially driving the idealisation of relationships with greater adaptability.
Furthermore, this idealisation is also expressed by women with adult children living at home, where roles and relationship rules within the family triad can be challenging. It is only at this stage that differences in ideal-real adaptability discrepancies are observed, with women again showing significantly higher values.
Except for stages with school-aged and adolescent children, all other stages showed values at the threshold of significance or with nearly moderate effect sizes in at least one variable (cohesion or adaptability). These findings suggest smaller differences between real and ideal values in at least one member of the couple.
Differences in Cohesion and Adaptability between Married and Cohabiting Couples
Both types of union revealed similar discrepancies between real and ideal values for the dimensions studied.
Men and women perceive cohesion and adaptability in their real relationships similarly.
When idealising relationships, women—more than men—desire greater adaptability in romantic relationships.
Comparing real and ideal relationships reveals differences in both dimensions, but greater for adaptability in both genders.
These real-ideal discrepancies in adaptability are more pronounced among women.
Comparing women across the life course, differences were only found in ideal cohesion. During Couple Formation, women reported higher ideal cohesion than at stages with school-aged children, adult children at home, or in old age. Women in the Old Age Group showed lower ideal cohesion than women with young or adolescent children.
Comparing men across the life cycle, differences were only found in ideal adaptability, which was lower when adult children lived at home compared to stages with couple formation, young children, school-aged children, or adolescents.
Evaluating marital stages and comparing women with men at each stage, women idealised higher adaptability than men during stages with young children, adolescents, adult children at home, or empty-nest periods. Women with adult children living at home also showed greater discrepancies between real and ideal adaptability compared with their spouses.
From a clinical perspective, these findings highlight the importance of monitoring perceived and ideal levels of adaptability throughout the marital life cycle. Therapists working with couples can use this information to design interventions that target flexibility in roles, leadership, and decision-making—particularly during transition periods such as the arrival of children or the empty-nest phase. Recognizing gender differences in the desire for adaptability may also help professionals sup port more balanced negotiation processes between partners.
Both partners in cohabiting relationships showed higher cohesion, and men showed higher adaptability than married men.
In our sample, composed of couples with high marital satisfaction, no major differences were observed in the variables studied. Nonetheless, adaptability appears to merit greater attention in couple assessment, as it consistently shows the largest differences across various comparisons and correlations. Women desire greater adaptability, and it varies across stages of the marital life cycle and between genders.
Although our study addresses, or at least clarifies, some initial questions, it primarily raises a set of questions for future investigation. For example, it is necessary to clarify the effect of adult children living at home, where differences in cohesion and adaptability values and their discrepancies are observed, particularly in comparison with other life stages.
It would also be valuable—considering the intended general therapeutic utility of this research—to compare current findings with a clinical population. In this context, reproducing the study with couples at different stages of therapy would be relevant, evaluating the effectiveness of interventions in altering the strengths and structure of marital relationships throughout the therapeutic process.
5. Limitations
Although the present study provides valuable insights into marital cohesion and adaptability across the life cycle, several limitations should be acknowledged. First, the cross-sectional design prevents causal inferences about changes over time. Future longitudinal research could clarify how cohesion and adaptability evolve within the same couples across different life stages. Second, data were collected through self-report questionnaires, which may be affected by social desirability and shared method variance. Third, the convenience and snowball sampling methods may limit the generalisability of the findings beyond the metropolitan area of Lisbon and to couples with lower educational or socioeconomic levels.
Although the study focused on couples with high marital satisfaction, this should not be viewed as a limitation but rather as a specific research scope. The intention was to understand how cohesion and adaptability operate in well-functioning marital systems, identifying the structural and relational patterns that sustain satisfaction over time. These findings provide a baseline for comparison with future studies involving clinical or distressed couples, potentially guiding therapeutic interventions aimed at restoring balance in cohesion and adaptability.
Future studies including clinical or less satisfied couples could enhance understanding of how cohesion and adaptability function under greater relational strain.
6. Conclusion
This study examined gender and life-cycle variations in marital cohesion and adaptability among Portuguese couples who reported high levels of marital satisfaction. The sample was intentionally composed of satisfied couples, with the purpose of identifying the adaptive mechanisms that characterise well-functioning relationships. Both men and women perceived similar levels of cohesion and adaptability in their real relationships, yet women consistently idealised greater adaptability.
Differences were most evident at transitional life stages, such as the formation of the couple and the period in which adult children remain at home.
The finding that cohabiting partners demonstrated higher cohesion and adaptability than married partners may reflect cultural and generational specificities within the Portuguese context, where cohabitation increasingly represents a deliberate and egalitarian choice. Since the late twentieth century, it has become common in Portugal for couples to cohabit before marriage, and many choose not to marry at all.
This social shift may have contributed to more flexible relational dynamics and more negotiated roles within cohabiting unions, which in turn align with higher levels of cohesion and adaptability.
By focusing on well-adjusted couples, this study contributes to a clearer understanding of the structural and relational factors that sustain marital satisfaction. These insights may serve as a reference framework for clinical work with distressed couples, particularly in promoting flexibility, balanced leadership, and adaptive negotiation of roles. Future research should extend this analysis to clinical populations and explore contextual factors such as socioeconomic change, gender roles, and intergenerational co-residence.