Justin Michel

Hamza Sibai

Gil Kim

Rebecca Adams

Hyunjin Victoria Ingram

Richard Seung

Nathan Macalpine

Dolly Mehta

Mahua Das

Ayesha Sikdar

Kevin Philip Lee

Phyllis Mobbs

Amrita Chopra

Kelly Le

Amina Yousaf

Alyssa Di

Keywords: Intercultural couples, identity integration, marginalization, relationship quality

Despite the growing prevalence of intercultural romantic relationships-in which partners identify with different racial, national or religious backgrounds-people in intercultural relationships still face marginalization and disapproval from others.

Relationship marginalization sends a message to couples that they do not belong together, and partners may feel that their cultural identity and their relationship are disconnected.

Two studies -one study of people in intercultural relationships and one of both members of intercultural couples-showed that when people perceived greater relationship marginalization, they were more likely to separate their couple identity from their cultural identity or believe they had to choose between these identities, and they were less likely to integrate these identities. Less integration and more separation between a person's couple and cultural identities was associated with lower relationship quality for both partners. The findings suggest that marginalization can create challenges for the maintenance and quality of intercultural relationships.

Richard N. Lalonde is a Professor at York University. His research is at the intersection of culture and intergroup relations, with a focus on issues such as acculturation, bicultural identity and discrimination.

Intercultural relationships -relationships in which partners identify with different cultures or ethnicities [START_REF] Livingston | Intermarriage in the US 50 years after Loving v. Virginia[END_REF]-are integral to human history by virtue of migration and intergroup contact [START_REF] Kramsch | Intercultural contact, hybridity, and third space[END_REF]. These relationships have been steadily increasing in Canada (4.6%;Statistics Canada, 2011) and the United States (10.2%; [START_REF] Rico | Growth in Interracial and Interethnic Married-Couple Households[END_REF]. Despite the growing prevalence and visibility of intercultural relationships, prejudice and discrimination against intercultural couples continues [START_REF] Valentine | Conceptions of mixed race and the politics of temporality[END_REF], with people demonstrating explicit and implicit bias [START_REF] Skinner | A robust bias against interracial couples among White and Black respondents, relative to multiracial respondents[END_REF], and even disgust [START_REF] Skinner | Yuck, you disgust me!" Affective bias against interracial couples[END_REF], towards intercultural relationships. Marginalization of intercultural couples sends a message to partners in these couples that they do not belong together, and may suggest that their couple identity (e.g., "lover," "partner," or "spouse") and their cultural identity (e.g., Korean-American) are irreconcilable and cannot be integrated. This fragmented identity experience may play a role in the quality of the romantic relationship. The current research is the first to investigate whether perceived marginalization is associated with how people in intercultural relationships negotiate their couple and cultural identities as well as how a person's identity negotiation is associated with both partners' relationship quality.

Marginalization of Intercultural Relationships

Relationship marginalization involves actual or perceived social disapproval of a relationship from family, friends, and society [START_REF] Lehmiller | Marginalized relationships: The impact of social disapproval on romantic relationship commitment[END_REF]. Despite their growing presence, intercultural couples are still a minority who are stigmatized for violating the strong cultural norm of endogamy (e.g., [START_REF] Gaines | Relationship maintenance in intercultural couples: An interdependence analysis[END_REF][START_REF] Gaines | Interethnic marriage in the United States: An introduction[END_REF][START_REF] Moran | Love with a proper stranger: What anti-miscegenation laws can tell us about the meaning of race, sex, and marriage[END_REF]. Norm violation tends to be met with social disapproval [START_REF] Bell | Exploring parental approval and disapproval for Black and White interracial couples[END_REF][START_REF] Lehmiller | Marginalized relationships: The impact of social disapproval on romantic relationship commitment[END_REF] as well as prejudice and discrimination [START_REF] Killian | Interracial Couples, Intimacy, and Therapy: Crossing Racial Borders[END_REF][START_REF] Lewandowski | Perceptions of interracial couples: Prejudice at the dyadic level[END_REF]. The marginalization of intercultural couples has a long history. Racial hierarchies embedded in colonization and slavery constructed Whites as superior and non-Whites as inferior, thereby justifying the subordination, exploitation and enslavement of racialized minorities (Hall, 1995). Current marginalization of intercultural relationships is rooted in these essentialist beliefs that racial separation is the natural order of social organization, including mate selection [START_REF] Killian | Interracial Couples, Intimacy, and Therapy: Crossing Racial Borders[END_REF]. In the first half of the 20 th century in America, intercultural relationships were marginalized through institutional measures such as laws that made such unions illegal and subject to persecution [START_REF] Fang | Romance across the social status continuum: Interracial marriage and the ideological asymmetry effect[END_REF]. It was not until 1967 that the Loving v. Virginia case won interracial couples the right to marry [START_REF] Wardle | Loving v. Virginia and the Constitutional right to marry, 1970-1990[END_REF].

Social shifts like the civil rights movement and the legalization of interracial relationships have yielded more favorable explicit attitudes towards these couples [START_REF] Killian | Interracial Couples, Intimacy, and Therapy: Crossing Racial Borders[END_REF][START_REF] Uskul | The role of culture in intergenerational value discrepancies regarding intergroup dating[END_REF]. However, intercultural couples may still face disapproval and marginalization from society and close others. Recent experimental studies find that monocultural Americans express explicit and implicit bias against interracial couples [START_REF] Skinner | A robust bias against interracial couples among White and Black respondents, relative to multiracial respondents[END_REF], and implicitly react with disgust towards interracial couples, which in turn leads to implicit dehumanization [START_REF] Skinner | Yuck, you disgust me!" Affective bias against interracial couples[END_REF].

Marginalization experiences can heavily impact relationship quality and longevity. Support for a relationship from one's social network has been shown to predict greater relationship well-being [START_REF] Blair | Perceived social network support and well-being in samesex versus mixed-sex romantic relationships[END_REF] and quality [START_REF] Sprecher | The influence of parents and friends on the quality and stability of romantic relationships: A three-wave longitudinal investigation[END_REF]. Disapproval of interracial, same-sex or age-gap relationships by society and close others has been associated with lower relationship investment [START_REF] Lehmiller | Marginalized relationships: The impact of social disapproval on romantic relationship commitment[END_REF]. In another study of Black and White interracial couples, parental disapproval of the relationship was associated with discomfort, awkwardness, and anxiety for both partners in the relationship [START_REF] Bell | Exploring parental approval and disapproval for Black and White interracial couples[END_REF]. We have yet to understand, however, how such relationship marginalization is potentially associated with how partners integrate their cultural and couple identities.

Marginalization can exacerbate inter-identity conflict, and make people feel divided [START_REF] Benet-Martinez | Bicultural Identity Integration (BII): Components and Psychosocial Antecedents[END_REF]Yampolsky & Amiot, 2016). To illustrate, consider a fictitious couple, Noah, who identifies as Jewish, and his partner Karuna, who is West Indian. Noah's parents have expressed that they would not accept the relationship and are distressed that Noah is partnered with an "outsider." In response, Noah has concealed his relationship with Karuna from his family. Noah identifies as Karuna's partner when they are together, but he experiences the disapproval of his intercultural relationship as a psychological barrier to reconciling his relationship with Karuna and his Jewish identity. When Noah is with his parents, his Jewish identity is active, but he suppresses his identity as Karuna's partner. Although Karuna understands Noah's desire to avoid tensions with his family given their disapproval, Karuna experiences Noah's reticence to open up about his Jewish side, or to introduce her to his family as a choice that distances Karuna from this fundamental part of his existence, his cultural identity, and she feels rejected. Karuna also fears that their future together is uncertain if Noah cannot share all of himself with her in their partnership. In our example couple, Noah has been made to feel that the self-descriptions "I am Jewish" and "I am Karuna's partner" are mutually exclusive and divided. The current research proposes that this fragmented and conflicted identity experience may not be isolated to one person in the couple and may also carry over to one's partner in the couple. Since one partner does not have access to all of the important aspects of their partner, they may feel that they are being kept at a distance, which could hinder their relationship satisfaction and desire to invest in and maintain the relationship.

Couple and cultural identity integration in intercultural couples

Our social identities are core facets of who we are. They are how we define ourselves and are inextricably connected to our relationships with others. Cultural identity refers to the sense that one is a member of their cultural group (Amiot, de la Sablonnière, Terry & Smith, 2007), and feels connected to the values and norms associated with their cultural group(s) [START_REF] Phinney | Variations in bicultural identification among African American and Mexican American adolescents[END_REF][START_REF] Schwartz | The structure of cultural identity in an ethnically diverse sample of emerging adults[END_REF]. Couple identity refers to the sense of "we-ness" that develops in a relationship, a shared interpersonal space where both partners construct and experience their connection to each other and define themselves by their belonging to the relationship [START_REF] Fergus | The couple's mutual identity and reflexivity: A systemicconstructivist approach to the integration of persons and systems[END_REF][START_REF] Reid | Therapeutically induced changes in couple identity: The role of we-ness and interpersonal processing in relationship satisfaction[END_REF]. It is a cognitive interdependence involving the perception that "myself" and "my partner" overlap [START_REF] Alea | We-ness" in relationship-defining memories and marital satisfaction[END_REF], as well as the experience of one's social role as a partner (e.g., husband, wife, spouse; [START_REF] Aron | The self-expansion model of motivation and cognition in close relationships and beyond[END_REF][START_REF] Aron | Falling in love: Prospective studies of self-concept change[END_REF]. Interdependence in a relationship is associated with greater marital satisfaction [START_REF] Aron | Inclusion of Other in the Self Scale and the structure of interpersonal closeness[END_REF], and greater couple identity clarity has been associated with greater relationship commitment (Emery et al., 2020). As individuals in intercultural couples become closer, however, they are inevitably confronted by the differences in their cultural worldviews, along with the relationship marginalization of their non-normative pairing (Karis & Killian, 2011). They are thus faced with negotiating the potential discrepancies between their cultural identities and their couple identities.

When a social identity is devalued, there is a greater likelihood for individuals to disidentify with the devalued identity [START_REF] Branscombe | The context and content of social identity threat[END_REF]. Perceived marginalization of one's relationship may put partners in the position of having to choose between their cultural and couple identities, thereby threatening the relationship satisfaction that is associated with a strong couple identity. Past research has shown that when individuals can connect their multiple identities, they experience greater wellbeing, but when their identities are disconnected, they experience lower well-being [START_REF] Yampolsky | The Multicultural Identity Integration Scale (MULTIIS): Developing a comprehensive measure for configuring one's multiple cultural identities within the self[END_REF]. In the context of romantic relationships, partners' ability to integrate their couple and cultural identities may be particularly relevant for relationship quality.

According to the Cognitive-Developmental Model of Social Identity Integration (CDSMII; [START_REF] Amiot | Integration of social identities in the self: Toward a cognitive-developmental model[END_REF], there are several ways that people can integrate or reconcile multiple social identities1 : integration, compartmentalization and categorization. Integration is qualified by having multiple, connected identities that form a cohesive whole; one perceives a common ground between identities, and the differences between identities are seen as advantageous and complementary. Additionally, a superordinate identity can bridge the different identities under a shared umbrella. In the context of intercultural couples, [START_REF] Killian | Interracial Couples, Intimacy, and Therapy: Crossing Racial Borders[END_REF] exploratory qualitative work showed that many couples tend to identify with being human or with a common social identity, such as religion, which can serve as a bridge between their ethnic backgrounds and the formation of their couple. Furthermore, [START_REF] Seshadri | How couples manage interracial and intercultural differences: Implications for clinical practice[END_REF] showed that many couples focused on common points between each partner's cultural backgrounds as a means to unite their cultural and couple identities across social divisions. Identity integration tends to be associated with positive outcomes across cultural and general social identity domains, including well-being (Yampolsky et al., 2016), increased tolerance towards dissimilar others [START_REF] Huff | Bicultural and generalized identity integration predicts interpersonal tolerance[END_REF], and the creation of a common ingroup identity over time [START_REF] Amiot | Social identity change during an intergroup merger: The role of status, similarity, and identity threat[END_REF].

Compartmentalization is characterized by having multiple identities that are kept separate within the self-concept. One identifies with each identity in its respective context (e.g., couple identity), while suppressing the other identity (e.g., cultural identity). In compartmentalization, one identity is not just more salient than the other while in its context, but the other identity is being actively suppressed. The differences between identities are seen as clashing and irreconcilable. Prior work on intercultural couples [START_REF] Killian | Interracial Couples, Intimacy, and Therapy: Crossing Racial Borders[END_REF] found that some couples perceive contradiction between their intercultural couple and their own cultural/racialized background. Compartmentalizing cultural identities is associated with lower well-being (Yampolsky et al., 2016).

Another approach to managing multiple identities is to prioritize one identity. This categorization approach, has one predominant identity with others becoming less central to the self-concept. In the current research, we distinguish between categorization to one's cultural group (culture categorization), where one identifies predominantly with one's culture and excludes the couple identity from the self-concept, and categorization to one's relationship (couple categorization), where one identifies predominantly with one's couple, and excludes their cultural identity from the self-concept. Previous work on intercultural couples found that some interracial couples formed their couple identities by explicitly removing the focus on cultural differences in the couple [START_REF] Killian | Interracial Couples, Intimacy, and Therapy: Crossing Racial Borders[END_REF].

Findings about the consequences of categorization are ambiguous (e.g., [START_REF] Yampolsky | Multicultural identity integration and well-being: A qualitative exploration of variations in narrative coherence and multicultural identification[END_REF], and so examining categorization within the context of the marginalization experience of intercultural couples was exploratory in nature.

The current research is the first to directly investigate identification processes in intercultural couples in the context of marginalization, which acts as an internalized barrier to partners integrating their cultural and couple identities. Previous work has shown that the experience of racism directly predicts greater compartmentalization of one's cultural identities, and indirectly predicts lower integration of these identities (Yampolsky & Amiot, 2016). We therefore expected that marginalization of the intercultural couple would predict greater compartmentalization of one's couple and cultural identities and predict lower integration of these identities.

Identity configurations and relationship quality

To establish the importance of identification in the context of intercultural couples, the current studies also focused on how the identity configurations (integration, compartmentalization, categorization) were associated with relationship quality, specifically relationship investment (the devotion of one's own personal and psychological resources to the relationship), commitment (the psychological attachment to the relationship and the intention to remain with the partner) and satisfaction (the experience of positive affect and attraction with the relationship) [START_REF] Rusbult | Commitment and satisfaction in romantic associations: A test of the investment model[END_REF][START_REF] Sternberg | A triangular theory of love[END_REF]. We know that at the individual-level, more integration is associated with greater personal well-being, and compartmentalization is associated with lower wellbeing [START_REF] Yampolsky | The Multicultural Identity Integration Scale (MULTIIS): Developing a comprehensive measure for configuring one's multiple cultural identities within the self[END_REF]. We expected that the configuration of one's cultural and couple identities would also be associated with their relationship quality. Keeping one's identities separate and context bound may have the effect of minimizing one's degree of couple investment by excluding the relationship from other key parts of their lives. Since people in close relationships often influence each other's attitudes, cognitions, and behaviors [START_REF] Kenny | Methodology in the social sciences[END_REF][START_REF] Rusbult | Why we need interdependence theory[END_REF], a divided identity experience within the self can potentially extend to one's partner, where the partner feels divided from the whole self of their significant other. On the other hand, by integrating a relationship with one's cultural identity, partners are effectively connecting these important pieces of their lives. The work involved in integrating one's identities in the context of the couple is an investment of one's own psychological resources to one's self-definition as a partner.

The Current Studies

Across two studies, we examined how perceived marginalization of one's intercultural relationship predicts both the person's own cultural and couple identity configuration (Studies 1 and 2), as well as their partner's cultural and couple identity configuration (Study 2). We also investigated how a person's identity configurations predict their own relationship investment, commitment and satisfaction (Studies 1 and 2) as well as their partner's relationship quality (Study 2). We predicted that greater marginalization would be associated with lower integration, and greater compartmentalization. We expected integration to be associated with greater relationship investment, commitment and satisfaction, and compartmentalization to be associated with lower relationship investment, commitment and satisfaction. In Study 1, we recruited people in intercultural relationships to test these associations at the individual level. In Study 2, we extended the findings by recruiting intercultural couples2 to test how one's perception of marginalization was associated with a person's own identity configuration and relationship quality (actor effect) as well as their partner's identity configuration and relationship quality (partner effect; see Figures 1 and2). We also tested the generalizability of the findings across relationship duration and bicultural status (for more information see the online supplementary materials).

Study 1 Participants

The sample consisted of 242 participants (104 women, 131 men, 7 other, Mage = 37.16, SDage = 9.99). Participants were recruited via Prolific, a crowdsourcing platform for research. According to participants' self-reported ethnicity, the sample consisted of individuals who were White (70.4%), Black (3.8%), Latinx (9.6%), Native (0.01%), Middle Eastern (0.01%), South Asian (2.9%), East Asian (5.8%), Southeast Asian (0.01%), and Mixed (4.2%). Couples' reported relationship statuses included casual dating (0.5%), long-term dating (2.5%), engaged (3.2%), common law (5.5%), and married (91.5%). The average duration of the relationship was 10 years (M = 10.00 years, SD = 7.97 years).

Measures 3

Descriptive statistics for the following measures can be found in Table 1.

Perceived relationship marginalization.

The extent to which participants perceived social disapproval and exclusion towards their intercultural relationship from their family, friends, and society was measured using the Relationship Marginalization Scale [START_REF] Lehmiller | Marginalized relationships: The impact of social disapproval on romantic relationship commitment[END_REF], consisting of 6 items (α = .76; e.g, "My friends approve of my relationship" (reverse coded)) rated on a 9-point Likert scale ranging from 1 (Not true of my relationship at all) to 9 (very true of my relationship).

Couple and cultural identity configurations. The configuration of one's couple and cultural identities was assessed using four vignettes, one for each configuration:

Categorization to the relationship (R), Categorization to their own culture (C), Compartmentalization of the couple and cultural identities, and Integration of couple and cultural identities. These configuration vignettes were based on the CDSMII model (Amiot, de la Sablonnière, Terry & Smith, 2007). Each vignette provided a brief and illustrative representation of its configuration. Participants indicated the extent to which each of the four configurations represented their experience (1: not at all to 7: exactly).

Relationship investment, commitment and satisfaction. The Investment Model

Scale [START_REF] Rusbult | The Investment Model Scale: Measuring commitment level, satisfaction level, quality of alternatives, and investment size[END_REF] assessed relationship investment (5 items, α = .78; e.g. "I have put a great deal into our relationship that I would lose if the relationship were to end.") and commitment (3 of the 7 original items were selected for brevity, α = .94; e.g. "I want our relationship to last for a very long time.") from 0 (do not agree at all) to 8 (agree completely). Satisfaction was assessed with the three-item subscale (α = .97; e.g. "How satisfied are you with your relationship?") from the Perceived Relationship Quality Components Inventory [START_REF] Fletcher | The measurement of perceived relationship quality components: A confirmatory factor analytic approach[END_REF] on a scale from 1 (not at all) to 7 (extremely).

Results and discussion

Participants reported relatively low levels of relationship marginalization in this sample, and integration was the most highly endorsed of the identity configurations (see Table 1). In line with our predictions, people who perceived greater relationship marginalization from others reported lower integration of their couple and cultural identities. In contrast, people who perceived greater marginalization reported greater compartmentalization as well as greater couple and culture categorization (see Table 1).

Regression analyses were run with all four configurations simultaneously entered to investigate how each identity configuration predicted investment, commitment and satisfaction, respectively, once controlling for the shared variance between the configurations (see Table 2). As predicted, these analyses showed that integration was significantly associated with greater investment, commitment and satisfaction, whereas culture categorization (i.e., identified predominantly with their culture) was associated with lower commitment and satisfaction.

The results from Study 1 suggest that individuals who feel more marginalized are more likely to feel divided and disconnected at the identity level, whether through separating their identities or feeling forced to choose between them. The ability to integrate one's couple and cultural identities is associated with greater relationship quality, while categorization -and to a certain extent compartmentalization -are associated with lower relationship quality.

Study 2

In Study 2, we extend Study 1 by recruiting both members of intercultural couples to investigate the links between marginalization, the couple and cultural identity configurations and both partners' relationship quality, given the mutual, interdependent influence of partners. We predicted that a person's perception of marginalization would predict lower integration and greater compartmentalization for themselves (actor effect) and would also predict lower integration and greater compartmentalization for their partner (partner effect). Moreover, we predicted that a person's integration would predict greater relationship quality for both themselves and their partner, whereas compartmentalization would predict lower relationship quality.

Method

Participants

Two different samples from separate online studies on intercultural couples were combined to increase statistical power 4 . Two hundred and fifty-eight couples (N = 516; 248 men, 261 women, 7 unspecified; Mage = 31.65, SDage = 9.12) currently in a romantic relationship participated in this study. The cultural composition of participants was diverse. Their self-reported ethnicity was as follows: White (56%), Black (6%), Latinx (7%), Native (0.01%), Middle Eastern (3%), South Asian (8%), East Asian (8%), Southeast Asian (4%), and Mixed (7%). Couples' reported relationship statuses included 4 One sample (n=204) recruited couples from the broader community via convenience sampling, snowballing and community outreach. Flyers advertising the study were placed at local parks, community centers, university campuses, and at other popular spots in the city of Toronto. The other sample recruited couples using Prolific (n=312). The inclusion criteria and the key measures were the same, except that the community sample only included heterosexual couples while the Prolific sample was open to couples of all sexual orientations. If one partner in a couple filled out the questionnaire, but the other did not, their data was excluded from the analyses. casual dating (2%), committed relationship (66.7%), engaged (4.9%), cohabiting (8.8%), and married/common law (16.7%).

Measures

The same measures from Study 1 for couple and cultural identity configurations, perceived relationship marginalization, and relationship investment and commitment were used for Study 2. For relationship satisfaction, the community sample used the satisfaction subscale from the Investment Model Scale [START_REF] Rusbult | The Investment Model Scale: Measuring commitment level, satisfaction level, quality of alternatives, and investment size[END_REF], while the Prolific sample used the satisfaction items from the Perceived Relationship Quality Components [START_REF] Fletcher | The measurement of perceived relationship quality components: A confirmatory factor analytic approach[END_REF]. Though two different scales were used to assess satisfaction, the items overlapped in content (e.g., Investment Model Scale: "I am happy with my relationship" and PRQC: "How happy are you with your relationship"). In order to analyze satisfaction in a way that was equivalent across samples, the items from these two satisfaction measures were standardized and the z-scores were combined for analysis (see [START_REF] Webster | An investment model of sociosexuality, relationship satisfaction, and commitment: Evidence from dating, engaged, and newlywed couples[END_REF] for an example of standardization of measures between samples).

Results and discussion

In order to account for the interdependent nature of the data collected from both partners in the intercultural couples in this study, we used Actor-Partner Interdependence Models (APIM) to test our hypotheses. Descriptive statistics for the measures are presented in Table 3. As in Study 1, perceived relationship marginalization was relatively low. Integration was the most highly endorsed identity configuration. Correlations between actor and partner variables are presented in Table 4.

Perceived marginalization to couple and cultural identity configurations

Four APIM analyses were conducted to test the associations between one's own and one's partner's marginalization experiences with each of the four couple-cultural identity configurations (see Table 5). First, consistent with our hypotheses and the results

from Study 1, people who perceived more marginalization reported lower identity integration. We also found that people who perceived more marginalization reported more categorization towards their couple identity, and towards their cultural identity. In addition, when people perceived greater relationship marginalization, their partner also reported marginally higher identity compartmentalization and couple categorization, suggesting that the more a person perceived marginalization toward their relationship, the more their partner kept their identities separate or identified solely with the couple. .90

Note. *These coefficients remained statistically significant after applying the multiple testing correction using the Benjamin-Hochberg procedure [START_REF] Mcdonald | Multiple comparisons[END_REF].

Couple and cultural identity configurations with relationship investment, commitment and satisfaction

As depicted in Table 6, a person's identity configuration was associated with both their own and their partner's relationship quality. Specifically, when people integrated their identities, they reported more investment, commitment, and satisfaction, and their partners reported more investment (and marginally more commitment). In contrast, when people compartmentalized their identities, they reported less commitment and satisfaction, and their partner reported marginally less investment. When people categorized towards their cultural identity, they reported lower investment, commitment, and satisfaction, and their partner also reported lower satisfaction. Note. *These coefficients remained statistically significant after applying the multiple testing correction using the Benjamin-Hochberg procedure [START_REF] Mcdonald | Multiple comparisons[END_REF]. The satisfaction score was created by standardizing the two measures and the z-scores were combined for analysis.

General Discussion

Social marginalization of intercultural relationships can create an unwelcoming environment for intercultural couples, which they may internalize in the form of feeling divided between their cultural identity and their couple identity. The present research investigated how perceived relationship marginalization is associated with couple and cultural identity configurations. Across both studies, perceived relationship marginalization was relatively low, and individuals who reported lower perceived marginalization also reported greater integration between their couple and cultural identities; this suggests that in the absence of marginalization, many intercultural couples are able to connect these core parts of themselves. In contrast, those reporting greater perceived relationship marginalization were more likely to compartmentalize their cultural and couple identities; one's own perceived marginalization was also associatedthough marginally-with their partner reporting greater compartmentalization. Overall, participants' bicultural status and relationship length did not moderate these results (see online supplementary materials). These findings suggest that when people experience a social context of disapproval, their ability to connect their cultural identities with their couple identity may be inhibited, and instead they keep these key parts of themselves separate. This is consistent with past work showing that experiencing racism is associated with compartmentalizing one's multiple cultural identities (Yampolsky & Amiot, 2016).

In addition, the current findings showed that perceived marginalization was associated with both identifying predominantly with one's relationship and identifying predominantly with one's culture; in Study 2 we also found that perceived marginalization was associated, albeit weakly, with a partner solely identifying with the couple. It is possible that social disapproval creates pressure to choose between key parts of oneself as a show of loyalty (e.g., [START_REF] Rockquemore | Socially embedded identities: Theories, typologies, and processes of racial identity among Black/White biracials[END_REF] to either their cultural group or their relationship partner. There may also be a rejection-identification process at work (Branscombe, Schmitt, & Harvey, 1999) in which marginalization towards one's relationship is experienced as rejection from one's cultural group, and fuels a protective identification with one's relationship. It is also possible, however, that identifying predominantly with the relationship gives rise to greater perception of marginalization, which would be more consistent with an identification-attribution model (Gonzalez-Backen et al., 2018). The direction of these links can be tested in future studies.

Most research on identifying with more than one culture has prioritized the examination of high vs. low integration, given that integration is an adaptive identity strategy (e.g., Nguyen & Benet-Martinez, 2013). Here we show that the marginalization experience is not simply associated with lower identity integration, but that it is also associated with people feeling like they need to choose between their identities or to keep them separate. The latter are less adaptive identity experiences. Each of these different identity configurations is its own process with a distinct set of characteristics, mechanisms, and social influences [START_REF] West | More than the sum of its parts: A transformative theory of biculturalism[END_REF]. It is therefore essential to understand how negative social forces contribute to less adaptive identity strategies. In addition to examining the range of identity configuration processes individually, by recruiting both partners in intercultural relationships in Study 2, we revealed that identity configurations are relevant at the relational level as well. That is, perceived marginalization is associated with both partner's identities and a person's identity configuration is associated with both partner's relationship quality.

Identity integration was the most commonly reported identity strategy across both studies, which may be due to our sample reporting lower levels of marginalization.

Overall, the findings suggest that integrating one's couple and cultural identities is associated with greater relationship quality for both partners, whereas compartmentalization and categorization to one's culture were associated with lower relationship quality for both partners. It is possible that if an individual is keeping their cultural identity separate from their relationship identity, their partner may feel rejected or excluded from a core aspect of their partner's life. Future research examining this possibility could inform how one partner's identity configuration is associated with the partner's relationship quality. Interestingly, identifying predominantly with one's couple over one's culture was associated with greater relationship quality in Study 1, but was unrelated to relationship quality in Study 2. While identifying predominantly with one's couple may prioritize the couple and therefore enable one to experience greater relationship quality, it may prove difficult and ambivalent since disidentifying with one's own cultural group, and the possibility of cutting ties with close others from one's cultural group, may come at a significant cost to individual well-being (e.g., [START_REF] Smith | Ethnic identity and personal well-being of people of color: A meta-analysis[END_REF]. Future work can test the potential mediating role of perceived social pressure and divided loyalties.

Limitations and future directions

The current studies are correlational and cannot confirm the causal direction or appropriately test whether identity configurations are a mechanism linking marginalization to relationship quality [START_REF] Pek | On the (in)validity of tests of simple mediation: Threats and solutions[END_REF]. However, these findings indicate that identity integration is meaningful for the success and happiness of intercultural couples and may be one process through which marginalization is associated with relationship quality. Future longitudinal and experimental studies can investigate the identity configurations as a potential mediator between relationship marginalization and relationship quality.

This research focused on intercultural couples, but the identity configurations may also be of consequence to couples who identify with different marginalized social categories aside from culture or racialized groups, such as class or sexual orientation.

These findings may also apply to couples in which partners are navigating important social identities with their relationship identity, such as politically conservative and liberal identities. Future research could examine whether social identity configuration patterns emerge consistently in couples from different social groups more broadly.

There are also limitations to the current studies that should be addressed in future work. The samples primarily represented cis-gendered and heterosexual individuals, and so future samples will endeavor to be more representative of gender and sexual minorities as we examine these identity experiences. In order to continue building a more global psychology of intercultural couples, future research will need to focus on the identity experiences of intercultural couples in non-Western contexts, which may have different norms and histories around intercultural romance. The measure of marginalization, while reliable and robust, is not elaborate in terms of the range of marginalization experiences that the couples experience. Future work needs to dig deeper into all the facets of relationship marginalization of intercultural couples, ranging from disapproval to explicit and implicit racism.

Conclusion

In sum, the current set of studies examines the context of marginalization facing intercultural couples as a factor that is associated with partners' ability to connect their relationship identity with their cultural identity. Across two studies, perceived relationship marginalization was associated with less adaptive identity configuration strategies, and when people reported less integration and more compartmentalization between their couple and cultural identities, both partners in the relationship reported lower relationship quality. Social identities are the parts of a person that represent their connection to their loved ones and groups. For intercultural couples, how partners integrate the cultural and romantic aspects of the self provides insight into the satisfaction and maintenance of intercultural relationships, and the current research suggests that perceived marginalization creates challenges for people in intercultural relationships to integrate their identities and maintain their relationships over time.

  Maya A. Yampolsky is an Assistant Professor at Université Laval. Her research examines how multicultural identification and intercultural relationships are connected to broader context factors such as acculturation, enculturation and racism. Alexandria West is a Postdoctoral Associate at Duke University. Her research tests how the processes biculturals and intercultural couples use to negotiate their cultures affect them psychologically and socially. Biru Zhou is a Research Associate at McGill University. Her research is on interpersonal relationships and social support, as well as sociocultural determinants of mental health. Amy Muise is an Assistant Professor and York Research Chair in Relationships and Sexuality at York University. She studies romantic relationships, sexuality, and motivation.

Figure 1 :

 1 Figure 1: Conceptual model of both actor and partner effects of perceived marginalization to couple and cultural identity configurations.

Figure 2 :

 2 Figure 2: Conceptual model of both actor and partner effects of couple and cultural identity configurations to relationship quality.

Table 2

 2 Study 1: Regression findings for couple and cultural identity configurations to relationship investment, commitment and satisfaction.

			Investment			Commitment		Satisfaction
		B	Std Error [95% CI]	B	Std Error [95% CI]	B	Std Error [95% CI]
	Integration	.22**	.08	[.060, .377] .27***	.07	[.125, .420] .28***	.06	[.161, .409]
	Compartmentalization	.07	.09	[-.105, .255]	-.06	.08	[-.242, .092]	-.02	.07	[-.151, .129]
	Couple categorization	.04	.06	[-.080, .152]	.07	.05	[-.029, .186]	.10*	.04	[.014, .194]
	Culture categorization	-.15 †	.08	[-.321, .009]	-.17*	.07	[-.328, -.022] -.19**	.06	[-.327, -.070]
	Adjusted R 2		.04*			.13***			.16***
	Notes: N=240. *p<.05, **p<.01, ***p<.001. CI = confidence interval.

Table 3

 3

	Study 2: Descriptives for couple and cultural identity
	configurations, relationship marginalization, investment,
	commitment and satisfaction.
		M	SD
	Integration	5.31	1.55
	Compartmentalization	1.79	1.24
	Couple categorization	2.89	1.76
	Culture categorization	2.17	1.36
	Marginalization	2.05	1.20
	Investment	6.87	1.48
	Commitment	8.55	1.01
	Satisfaction	.00	1.00
	Prolific subsample (n = 308)	6.10	1.10
	Community subsample (n = 204)	7.87	1.21

Note: N=510. The satisfaction score was created by standardizing the two measures and the z-scores were combined for analysis. The descriptives for the subsamples are provided. The Prolific subsample was administered the Perceived Relationship Quality Components Inventory (1 to 7 scale), and the community subsample was administered the Investment Model Scale (0 to 8 scale)

Table 5

 5 Study 2: APIM results for marginalization to actor and partner relationship couple-cultural identity configurations.

	Integration	Compartmentalization Couple Categorization	Culture Categorization
	b (SE)	p	b (SE)	p	b (SE)	p	b (SE)	p
	[95% CI]		[95% CI]		[95% CI]		[95% CI]
	Marginalization
	Actor -.21* (.06)	< .001	.21* (.05)	<.001	.17* (.07)	.01	.10 (.05)	.06
	[-.33, -.10]		[.12, .30]		[.04, .30]		[-.004, .20]
	Partner -.08 (.06)	.13	.08 (.05)	.07	.11(.07)	.10	-.007 (.05)
	[-.20, .03]		[-.01, .17]		[-.02, .24]		[-.11, .09]

Table 6

 6 Study 2: APIM results for couple and cultural identity configurations to actor and partner relationship investment, commitment and satisfaction.

	Investment		Commitment		Satisfaction
	b (SE)	p	b (SE)	p	b (SE)	p
	[95% CI]		[95% CI]		[95% CI]

In our current research, we employ three of the four configurations since the anticipatory categorization configuration examines the anticipation of developing a new social identity, while the current study focuses on people who already have these identities.

It should be noted that both studies were part of larger surveys examining multiple variables; in the present research we are reporting the measures that are relevant to the current questions.

The measures for both studies are included in the online supplement document accompanying this article.

Acknowledgments

This research was supported by a Small Institutional Grant via York University from the Social Sciences and Humanities Research Council of Canada (SSHRC), a start-up grant

and a postdoctoral fellowship from the Fonds de Recherche Québécois sur la Société et la Culture (FRQSC) awarded to Maya A. Yampolsky, as well as a SSHRC Insight grant and Canadian Foundation for Innovation grant awarded to Amy Muise, and a SSHRC Insight grant held by Richard Lalonde. The research was also supported by a SSHRC doctoral fellowship and an Ontario Graduate Scholarship awarded to Alexandria West.


Maria A Zuluaga

Ninon Burgos

Andrew M Taylor

Sébastien Ourselin

MULTI-ATLAS SYNTHESIS FOR COMPUTER ASSISTED DIAGNOSIS: APPLICATION TO CARDIOVASCULAR DISEASES

Keywords: Computer-aided diagnosis, image synthesis, MR, heart

Atlas-based analysis methods rely on the morphological similarity between the atlas and target images, and on the availability of labelled images. Problems can arise when the deformations introduced by pathologies may affect the similarity between the atlas and a patient's image. The aim of this work is to exploit the morphological dissimilarities between atlas databases and pathological images to diagnose the underlying clinical condition, while avoiding the dependence on labelled images. To this end, the proposed method is formulated under the principle of atlas-based segmentation but, instead of propagating labels, we propagate image intensities. Using a set of MR atlas databases, each database associated with a clinical condition, synthetic images are generated for a target image. The diagnosis is established by assessing the degree of similarity between the synthetic images and the target and assigning the condition of the top-ranked synthetic image. The obtained results are comparable to state-of-the-art methods using annotated images, with an accuracy of 90.0% when evaluated on a set of 60 whole heart MR images containing healthy and pathological subjects.

INTRODUCTION

Atlas-based segmentation is a well established method for segmenting images. It involves propagating an atlas to a target image and then applying a fusion method to combine the label images of the atlas and finally extract the structures of interest. Despite its popularity, this approach has two major drawbacks. First, to obtain a good segmentation, the morphologi-Joint first authorship This work was supported by the EPSRC (EP/H046410/1, EP/J020990/1, EP/K005278), the MRC (MR/J01107X/1), the EU-FP7 project VPH-DARE@IT (FP7-ICT-2011-9-601055), the NIHR Biomedical Research Unit (Dementia) at UCL and the National Institute for Health Research University College London Hospitals Biomedical Research Centre (NIHR BRC UCLH/UCL High Impact Initiative), the UK National Institute for Health Research (SRF/08/01/018), and an IMPACT studentship funded jointly by Siemens and the UCL Faculty of Engineering Sciences. cal similarity between the atlases and the target image must be sufficient. When this condition is not satisfied, the deformations induced by the morphological dissimilarities may hinder atlas registration, leading to unrepresentative segmentations. This situation is common when pathologies introduce morphological alterations in the affected organs. Second, atlasbased segmentation is strongly dependent on the availability of labelled images. In a clinical scenario or research project with limited resources, gathering a sufficient number of annotated images of pathology-specific, or even healthy subjects, is a challenge.

Different works have tried to address the problem of morphological dissimilarity. Based on the segmentation stage that they tackle, methods can be classified into four categories: atlas construction, atlas or model selection, image registration and segmentation analysis. The first class of attempts proposes to build probabilistic atlases which are flexible enough to include the variations introduced by pathologies [START_REF] Lorenzo-Valdes | Segmentation of 4D cardiac MR images using a probabilistic atlas and the EM algorithm[END_REF]. Model selection techniques aim to select the atlas subset that best fits the target images as to remove potential outliers [START_REF] Cardoso | STEPS: Similarity and Truth Estimation for Propagated Segmentations and its application to hippocampal segmentation and brain parcelation[END_REF]. Methods addressing image registration formulate a registration framework capable of handling images containing large pathologies and large deformations [START_REF] Liu | Low-Rank to the Rescue Atlas-Based Analyses in the Presence of Pathologies[END_REF]. Finally, segmentation analysis methods exploit the segmentation errors caused by poor atlas matching to identify the underlying pathology within the context of computer-aided diagnosis (CAD) [START_REF] Ma | Multi-atlas Based Pathological Stratification of D-TGA Congenital heart disease[END_REF]. A common characteristic of the above mentioned methods is that they do not solve the dependence on labelled images.

In this work, we follow the principle of atlas-based segmentation for CAD but, similarly to [START_REF] Burgos | Attenuation Correction Synthesis for Hybrid PET-MR Scanners: Application to Brain Studies[END_REF], instead of propagating labels, we propagate image intensities. The developed algorithm makes use of pre-acquired databases of magnetic resonance (MR) images, each database comprising subjects presenting a defined pathology. For each target image, a synthetic image is generated from each database. The diagnosis is established by comparing the synthetic images to the target.

METHOD

Following the principle that an unrepresentative atlas is more likely to lead to a poor segmentation [START_REF] Ma | Multi-atlas Based Pathological Stratification of D-TGA Congenital heart disease[END_REF], this work is based on the hypothesis that synthetic MR images generated through atlas-target matching will be more similar to the target when the patient's image and the matched database share the same clinical condition. The proposed method generates synthetic MR images through a multi-atlas information propagation scheme based on local matching of MRI features. For a given patient, we create one synthetic image for each condition using its corresponding dataset. The final diagnosis is established by assigning the condition whose synthetic image is most similar to the true image as measured by a global similarity measure (Fig. 1).

Database preprocessing, inter-subject mapping and object location

Given a set of clinical conditions Ω , an atlas database D ω is defined as the set of N MR images sharing condition ω, ω ∈ Ω. Every image in an atlas database has an associated image mask defining a region of interest (ROI) enclosing the anatomical structure of importance. As opposed to standard atlas-based methods, these masks are not required to be highly precise. They can be, therefore, obtained through simple segmentation techniques and morphological operations (see Section 3.1).

Let I be the target image to be diagnosed. MR synthesis requires the alignment of the N MR images and masks from each atlas database D ω to the target. This inter-subject mapping is achieved through a two-stage registration process. The images are first affinely aligned using a block matching algorithm and then non-rigidly registered using normalised mutual information. The obtained transformations are used to map the N MRI/mask pairs of each atlas database D ω to the target image. Structure location is achieved by fusing the N mapped masks of an atlas database D ω through a voting scheme (voting threshold of 0.8). The resulting set of masks, one per condition ω, is denoted M Ω .

MR Synthesis

Once mapped to the target subject, the atlas images are fused according to their morphological similarity to the target.

Image/Morphological Similarity

The morphological similarity between the target MRI and the set of registered MRIs is assessed using a local image similarity measure, the local normalised correlation coefficient (LNCC). This evaluates the quality of alignment between two images by calculating the correlation between the signals. The convolution-based LNCC, as implemented by Cachier et al. [START_REF] Cachier | Iconic feature based nonrigid registration: the PASHA algorithm[END_REF], between the target MR image I and the n th mapped image of atlas database D ω (J ω n ), at voxel v, is given by:

LNCC n, v = I, J ω n v σ(I) v σ(J ω n ) v . (1)
The means and standard deviations at voxel v are calculated using a Gaussian kernel G σ G with standard deviation σ G through convolution:

I v = [G σ G * I] v σ(I) v = I 2 v -I 2 v I, J v = I • J v -I v • J v ,
where * denotes the convolution operator. As suggested by Yushkevich et al. [START_REF] Yushkevich | Nearly automatic segmentation of hippocampal subfields in in vivo focal T2-weighted MRI[END_REF], registration inaccuracies are compensated using a ranking scheme where larger weight is given to the images better registered to the target image. The LNCC at each voxel is ranked across all atlas images and the ranks, noted as R n v , are converted to weights by applying an exponential decay function:

W n, v = e -βR n v (2)
with W n v being the weight associated with the n th atlas image at voxel v.

Intensity fusion

Similarly to the label fusion framework developed by Cardoso et al. [START_REF] Cardoso | STEPS: Similarity and Truth Estimation for Propagated Segmentations and its application to hippocampal segmentation and brain parcelation[END_REF], the final synthetic MR image is obtained by a spatially varying weighted averaging process. This average is computed within a ROI M , defined as the intersection of each database mask:

M = ω∈Ω M ω . ( 3
)
The fusion is restricted to the intersection to guarantee that the synthetic images generated from the different atlas databases are defined in a common region.

As the MRI intensity scale is not standardised, the images have to be normalised prior to the fusion step. We used a standard score normalisation:

I norm = I -I M σ(I M ) (4)
where the mean and standard deviation are computed within M . In the following, J ω n refers to the normalised image. Finally, the weights W n v are used to reconstruct the synthetic MR image I ω at voxel v ∈ M as follows:

I ω v = N n=1 W n v • J ω n v N n=1 W n v .
(5)

Synthetic image ranking and final diagnosis

Synthetic images are generated for each pathology represented in the databases. Each synthetic image I ω is then compared to the target image I using the normalised correlation coefficient (NCC). Following the idea that morphological similarity can be measured through image similarity, the synthetic images are ranked based on the NCC score. A final diagnosis is established by assigning the condition ω of the top-ranked synthetic image I ω to the target image.

EXPERIMENTS AND RESULTS

In order to assess the clinical utility of the proposed CAD system, we tested its capability to diagnose dextro-transposition of the great arteries (d-TGA), a congenital heart disease in which the two major vessels that carry blood away from the heart are switched. Although the d-TGA is repaired at birth through two different procedures known as arterial switch (ASO) and atrial switch, monitoring of the patients across their life time is crucial. Identifying the anatomical variations caused by the correcting procedures from MR images is a complex task which requires high clinical expertise, and is often missed during screening.

Data

The dataset used for the validation was composed of 60 3D, ECG-and respiratory-gated whole heart MR images acquired on a 1.5 T MR scanner (Avanto, Siemens Medical Solutions, Erlangen, Germany) at Great Ormond Street Hospital (London, UK). The images were classified by a clinical expert into three groups according to their clinical condition: ASO (20), atrial switch (20) and normal controls (20). The three groups of images were used as atlas databases D ω , ω ∈ Ω = {ASO, Atrial, Normal}. Masks were obtained via Otsu thresholding, connected component analysis and morphological operations.

Fig. 2. Top: CAD method confusion matrix. Bottom: Sensitivity, specificity and accuracy of the proposed method and the CAD system reported in [START_REF] Ma | Multi-atlas Based Pathological Stratification of D-TGA Congenital heart disease[END_REF].

Results

Validation was performed using a leave-one-out strategy, comparing the label assigned by the proposed method to the one given by the clinical expert. Figure 2 (top) summarises the results in a confusion matrix. The proposed method identified the normal condition in 19 of 20 images and ruled out the presence of a normal anatomy in 40 of 40 images. Among images flagged as pathological, the method was able to identify the correct underlying pathology in 35 of 40 images (20 of 20 for ASO and 15 of 20 for atrial). Sensitivity, specificity, and accuracy were computed and compared to an atlas segmentation-based CAD method [START_REF] Ma | Multi-atlas Based Pathological Stratification of D-TGA Congenital heart disease[END_REF] (Fig. 2, bottom). Examples of diagnosed images and the corresponding synthetic MR images are shown in Fig. 3.

In order to assess the power of NCC as the similarity measure of choice for image ranking and final diagnosis, we also analysed the NCC computed between every target image and its corresponding synthetic images. The boxplots in Fig. 4 show that NCC values are higher when the target image and the atlas database used to generate the synthetic image share the same condition.

DISCUSSION AND CONCLUSIONS

We propose a CAD method synthesising MR images using a set of pre-acquired, pathology-specific, databases, which are then compared to the target image via an image similarity measure. The diagnosis of the target image is obtained by selecting the clinical condition of the top-ranked synthetic image, i.e the synthetic image being, morphologically, the most similar to the target. The proposed CAD method has been evaluated for the classification of d-TGA congenital heart disease. Its overall system accuracy is of 90.00% in the discrimination among d-TGA variations. These results are comparable to those obtained with the segmentation-based method reported by [START_REF] Ma | Multi-atlas Based Pathological Stratification of D-TGA Congenital heart disease[END_REF]. However, our approach is more robust and has the advantage of not depending on previously annotated labelled images. As can be seen in Fig. 2 (bottom), the observed performance of the CAD system in [START_REF] Ma | Multi-atlas Based Pathological Stratification of D-TGA Congenital heart disease[END_REF] could drop up to 10% depending on its configuration. Misdiagnosed cases can be explained by the reliance on a global similarity measure to provide a final diagnosis. The global NCC score might not be able to capture morphological differences caused by the pathology if they are too subtle or it might capture differences in regions that are not relevant for the diagnosis. Strategies to overcome this limitation could include using the NCC value (as opposed to only using its rank) for the classification and adding local similarity metrics. This paper is focused on congenital heart disease applications, but the principle can be applied for the diagnosis of pathologies in different organs. Further experiments are required to validate the method in other regions of the body.

Fig. 1 .

 1 Fig. 1. MR synthesis for computer-aided diagnosis. Synthetic images are generated from the target image for each atlas database presenting a specific condition (red, green, and blue). The diagnosis corresponds to the condition of the synthetic image most similar to the target image.

Fig. 3 .Fig. 4 .

 34 Fig.3. For every target (first column), synthetic MR images (sMR) are obtained using three atlas databases: ASO, atrial and normal. Arrows point to areas where morphological differences between the atlas databases and the target produce anatomically inconsistent images.