From an interpersonal perspective, interactions are believed to naturally develop between couples as the behaviors of one elicit or suppress the behaviors of the other [8]. More recently, the behaviorally oriented relationship theory has hypothesized that relationship success or failure is based on how a couple interacts with one another [9]. According to this perspective, the environmental setting is secondary to how each individual behaves toward the other.

The conflict associated with the earliest developmental stage is trust versus mistrust [20]. At this stage, infants rely on their mother (or other caregiver) to provide comfort. If this is provided, infants develop a sense of trust, which is considered the first relationship milestone, providing a physiologic understanding of the importance of relationships and interdependence. This stage of psychosocial development has been replicated in research and referred to as primary attachment [11]. Primary attachment begins with an infant's initial connection to her or his parent, and its success helps the child adjust to future relationships. If mistrust develops, this can have negative consequences that can impact an individual's future relationships [20].

From a healthy relationship perspective, successful resolution of the main conflict of the next stage (young adulthood), intimacy versus isolation, is the culmination of all previous stages. According to Erikson, the ability to establish and maintain close, intimate, and committed relationships during this stage is central [20]. One's ability to be intimate with others is heavily dependent on early bonding, established confidence, and goal achievement, all of which are established in earlier stages. If the conflicts of previous stages are not successfully resolved, healthy relationships become difficult.

As noted, adequate relationship role models are beneficial in every stage [11,20]. Research has examined the impact of marital conflict on child attachment through specific parent and child behaviors [15]. Parental behaviors that have been found to affect child attachment include how marital problems are communicated and resolved and the degree of responsibility one assumes during conflict [3,15]. Researchers also evaluated sensitive behaviors such as promptness and appropriateness of parental responses to the child.

Several other correlations between attachment behaviors and marital conflict have been identified [15]. Specifically, current marital conflict is negatively correlated with perceived sensitive interactions and positively correlated with perceived parenting attitude with mothers. Also, the degree of attachment between mother and child is correlated with positive interactions. Father-child attachment has been found to be influenced by the degree of marital conflict, which is negatively correlated with both positive parenting attitudes and marital discord. The unfortunate outcome of insecurely attached children is potential lifelong difficulties with interpersonal relationships [15,20,21].

Other theories have focused less on the foundation of attachment and relationship role models and more on present intimate relationships. Despite marriages and long-term relationships having existed for thousands of years, it was not until Sternberg wrote about the three components of love that essential components of healthy relationships were delineated [2]. According to Sternberg and his Triarchic Theory of Relationships, a healthy long-term relationship is comprised of adequate levels of intimacy, passion, and commitment [2]. The level of each of these components fluctuates depending on the type and duration of the relationship. That being said, certain types of relationships are more likely to be healthy and span time. Companionate love is a relationship that is high in both intimacy and commitment but low in passion. Although physical attraction, or passion, may have decreased, the couple will likely stay together in the long term. The other types of relationships are liking (only intimacy), empty love (only commitment), infatuation (only passion), fatuous love (passion and commitment), and romantic love (intimacy and passion); these types are less likely to be lasting unless they evolve. According to Sternberg, the healthiest relationship is one of consummate love, in which intimacy, passion, and commitment are equally strong [2]. However, consummate love is not the end of the journey. Indeed, to have a relationship of consummate love is one of attainment and maintenance. A relationship of consummate love acknowledges commitment while maintaining positive emotions and being mindful of how one communicates during conflict [2,22].

Another intervention for developing successful relationships despite being insecurely attached is attachment-based family therapy. Although this treatment was originally designed for families and individuals who experienced adolescent depression and suicide, it has also been suggested for fostering healthy relationships [19,24]. Attachment-based family therapy assists group participants in processing past and present relationship conflicts that reinforce mistrust and insecurity. Therapy can then move into individual competency and independence. The goal of this type of therapy is to decrease isolation, increase self-esteem, and instill relationship hopefulness [19].

Historically, the majority of research on couples has focused on conflict as the primary, and sometimes sole, predictor of relationship outcomes [7]. However, research has also shown that approaching a relationship from a positive affective state is important, even during conflict. Neurologic studies indicate that approaches to tasks or events are influenced by a positive affective state [25]. For example, a frustrated or sad member of a couple may interpret seemingly neutral communication and conflict as his or her own shortcoming. Positive affect is instrumental in minimizing the magnitude and duration of conflict. This has been illustrated in studies of couples engaged in a positive, approach-oriented interaction task [7,43].

A study involving 119 newlywed heterosexual couples assessed their approach to conflict six months and again one year after their weddings [7]. For the initial meeting, couples individually completed measures focused on their overall perception of the relationship. Then, the couples were asked to briefly discuss an issue as if they were at home. Participants completed measures of how each felt after the discussion. Finally, the couples were separated and asked to focus on their positive feelings toward their partner and then reunited to discuss these feelings. After the first session, researchers categorized the couples as either approaching conflict from a positive place of affection or from a negative place of contempt and predicted that those with a positive approach would perceive more marital satisfaction and be less likely to divorce. After one year, approaching conflict from a positive place had a positive correlation with marital satisfaction and a negative correlation with divorce [7]. However, there was a subjective threshold in that the magnitude of the conflict was a consideration. In other words, approaching an abusive relationship from a place of forgiveness, optimistic expectations, positive thoughts, and kindness was more harmful than helpful [26].

A successful relationship can be more than just the interaction between two partners. Specifically, factors such as genetics and self-talk also play a role, and relationship success is often heavily dependent on the perceptions of each individual [3,15,16,29]. For example, placing blame is a source of relationship discord, while focusing on the overall strengths of one's partner is a factor in relationship success [3]. This can be complicated by each member of the couple's unique perspective, perceptions, and interpretations of the same situation [4,5]. From an internal perspective, an individual in a healthy relationship assumes responsibility for modifying his or her dysfunctional expectations and beliefs. From an external perspective, how one interprets the actions of the other, likely based on causal inferences from many sources, influences how she or he behaves [30].

The concept of filters was outlined in the original PREP program. According to PREP, filters develop from a gradual build-up of uncommunicated interpretations [4,5,27]. Several types of filters were identified: distractors, emotional arousal, need for self-protection, differences in style, and acquired beliefs (e.g., cultural, family of origin) [27]. Distractors result when one partner is only partially attentive while the other is speaking. Within the environmental dynamics of daily life, there are many internal and external distractors, including children, television, and work. Couples who communicate adaptively tend to provide their undivided attention to each other.

The fact that the majority of research on couples focuses on conflict as the primary or sole predictor of relationship outcomes is a deficiency in relationship research [7]. Another shortcoming of relationship research is that much of it has been based upon a younger, White, heterosexual population [22,33]. As society has evolved, so have the difficulties in concretely identifying cultures, especially as they become increasingly blended [4]. Evidence-based therapeutic interventions for couples tend to be more appropriate for middle-class White clients than those from lower socioeconomic statuses and other cultures [9,33]. Mental health clinicians are at risk for making decisions based on stereotypes when working with certain populations, and this can hinder the effectiveness of therapeutic interventions [4].

As such, it is important to consider the cultural implications of what might be defined as a healthy relationship when working with a couple. From the earliest of relationships, studies have noted differences in how children from under-researched populations attach to their parents. For instance, in a study of parental attachment, gender differences, and the influence of race in a sample of African American and White college students, assessments were used to rate perceived parental bond, competencies in relationships, and the overall emotional stability of the participants [29]. The researchers found some differences in the way African American and White participants perceived attachment [29]. If attachment bonds were strong, the relational competencies of the participants were strong, regardless of race. However, definitions of attachment differed between races. While both groups reported that overall perceived parental relationships were stronger for fathers, the degree of attachment was stronger in the African American population compared with the White group. This may have been indicative of how attachment is evolving, as past literature and theory cited more of a maternal bond [11,13,16,40].

From a therapeutic perspective, working with diverse populations in established, loving relationships poses some challenges. Even the results of certain relationship studies with diverse populations may be suspect. Research findings should be cautiously interpreted due to the possibility that participants act differently during the study than in their natural settings [33].

Despite the lack of research focusing on relationships in specific populations, it is still important that clinicians develop cultural competence. This involves being self-aware of cultural differences and adapting accordingly to clients [41]. Cultural competence also consists of therapists seeing the individual within his or her culture, as opposed to seeing the culture and then the individual [4]. From a more global perspective, practitioners should consider how marital behaviors are displayed in collectivistic (e.g., Chinese), as opposed to individualistic (e.g., American), cultures. Couples from individualistic cultures tend to be more open with expressions of affection, while those from collectivistic cultures are not [34].