Theories of love

“Relationships with others are central to the human experience: we are born into them, live through them, and their impact continues even after we die, influencing the lives of those who remain.” (Berscheid, 1999, as cited in Finkel et al., 2017).

In this review, we delve deeper into the main theories of relationship science, focusing on romantic relationships as a topic of interest. In our theme announcement of Research Programme 2025/2026 (Hugs and Hypotheses: Psychology of Close Relationships), we mentioned that the three most influential theoretical frameworks are Interdependence Theory, Attachment Theory, and Sternberg’s Triangular Model of Love (Finkel et al., 2017). These theories of love provide valuable insights into the complexities of human relationships, exploring how individuals form, maintain, and evolve emotionally close bonds. 

Firstly, we will introduce the Interdependence theory. It originated as a game-theoretic model of interactions that seeks to explain close relationships between two people. It was first applied to close relationships in the 1970s, becoming a leading theory by the 1980s. 

It posits that relationship processes and outcomes vary according to various dimensions present in social contexts. For instance, if a man is more dependent on his girlfriend for positive experiences, he will likely pay closer attention to her behaviour for signs of love and commitment. This high dependence places him in a low-power position unless she is equally dependent on him. Generally, high mutual dependence encourages cooperation when partners have shared interests but can lead to conflict when their interests diverge. Interdependence theory suggests that relationship satisfaction increases when outcomes (rewards minus costs) surpass one’s comparison level. It emphasizes the significance of the comparison level for alternatives, which refers to the potential outcomes outside the current relationship. Individuals who perceive their alternatives as more appealing are more likely to experience relationship dissatisfaction and consider leaving. Partners often respond to these perceived alternatives by downplaying or derogating them to protect their current relationship. This cognitive dissonance occurs when individuals feel committed to a partner and view non-chosen alternatives as less desirable. However, relationship structures like polyamory challenge this notion, as individuals may maintain multiple loving relationships without viewing them as direct replacements for one another (Finkel et al., 2017; Stangor et al., 2014). The key concepts of Interdependence Theory include:

• Actor Control: The impact of each person’s actions on their outcomes.

• Partner Control: The impact of each person’s actions on their partner’s outcomes.

• Joint Control: The impact of the partners’ joint actions on each person’s outcomes.

• Covariation of Interests: The extent to which the partners’ outcomes are correlated.

These concepts help analyse the structure of interpersonal situations as well as the degree and type of dependence between individuals, which influences their interactions and relationships. By analyzing the structure of interdependence, the theory offers insights into behaviours that may seem irrational from an individual perspective, such as persistence in unsatisfying relationships or responses to misunderstandings (Rusbult et al., 2008).

Another critical theory is the Attachment theory. Bowlby initially explored infant-caregiver relationships, focusing on attachment, separation, and loss. In the 1980s, his work was adapted to explain adult relationships and became a key model by the 1990s. The theory posits that humans have an inherent need to form and maintain emotional bonds, particularly with romantic partners. Individuals seek closeness to their primary attachment figure, especially in times of stress, illness, or fear, relying on the security this person provides to them. Attachment theory proposes that how individuals are treated by significant others throughout their lives, especially during childhood, shapes their internal working models of self and others. These models guide their thoughts, feelings, and behaviours in future interpersonal contexts, particularly stressful situations. 

Attachment styles vary along two dimensions of (in)security: a) anxiety, which reflects how much reassurance individuals need about their partners’ love and commitment, and b) avoidance, which indicates how uncomfortable they are with emotional intimacy. Secure people—scoring low on both dimensions—tend to exhibit the most constructive relationship behaviours and achieve the best outcomes. They have experienced nurturing care and develop a positive sense of self and others, leading to constructive behaviour towards their partners, especially during conflicts. In contrast, anxiously attached individuals, who score high on anxiety and low on avoidance, have faced inconsistent care and develop negative self-views that make them hypervigilant to signs of partner withdrawal. 

Avoidantly attached individuals, who score high on avoidance and low on anxiety, have experienced rejection and tend to view others as uncaring, leading them to prioritize self-reliance, particularly in stressful circumstances. Fearfully attached individuals, who score high both on anxiety and avoidance, do not feel they deserve love and have an intense fear of relationships, which may come from childhood trauma, abuse, or neglect. 

Furthermore, attachment theorists argue that there are three behavioral systems: the sexual mating system, the attachment system, and the caregiving system. These three behavioural systems are associated with pair bonding, which develops at different rates, with the sexual mating system being crucial early on. In contrast, attachment and caregiving systems become more significant as the relationship matures. 

The assessment of attachment security has evolved with various measures being developed and validated, including narrative interviews, self-report measures, and attachment script-based assessments (Thompson et al., 2022). Lately, Fraley et al. (2019) emphasized that attachment styles are more flexible during childhood and adolescence, making them susceptible to various influences. This flexibility means that early experiences do not rigidly determine adult outcomes; instead, there is potential for change throughout life based on ongoing relational experiences. They stress the importance of studying how different relationship contexts can lead to shifts in attachment patterns. Additionally, while early experiences are significant, understanding adult attachment may require focusing on recent interpersonal interactions. The authors further suggest that genetic factors might contribute to attachment styles, although identifying specific genetic influences has proven challenging (Finkel et al., 2017; Fraley & Roisman, 2019; Gabbard & Rachal, 2012; Stangor et al., 2014). 

Furthermore, research should enhance the representation of various ethnic minorities, particularly African American researchers and participants in the U.S., and focus on how caregivers’ racial-ethnic socialisation relates to secure base provision. For instance, it is crucial to incorporate perspectives from Black youth development and consider the unique contextual factors affecting African American families, such as the intergenerational trauma of slavery (Stern et al 2022). Attachment research should also emphasize other ethnic minorities across different continents. 

Finally, Robert J. Sternberg’s Triangular Theory of Love identifies three key components of love: intimacy, passion, and decision/commitment. These components interact to form different types of love and influence relationship satisfaction. His key findings highlight the importance of perceptions regarding partners’ feelings, the role of ideal versus real partners, and the dynamics of love over time. He categorizes love into eight types and emphasizes the complexity of love, suggesting that successful relationships require ongoing efforts to maintain intimacy, passion, and commitment. Different combinations of these elements lead to various forms of love—like infatuation (passion only) or companionate love (intimacy and commitment without passion), as indicated in Figure 1. All the different types of love identified in the triangular theory include:

• Nonlove: This refers to the absence of all three components of love: intimacy, passion, and commitment. Nonlove characterizes most of our interactions, which are casual and do not partake of love at all.

• Liking: Liking results when one experiences only the intimacy component of love without passion and commitment. It involves feelings of closeness and warmth, often found in friendships 

• Infatuated love: This type of love is characterized by passion without intimacy or commitment. It is akin to what Tennov (1979, as cited by Sternberg, 1986) calls “limerence” and can be pretty lasting under certain circumstances. Infatuated love is often intense and driven by physical attraction.

• Companionate love: This type involves intimacy and commitment without passion. It is often seen in long-term relationships where physical attraction has diminished, but a deep bond and commitment remain, such as in some marriages or close friendships.

• Fatuous love: This type is characterized by passion and commitment without intimacy. It often occurs in whirlwind romances, where a commitment is made based on passion without the stabilizing element of intimacy, making such relationships vulnerable to termination. 

• Consummate love: Consummate, or complete, love results from the combination of intimacy, passion, and commitment. It is the ideal form of love that many strive for in romantic relationships. However, attaining consummate love does not guarantee permanence, as maintaining it can be challenging.

Over time, research shows that while intimacy and passion may decline, commitment strengthens, highlighting a shift in relationship dynamics as they mature. While these evaluative constructs are distinct, they frequently share considerable variance and form a broad dimension reflecting overall relationship quality. The triangular theory of love posits that relationship quality improves when there is a smaller gap between ideal and actual experiences of love components—intimacy, passion, and commitment. Also, perceptions of a partner’s feelings significantly impact relationship satisfaction. It has been found that one’s perceptions of the other’s feelings toward oneself matter for satisfaction at a level roughly comparable to one’s feelings toward the other. Specifically, the strongest predictor of relationship satisfaction is the difference between how the partner perceives the self and how the ideal partner feels about the self. When there is a discrepancy between the perceived and ideal feelings, it can lead to dissatisfaction in the relationship. The triangular theory of love provides a framework for understanding the nature of love in everyday life, integrating various relationship-based phenomena into a cohesive understanding of love (Stangor et al., 2014; Sternberg, 1986).