Key Studies of Relationship Change: How Relationships Grow, Shift, and End 💬

Introduction

In IB Psychology SL, Psychology of Human Relationships explores how people form, maintain, and sometimes end relationships. One important part of this topic is relationship change, which means the ways relationships develop over time. students, think about how friendships can become closer, romantic relationships can start strong and then weaken, or couples can stay together because of shared goals, habits, or investment. These changes are not random. Psychologists have studied them using theories and research methods that help explain why relationships move forward, stay stable, or break down.

In this lesson, you will learn the main ideas behind key studies of relationship change, the terminology used to describe them, and how to apply them in IB-style answers. You will also see how these studies fit into the broader topic of human relationships. By the end, you should be able to explain important models, use research evidence, and connect relationship change to real-life situations such as dating, marriage, friendships, and long-term commitment 😊

Relationship Change: The Big Idea

Relationship change refers to how relationships develop across time. A relationship may begin with attraction and uncertainty, move into deeper commitment, and later either stabilize or end. Psychologists study this process because relationships affect well-being, identity, support, and stress levels.

A very important idea is that relationships are often studied as a process, not a fixed state. This means researchers ask questions like:

Why do some relationships become stronger over time?
Why do some couples stay together even when satisfaction drops?
Why do some relationships end after conflict or distance?

One famous approach is social exchange theory, which says people evaluate relationships by comparing rewards and costs. Rewards may include love, support, and fun, while costs may include conflict, effort, and stress. If the balance seems positive, people are more likely to stay. Another important idea is the comparison level, which is a person’s expectation of what they deserve in a relationship. If the relationship falls below this standard, dissatisfaction may grow.

A related term is comparison level for alternatives, which means how a person thinks other possible relationships would compare. If someone believes they could do better elsewhere, they may be more likely to leave. These ideas help explain relationship change because people do not only look at what they have now; they also think about what they expect and what else is possible.

Key Study 1: Rusbult’s Investment Model

One of the most important studies in relationship change is Rusbult’s Investment Model. This model explains why people remain in relationships, even when satisfaction is not very high. It extends social exchange theory by showing that commitment depends on three main factors: satisfaction level, quality of alternatives, and investment size.

Satisfaction level: how happy someone is in the relationship.
Quality of alternatives: how good other options seem.
Investment size: what someone has put into the relationship, such as time, shared memories, money, emotional effort, or children.

According to this model, commitment is strongest when satisfaction is high, alternatives are poor, and investment is large. This helps explain why some couples remain together through difficult times. For example, a married couple may argue often, but they may stay together because they have built a life together, share responsibilities, and believe no alternative relationship would be better.

Rusbult and colleagues supported the model with research showing that people who felt more committed were more likely to forgive a partner, protect the relationship, and respond constructively to problems. This matters for relationship change because commitment is not just about liking someone in the moment. It is about the long-term pattern of staying, investing, and adjusting.

A useful IB term here is commitment, which means the intention to maintain a relationship over time. Another is dependence, which means how much a person relies on the relationship for emotional or practical support. When dependence is high, relationship change may be slower because leaving would feel costly.

Key Study 2: Duck’s Phase Model of Relationship Breakdown

While some relationships grow stronger, others break down. Duck’s Phase Model of Relationship Breakdown explains this process as a sequence of stages. It is especially useful because it shows that relationship ending is often gradual, not sudden.

Duck proposed four phases:

Intrapsychic phase – one partner starts thinking that the relationship is not working. They may feel dissatisfied but have not yet spoken to the other person.
Dyadic phase – the couple discusses the problems. Communication becomes open, and conflict may increase.
Social phase – friends and family become involved. The relationship may be discussed publicly, and others may take sides.
Grave-dressing phase – after the breakup, each person creates a story to explain what happened. This helps them protect self-esteem.

This model is important because it shows that relationship change involves thoughts, communication, and social context. For example, students, imagine two friends who spend less time together after a major disagreement. One friend first feels unhappy privately, then starts a difficult conversation, then tells other friends about the conflict, and later explains the breakup as “for the best.” That is relationship change in action.

The grave-dressing phase is especially interesting because people often reshape the story of a relationship after it ends. They may blame the other person, minimize their own role, or present themselves in a positive light. This can affect emotional recovery and future relationships.

Key Study 3: Knapp’s Stages of Relational Development and Deterioration

Another useful model is Knapp’s Stages of Relational Development and Deterioration. This model explains both how relationships begin and how they fade away. It is often used to show that relationship change is not just about breakup; it includes development too.

The development stages include:

Initiating: making first impressions.
Experimenting: asking questions and finding common interests.
Intensifying: increasing emotional closeness.
Integrating: becoming a known couple or close pair.
Bonding: making a formal commitment.

The deterioration stages include:

Differentiating: noticing differences between partners.
Circumscribing: communication becomes limited.
Stagnating: the relationship feels stuck.
Avoiding: partners reduce contact.
Terminating: the relationship ends.

This model is helpful because it gives a clear structure for describing change over time. For example, a friendship may move from experimenting to intensifying as two students talk daily and share secrets. Later, if they stop communicating and avoid each other, the relationship may move toward termination.

Knapp’s model is especially useful in IB answers because it provides terminology that can be applied to many real-world cases. However, it is important to remember that not every relationship follows these stages exactly. Some relationships move back and forth, and some end without passing through every stage.

Applying the Studies in IB Psychology SL

To score well in IB Psychology, students, you need to do more than define terms. You must apply them to situations and connect them to the question asked. When discussing relationship change, a strong answer usually includes:

a clear explanation of the theory or study,
relevant terminology,
real-life or research evidence,
and a link back to the question.

For example, if asked why a couple stays together despite problems, you could explain Rusbult’s Investment Model and mention that high investment and few attractive alternatives increase commitment. If asked how relationships end, you could use Duck’s model to describe the gradual stages of breakdown. If asked to explain how a friendship develops and later weakens, Knapp’s model can show both growth and deterioration.

A strong IB response may also compare models. Rusbult focuses on commitment and decision-making, Duck focuses on breakdown stages, and Knapp covers both development and deterioration. Together, they show that relationship change is shaped by personal evaluation, communication, and social influence.

Connection to the Wider Topic of Human Relationships

The key studies of relationship change are part of a larger topic because they explain how relationships affect people’s lives. Relationships are linked to support, identity, stress, and social belonging. When a relationship improves, it can increase well-being. When it ends badly, it can lead to sadness, anger, or loneliness.

These studies also connect to communication, since many relationship changes happen through conversation or the lack of it. They connect to group dynamics because friends, family, and social networks can influence whether a relationship stays together or ends. They also connect to prosocial behaviour and social responsibility because partners often support each other, make sacrifices, and act in the interest of the relationship.

In other words, relationship change is not just about romance. It is about how humans maintain bonds, make choices, and respond to social pressures across many kinds of relationships.

Conclusion

Key studies of relationship change help psychologists explain why relationships develop, stay stable, or end. Rusbult’s Investment Model shows how satisfaction, alternatives, and investment shape commitment. Duck’s Phase Model explains breakup as a gradual process with psychological and social stages. Knapp’s model shows both relationship development and deterioration in a clear sequence. Together, these studies give students a strong foundation for understanding relationship change in IB Psychology SL. They also show that relationships are dynamic, influenced by thought, communication, and social context. By using these theories and research examples, you can better explain real-life relationships and answer IB questions with confidence 📘

Study Notes

Relationship change means the way relationships develop, stabilize, or end over time.
Social exchange theory explains relationships through rewards, costs, and comparisons.
Comparison level is what someone expects from a relationship.
Comparison level for alternatives is how attractive other options seem.
Rusbult’s Investment Model says commitment depends on satisfaction level, quality of alternatives, and investment size.
Duck’s Phase Model describes breakup through the intrapsychic, dyadic, social, and grave-dressing phases.
Knapp’s model includes stages of development and deterioration in relationships.
Relationship change is influenced by communication, commitment, social support, and perceived alternatives.
In IB answers, define terms, apply them to a real example, and link back to the question.
These studies connect to the wider topic of human relationships because they explain bonding, conflict, and social belonging.