Practise including the other person in your self-concept
Close relationships develop when you genuinely incorporate the other’s perspectives and resources into how you think — not just spend time with them.
Why it works
Aron’s model holds that closeness is operationally defined as the degree to which a person incorporates the other into their self-concept — borrows their perspectives, skills, and identity. This is not metaphor: research using reaction-time paradigms shows people are slower to distinguish self from close-other attributes the closer the relationship. Practices that deliberately invoke the other’s perspective strengthen this inclusion and deepen the experience of closeness.
How to do it
- When facing a decision, deliberately invoke the perspective of a close person: "How would [name] see this situation?"
- Describe a close person’s strengths or capabilities as though they were resources you have access to.
- In conversation, look explicitly for what the other person knows or does well that you do not — and ask about it.
Evidence
Research using the Inclusion of Other in the Self (IOS) scale found it to be a reliable predictor of relationship closeness, and experimental work found that people’s self-description processing is slower on attributes shared with close others, consistent with the self-incorporation mechanism. (observational)
The self-incorporation mechanism is measured through reaction-time and self-report proxies; whether deliberate IOS-raising practices produce closeness has less direct study than the correlation evidence.
Sources
- Aron, Aron & Smollan (1992), "Inclusion of Other in the Self Scale and the structure of interpersonal closeness", Journal of Personality and Social Psychology
Common mistake
Assuming shared time automatically produces self-expansion — time together without genuine curiosity about the other’s distinct perspective does not produce the inclusion-in-self mechanism.
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More practices for Self-Expansion Model: How Relationships Grow (and Stagnate) Us
- Do novel, moderately challenging activities together
New and slightly difficult shared experiences restore the self-expansion that keeps closeness alive.
- Pursue personal growth that you share — not parallel but joint
Growing alongside a partner or friend, rather than separately, leverages the self-expansion mechanism for both people simultaneously.
- Audit current relationships for expansion rate
Relationships that stopped expanding tend to feel stagnant — a periodic audit reveals where the growth has stopped.
- Use structured escalating self-disclosure to accelerate closeness
Closeness can be deliberately generated through mutual, gradually deepening disclosure — not just through time.
- Protect expansion by resisting the slide into pure comfort
Long relationships naturally slide toward comfort and predictability — expansion requires deliberate re-injection of novelty.
- Apply the self-expansion framework to individual growth, not only relationships
The same motivation that drives relational closeness also drives individual meaning — seeking growth for its own sake.