Self-Expansion Model

The self-expansion model, developed by Arthur and Elaine Aron, starts from a simple motive: people want to grow, to expand who they are, what they can do, and how they see the world, and close relationships are one of the main ways they do it. Falling in love rapidly expands the self, you take on a partner's perspectives, resources, and identity as partly your own, which is part of why early love feels so exhilarating. The model captures this with the idea of including the other in the self, the sense that the boundary between you and a partner blurs.

The practical heart of the model is what happens after the early rush. Once two people have absorbed each other, the rate of expansion slows, and relationships can settle into boredom, not conflict but flatness. The Arons' answer is that couples can keep expanding together by sharing novel, challenging, and exciting activities, which restores some of that growth feeling and, in their studies, lifts relationship quality. Do new things together, and the relationship feels more alive.

The science here is solid. The model's core measure, a single-item picture scale of how much you include a partner in your sense of self, is validated and has been independently confirmed, and the finding that shared novel and arousing activities improve relationship quality comes from real experiments plus an independent trial. A representative longitudinal study found that boredom at year seven predicted lower satisfaction nearly a decade later. One popular offshoot is weaker than its fame: the viral claim that a set of 36 questions can make strangers fall in love overstates a study that only generated temporary closeness, not love. The model itself is genuinely well supported.

Key insight

The useful idea is that relationships need growth, not just maintenance. A lot of long-term flatness is not a sign that something is wrong, but that two people have stopped expanding together; they have absorbed each other and settled into routine. The fix is not more date nights doing the same thing, but shared novelty, new and slightly challenging experiences that make the relationship a source of growth again. The deeper point is that you can gauge how close you feel by how much your partner has become part of your own sense of self, and that keeping that growing, rather than assuming early closeness lasts on its own, is part of what keeps a long relationship alive.

How to apply

Do new things together, not just familiar ones. The model's most testable advice is to share novel and a little challenging experiences, since these recreate the growth feeling that early love delivered for free. A class you both find slightly hard, travel somewhere unfamiliar, a project that stretches you, all beat another evening of the usual routine. The key ingredients are newness and a bit of challenge, not expense.

Read boredom as a signal, not a verdict. If a relationship feels flat rather than conflicted, the model suggests the issue is stalled expansion, not lost love. That reframes the fix: inject growth rather than assume the relationship has failed.

Keep growing as individuals too. A partner who is pursuing their own development brings new things back into the relationship and stays interesting, so supporting each other's separate growth feeds the shared kind. And skip the hype around the 36 questions as a love potion. The underlying closeness exercise is real and can deepen a connection, but it builds closeness, it does not manufacture love, so use it as a way to go deeper with someone, not as a shortcut.

Criticisms

The core of the model is well supported, but a few cautions apply. Much of the foundational work comes from the Arons' own lab, which makes independent replication especially valuable; the good news is that the key measure and several findings have been confirmed by other researchers, which is why the rating is high. The activities research, while backed by real experiments and an independent trial, tends to use small samples and short follow-ups, and it is hard to fully separate the benefit of novelty from the benefit of simply spending positive time together, so the specific self-expansion mechanism is plausible but not airtight. The biggest overreach is not the Arons' fault: the popular claim that 36 questions make strangers fall in love stretches a study that produced temporary closeness in a lab, not romance or lasting bonds, and that framing traces to a magazine essay rather than a research result.

Origin

Arthur Aron and Elaine Aron, social psychologists, developed the self-expansion model in the 1980s and 1990s, proposing that the drive to expand the self motivates much of human relationship behavior. They created the Inclusion of Other in the Self Scale to measure relational closeness and ran the experiments linking shared novel activities to relationship quality. Their fast-friends procedure, a set of escalating personal questions, later became famous in a stripped-down form as the 36 questions, though its original purpose was studying closeness, not romance.