IKEA Effect

Building something yourself and that thing actually being good are two different facts. The person who built it is the one person least able to tell them apart.

September 9, 2026 7 min read

A team keeps defending a homegrown internal script that breaks roughly once a month, over a purpose-built tool that does the same job without breaking. Ask why, and the reasons offered are usually about flexibility, about knowing exactly how it works, about not wanting to be locked into someone else's assumptions. Ask a harder question, whether the script actually produces better outcomes than the tool, and the reasons get thinner fast. The real answer usually isn't about which one works better. It's that one of the two, they built with their own hands.

The effort that goes into something is not evidence about what it's worth

These are two separate facts about the same object, and it's easy to let one stand in for the other. How much work went into building a thing is a fact about the builder's own history with it. How well the thing actually performs is a fact about the thing. Nothing connects them automatically, a lot of careful effort can still produce something mediocre, and something thrown together fast can turn out fine, but the person who did the building is in a uniquely bad position to keep the two facts separate, because the effort is a real memory sitting right next to the finished thing every time they look at it.

That's a different claim than "people are bad judges of quality." A team can be genuinely skilled and still fall for this, because the distortion isn't about competence, it's about which fact is doing the emotional work when a decision gets made. The question "is this good" quietly gets answered by a different question, "did I work hard on this," and the two questions feel like the same question from the inside.

Where this gets its name

Behavioral economics has documented this specific distortion with more precision than a general sense that people like their own work. In 2012, Michael Norton, Daniel Mochon, and Dan Ariely published "The IKEA Effect: When Labor Leads to Love" (Journal of Consumer Psychology), running a set of studies where participants assembled IKEA storage boxes, folded origami, and built Lego sets, then valued their own creations against ones a stranger or an expert had made. Builders consistently valued their own work close to what an expert's version was worth, and expected other people to share that high opinion of it, when in fact outside observers rated the amateur creations far lower. The gap wasn't small, and it wasn't limited to people who considered themselves particularly skilled.

The paper's sharpest finding is a boundary condition, not the headline result: the effect only shows up when the labor actually finishes. In one version of the experiment, participants built something and then had it taken apart in front of them before being asked to value it, and the inflated valuation disappeared. Effort that never reaches a completed result doesn't produce the attachment. It's specifically the experience of finishing something that does it, not merely touching the parts.

The honest limit: this is a specific effect, not two other well-known ones wearing a different name

It's worth being precise about which nearby idea this is, because two other effects sit close enough to blur into it. The endowment effect, demonstrated by Daniel Kahneman, Jack Knetsch, and Richard Thaler in their 1990 paper "Experimental Tests of the Endowment Effect and the Coase Theorem" (Journal of Political Economy), showed that simply owning something, even a coffee mug handed out minutes earlier with zero effort involved, roughly doubles how much a person demands to give it up compared to what a stranger would pay for the identical mug. Norton and his coauthors explicitly ran this as a separate condition rather than treating it as included in what they measured: give someone an object to own but not to build, and the direction of the bump matched the endowment effect, though in their own data that particular gap didn't clear statistical significance. The two effects can show up together in the same object, ownership plus labor, but neither requires the other, and the IKEA effect isn't a special case of the endowment effect, it's a distinct source of extra valuation layered on top of whatever ownership alone contributes, ownership itself well established as a real effect by other research even where this particular sample was too small to confirm it on its own. Sunk cost is a different mechanism again, one that doesn't require an unfinished object or more spending on the horizon: Hal Arkes and Catherine Blumer's 1985 paper "The Psychology of Sunk Cost" (Organizational Behavior and Human Decision Processes) defines it as a greater tendency to continue an endeavor once money, effort, or time has already gone into it, which covers something as ordinary as continuing to use or maintain a tool that's long since finished. The two effects can coexist in the exact same decision, a team keeps maintaining a finished internal tool partly because building it cost real time, and partly because they're fond of the thing they made, but they're answering different questions: one is about whether to keep going given what's already sunk, the other is about how much a finished thing is worth given who made it.

None of this means self-built tools are worse, or that the feeling is baseless in every case. Sometimes the thing you built really is better for your specific situation than what you could buy. What the research rules out is treating the attachment itself as proof of that. The inflated valuation shows up whether the self-built thing is actually good or not, which is exactly what makes it a poor guide to which one is better.

Where this fits at Brief

This is the risk sitting underneath a lot of build-versus-buy decisions, including the plainest version: a team's own hacked-together tracking sheet or internal script against a product built for the exact job, like a shared product context layer instead of scattered decisions no one remembers making. The research here was about individuals valuing furniture and origami, not about which tool teams pick, so this isn't a claim that homegrown tools lose fair comparisons as a rule. What it does say is that the people deciding whether to keep a self-built tool are the same people whose valuation of it can't be trusted as a clean signal, since the same inflation shows up whether the tool is actually good or not.

Next time your team defends a tool it built in-house over one built for the job, is the defense about what the tool actually does, or about who spent the weekend building it?

Frequently asked questions

What is the IKEA effect? The tendency to place a disproportionately high value on something because of the labor invested in creating it, independent of how good the finished thing actually is. Demonstrated by Norton, Mochon, and Ariely in 2012, using furniture assembly, origami, and Lego-building experiments.

How is the IKEA effect different from the endowment effect? The endowment effect is about ownership alone, simply possessing something, with no effort involved, makes people value it more than a non-owner would, an effect well established in the wider literature. The two effects aren't nested inside each other. Norton and his coauthors tested ownership-without-building as its own separate condition and found labor produces a significant valuation gap that ownership alone, in their sample, did not, evidence that the IKEA effect is a distinct, larger source of valuation, not just ownership by another name.

Is the IKEA effect the same as sunk cost fallacy? No, and sunk cost is broader than "spending on something unfinished." Arkes and Blumer defined it as a greater tendency to continue an endeavor once money, effort, or time has already gone into it, which covers continuing to use or maintain something that's long since finished. The two can coexist in the same decision, but sunk cost is about whether to keep going given past investment, while the IKEA effect is about how much a finished thing gets valued because of the labor that made it.

Does the IKEA effect mean homemade tools are always worse than bought ones? No. Some self-built tools genuinely are the better fit for the job. What the research rules out is treating fondness for a tool as evidence either way, since the same fondness turns up regardless of how the tool actually performs.