You love that shelf because you built it

In 2011, researchers from Harvard and Duke had volunteers assemble IKEA boxes and fold origami figures. Then they asked how much they'd pay to keep them — and people priced their own creations far above identical ones assembled by others. Their crooked origami seemed almost as valuable as an expert's.

They called it the "IKEA effect": your own effort inflates the value of what you build. You don't love the furniture despite sweating over the instructions; you love it precisely because of that.

There's fine print: the effect only shows up if you finish the job. Projects abandoned halfway generate no affection, only frustration.

Next time someone passionately defends their wobbly bookshelf, their sunken cake or their impossible side project, you'll know what's really going on: they're not defending the object. They're defending their hours.