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This is Scientific American's 60-Second Science. I’m Karen Hopkin. This will just take a minute.

The first time you visit your boyfriend’s place, he no doubt tidies up, to give you the illusion that he doesn’t live like an animal. Well, animals, too, can use optical illusions to woo a mate. Take the bowerbird.

Male bowerbirds build elaborate shelters to try to attract a female. They decorate these bachelor pads with shells, bones and pebbles¹, and even lay a pathway of sticks along which the female can walk to get the best view. But that path provides more than just a welcome mat. It allows the male bird to set the stage so that the décor will accentuate——even exaggerate——his size, a typical sign of good genes².

See, male bowerbirds line their courtyards with objects arranged from smallest to largest. Viewed from the walkway, this layout makes the court seem smaller and the bird sitting at its center look larger. When scientists went in and reversed the gradient, the male bowerbirds restored it within days, results published in the journal Current Biology.

Of course, the females may be on to the trick. And rather than being fooled about size, a female may be selecting a male based on how clever he is to make himself look so swell³. Or so swelled⁴.

Thanks for the minute. For Scientific American’s 60-Second Science. I’m Karen Hopkin.