If you share a home with a cat, you know cardboard boxes are their idea of IKEA furniture. Regardless of the size of the cat or the size of the box, furry occupants are content to idle for hours inside packing material.

Now, cutting-edge cat science has revealed cats are even obsessed with imaginary boxes.

In a new study published in Applied Animal Behavior Science, animal cognition researchers including co-author Gabriella Smith of Hunter College worked with pet owners to have them set up an optical illusion: each “corner” had a circle made of paper with a 90-degree angle cut into it. Together, the impression of a square shape on the floor was created, known as a Kanizsa square.

To make sure the cat was identifying a square as a square, the shapes were also used to create a regular square and a lopsided square. Then the cats were ushered into living areas and filmed to gauge their reaction to what they saw on the floor over a period of six days. Of the 30 cats who completed the experiment to the researchers’ satisfaction, nine regularly sat in either one of the Kanizsa or regular squares. One chose the irregular square.

What does this indicate? Because the participating cats chose to sit inside the shapes, they seem to have a strong preference for positioning themselves inside squares, or a space with boundaries similar to a box. Because they appeared comfortable inside the Kanizsa box, it also indicates cats can perceive visual illusions.

Cats may enjoy confined spaces like boxes, sinks, or even the appearance of a square because it may make them feel secure in a womb-like environment. It also helps them retain body heat. (Assuming, of course, they’re in an actual box.)

The experiment also suggests cats really don’t care about science. The initial study involved over 500 cats, with only a fraction able to be tracked throughout the entire six-day experiment.

[h/t Smithsonian]