MARY LOUISE KELLY, HOST:
Now to cats. If you've spent time around them, you likely know they love to curl up in small, cozy boxes. What you may not know - if you draw a square shape on the floor, cats will often sit in that, too. As NPR's Nell Greenfieldboyce reports, this made scientists curious about how cats would react to a certain optical illusion.
NELL GREENFIELDBOYCE, BYLINE: No one knows why cats love to get in boxes. Gabriella Smith is an animal behavior researcher with the Alex Foundation. She says one theory is that cats are comforted by pressure on their sides because it reminds them of when they were kittens, sleeping with littermates.
GABRIELLA SMITH: Another theory is that since they're ambush predators, they have attraction to hiding.
GREENFIELDBOYCE: But neither of those reasons explains why cats will also go sit inside a two-dimensional square. Smith recently wondered if cats would sit inside the optical illusion of a square. There's a famous one, the Kanizsa illusion.
SMITH: The Kanizsa Illusion can be described as four Pac-Men with the right angle facing inwards. So the four Pac-Man mouths face inwards, and they create an illusory square.
GREENFIELDBOYCE: She designed an experiment that people could do at home with their cats by downloading a packet of information that included different shapes.
SMITH: They printed them out, cut them out, taped them on the floor, and then took out their phone and recorded their cat for five minutes interacting with the stimuli.
GREENFIELDBOYCE: The cats got to ponder three different choices - the outline of a square, four Pac-Men set up to create the Kanizsa illusion and four Pac-Men that faced the wrong way. The cats liked the square, and they liked the illusion of the square, too.
SMITH: Cats stood or sat within the contours of the Kanizsa illusion just as much as the square.
GREENFIELDBOYCE: She and her colleagues describe their work in the journal Applied Animal Behaviour Science. And it got the attention of Kristyn Vitale. She's a cat behavior researcher with Unity College.
KRISTYN VITALE: I did think what was really interesting about it was the methods that they used to collect the data, which was that citizen science approach.
GREENFIELDBOYCE: She thinks cat owners collecting data at home has a lot of promise for future research on cat behavior and cognition. Cats have historically been harder to study than dogs. Cats generally don't like trips to strange places like a lab, and cooperation is not really their thing.
Nell Greenfieldboyce, NPR News.
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