When presented with a simple tray of food and a food puzzle that requires a little work to get at the yums inside, every animal ever tested has opted for the latter.

Except cats.

Rhesus monkeys, rats, chickens, bears, starlings, gerbils, chimpanzees and a wide range of other animals are drawn to food puzzles, perhaps because the food tastes sweeter to them if they’ve had to work for it, or maybe because it’s just something amusing to do.

“There is an entire body of research that shows that most species including birds, rodents, wolves, primates – even giraffes – prefer to work for their food,” said Mikel Delgado, a cat behaviorist and lead author of the newest study on the phenomenon known as contrafreeloading. “What’s surprising is out of all these species cats seem to be the only ones that showed no strong tendency to contrafreeload.”

Delgado, a research affiliate at UC Davis’ School of Veterinary Medicine, used a clear puzzle feeder so the cats in her study could see the treats inside. A few feline study participants gave it a shot, but only after grabbing themselves some easy grub first. Other cats just ignored the food puzzle and munched exclusively from the tray.

While this is at least the second study to specifically test whether cats “freeload” their meals, the why of this particular feline behavior remains a mystery. Delgado cautioned against the obvious conclusion — that cats are just lazy — and pointed out that several cats in the study were active and expending energy, just not with the puzzle feeder.

One possible explanation: As hunters and obligate carnivores, cats simply may not enjoy games that simulate foraging the way omnivores and herbivores do.

The study was published on July 26 in the academic journal Animal Cognition. Read it here.