My best friend from childhood had two beautiful dogs, a German shepherd named Sari and an Australian shepherd named Chloe. Living on a large pasture in the Midwestern countryside, the dogs were both mellow and incredibly well-behaved... that is, until my friend and I decided to mess with them. No, we didn't engage in dog shaming (see photo above); instead, we did something much more ruthless.

Sari, the German shepherd, had a bit of a jealous side. Even if she had been petted first, Sari had a strict zero tolerance policy toward affection for Chloe. She simply could not tolerate bearing witness to Chloe being petted. If she saw it, she would try to wedge herself into the situation and steal attention from Chloe. Realizing the mischief we could make, my friend and I would simultaneously pet Chloe -- complete with ostentatious adulation -- causing Sari to go ballistic. She would whine and bark and bite at Chloe. On at least one occasion, we instigated a fight.

Cruel? Yes. But, little did we know that, scientifically, we were way ahead of our time. A new study in PLoS ONE has confirmed the existence of jealousy in dogs. And the authors' methods were frighteningly similar to ours.

The team recruited 36 dogs and their owners. The owners were told to ignore their own dog while they (1) played with a stuffed toy dog that barked and wagged its tail; (2) played with a jack-o-lantern as if it were a dog; and (3) read aloud from a children's book. Conditions #2 and #3 served as controls. Condition #2 determined if simply showing affection to anything other than the dog elicited a jealous response; Condition #3 examined if ignoring the dog caused jealousy. The dogs were videotaped, and their behavior was assessed:

As shown in the figure, the dogs had a real problem with the toy dog. They were likelier to snap, touch their owner, push the object, and whine if their owner was playing with the toy dog than if he was playing with the jack-o-lantern or reading from a book. Jealous much?

It is, of course, possible that dogs are simply disturbed by toys that look like dogs -- a sort of "uncanny valley" for canines. But, 86% of the dogs sniffed the toy's butt, indicating that they were at least temporarily fooled into believing the toy was a real dog. The other 14% that did not sniff the toy's rear exhibited fewer jealous behaviors. The authors suggest that these dogs were either super intelligent (because they knew the toy was fake) or super dumb (because they did not have enough sense to recognize the toy depicted a dog).

At the very least, 86% of you dog owners have a new way to torment your pooch. But, making your dog jealous isn't very nice, so I don't recommend it.

Source: Harris CR, Prouvost C. (2014) "Jealousy in Dogs." PLoS ONE 9(7): e94597. doi:10.1371/journal.pone.0094597

(AP Photo)