Jealousy may not be an emotion unique to humans, a new study has found. Published in the journal PLOS ONE, researchers describe the first experimental test of jealousy in dogs which found that these animals displayed jealous behaviors when attention from owners was directed towards a fake pooch. This suggests that a form of this emotion exists in at least one other social species alongside humans.

While many dog owners will tell you that their canine companion gets jealous if attention is diverted away from them, given the complex cognitions thought to be involved in this emotion many have assumed that jealousy is in fact unique to humans. Some have even proposed that jealousy requires self-reflection and the ability to understand conscious intentions. However, much research into this area has primarily focused on jealousy within romantic relationships over infidelity, neglecting to investigate other forms of this emotion, especially in other species.

In recent years, opponents have argued that jealousy may not actually require complex cognitive abilities. Furthermore, it is evident that not all jealousy revolves around sex and romantic relationships given that it concerns siblings, friends and even colleagues. This suggests that jealousy may have evolved as a way to protect resources in a wide-range of relationships, hinting that it may occur in other social animals, too.

To address this gap in our knowledge, University of California San Diego researchers used a method developed to investigate jealousy in human infants to probe this emotion in dogs. They recorded the behavior of 36 dogs in their own homes as their owners ignored them and played with 3 different items: a stuffed animated dog that barked and wagged its tail, a jack-o’-lantern or a book. The owners were asked to treat the stuffed dog and the lantern as if they were dogs and to read the book out loud.

Researchers then assessed the responses of the dogs in terms of aggressiveness, attention seeking behavior and interest in the owner/object. They found that the dogs displayed significantly more jealous behaviors when the owner was playing with the fake dog compared with the other items.

All of the dogs nuzzled their owners when they were engaging with the stuffed dog and a significant number tried to get in between them or nudged the fake dog out of the way. Furthermore, 42% of the dogs snapped at the fake dog, whereas only one did so at the other 2 objects. Interestingly, 86% of the dogs sniffed the stuffed toy’s butt, indicating they believed it was a real dog. Taken together, these results suggested that the dogs viewed this toy dog as a rival.

This study supports the idea that jealousy does not necessarily require self-reflection or complex cognition. This “primordial” jealousy that exists at least in dogs may therefore have evolved as a way to secure resources such as food or social bonds and likely served as a platform for the development of complex jealousy. 

[Via Scientific American, Science and PLOS ONE]

[Header image "Diva Dog," by Lon Martin, via Flickr, used in accordance with CC BY-NC-ND 2.0]