When it comes to caring for a dog, most owners would do anything to ensure their four-legged friend is happy and healthy.
But they might not realise how their actions have been negatively impacting their precious pet.
A study from the University of Auckland, published in Phycological Science, has discovered even something as simple as showing affection to another animal can spark jealously in their dog.
Researchers have been investigating whether dogs can experience feelings of jealousy by tricking them into thinking their owner has been interacting with another animal behind their back.
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The team studied how 18 dogs reacted when watching their owner interact with a realistic-looking toy dog, and again when hearing their owner interact with the toy while their view was blocked.
The dogs also had to respond to a social interaction between their owner and a fleece cylinder. The toy dog served as a potential rival while the cylinder served as a control.
The study states: "Our results suggest that dogs showed jealous behaviour rather than envious behaviour.
"These findings also suggest that dogs may display more than a form of proto-jealousy, as has been suggested in the past.
"In our study, dogs selectively displayed jealous behaviour in response to a hidden social interaction rather than one that was directly observed.
"Although previous research has shown that dogs are capable of mentally representing hidden objects, this ability has never been extended to mental representations of jealousy-inducing social interactions.
"In fact, this human signature of jealousy has, to date, been demonstrated only in adult humans and has been claimed to be unique to our species.
"Dogs’ ability to 'connect the dots' and infer that their owners’ actions were directed toward a hidden rival suggests that dogs not only are capable of mentally representing social interactions but also specifically do so when interpreting interactions that might threaten the social bond they have with their owners."
The team believe this discovery has "implications above and beyond the similarities between jealous behaviour in dogs and jealousy in adult humans."
The study continues: "Our study provides evidence that dogs can mentally represent social interactions, which in itself is a complex cognitive ability.
"This finding therefore raises the question of how widely dogs might use mental representation when thinking about the world around them."
Concluding their research, the team state dogs may feel their bond with their owner is being threatened when their owner interacts with other dogs.
"These results suggest that dogs may live much richer inner lives than we often give them credit for because they add strong support for the growing evidence that dogs may experience a secondary emotion," the study adds.
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