They have long been known as man’s best friend: loyal companions that adore their owners.
But it’s not just an act to make sure they get fed – dogs really are capable of love, research has shown.
Scientists at the Claremont Graduate University in California found that domesticated animals release oxytocin in intimate situations, The Atlantic reported.
Known as the “love hormone”, it is the same chemical used to create close bonds between humans.
Professor Paul Zak and his lab carried out a number of experiments to measure the levels of oxytocin released when pets interacted with both other animals and humans.
Zak travelled to an animal refugee in Arkansas where different species interact with one another regularly. While there, Zak obtained blood samples from a domestic mixed-breed terrier and a goat that often played together.
Their play involved “chasing each other, jumping towards each other, and engaging in simulated fighting (baring teeth and snarling)”.
The two young males were placed together in an enclosure where they engaged in play for 15 minutes, after which another blood sample was taken.
“We found that the dog had a 48 per cent increase in oxytocin. This shows that the dog was quite attached to the goat. The moderate change in oxytocin suggests the dog viewed the goat as a ‘friend’,” Zak said.
“More striking was the goat's reaction to the dog: It had a 210 per cent increase in oxytocin. At that level of increase, within the framework of oxytocin as the ‘love hormone’, we essentially found that the goat might have been in love with the dog.”
He added: “The only time I have seen such a surge in oxytocin in humans is when someone sees their loved one, is romantically attracted to someone, or is shown an enormous kindness.”
Zak said that the results suggested that pets may feel love for their owners.
He said: “That animals of different species induce oxytocin release in each other suggests that they, like us, may be capable of love. It is quite possible that Fido and Boots may feel the same way about you as you do about them. You can even call it love.”
And it works the other way around too. Owners that love their pets experience a surge in oxytocin when spending time with their favourite pooch or moggy - but not everyone is a pet person.
In another experiment the researchers obtained blood samples from 100 participants, who then went into a private room and played with a dog or cat for 15 minutes.
Following this, a second blood sample was taken and levels of oxytocin were measured.
The results showed that only 30 per cent of the participants experienced increased levels of oxytocin after interacting with the animals.
Zak said that people who had owned dogs in the past were more likely to feel a bond while playing with the animals than those who had owned cats, or those who had never owned pets at all.
He said: “Dogs are simply more 'people-oriented' than cats, and previous pet ownership seems to have trained our brains to bond with them.”