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20/07/2016, 12:00

'Love hormone' that secures bond between a woman and her newborn baby also occurs with dogs and their owners, say scientists

Oxytocin, the hormone released into the bloodstream by women after childbirth, also increases in both dogs and their owners when interacting

The “love hormone” that secures the bond between a woman and her newborn baby is also involved in bonding between dogs and their owners, scientists have found.

Researchers in Japan have found that oxytocin, the hormone released into the bloodstream by women after childbirth and babies during breast-feeding, also increases in both dogs and their owners after they interact with each other.

The scientists showed it was possible to increase the number of times that female dogs gazed at their owners by spraying the dogs’ noses with oxytocin, suggesting a direct link between the hormone and bonding behaviour between dogs and humans.

They also found that increased gazing by a dog towards its owner led to an increase in oxytocin in the dog owner’s bloodstream, indicating a direct feedback between oxytocin levels in a dog and those in its owner, the researchers said.

The findings, published in the journal Science, suggest a possible physiological mechanism that allowed some wolves living near Stone Age human settlements thousands of years ago to eventually evolve into tame, domesticated pets the scientists said.

The study, led by Takefumi Kikusui of Azabu University in Sagamihara, also involved experiments with wolf cubs reared by hand. These failed to find a similar relationship between oxytocin levels in their human keepers and the wolves – suggesting that oxytocin levels in dogs and humans co-evolved after the first wolves started to become domesticated.

Since wolf cubs raised by hand do not show the same response as domesticated dogs, it is likely that oxytocin was a critical factor that allowed dogs and humans to live together and interact to closely, scientists said.

“Evolution is notoriously thrifty, often recycling old mechanisms for new purposes,” say animal behaviourists Evan MacLean and Brian Hare in an accompanying editorial in Science.

“The findings suggest that dogs have taken advantage of our parental sensitivities – using behaviours such as staring into our eyes – to generate feelings of social reward and caretaking behaviour,” they say.

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