Why we can't resist puppy dog eyes...

Dogs have evolved to exploit the bonding system that keeps lovers, and mothers and babies, together. This evolutionary behaviour has made dogs man's best friend ever since...

The 'love' hormone oxytocin is released in the brain during sexual activity and also when a baby suckles. It seems to drive strong attachment between individuals and scientists have speculated that this is the basis of mother-baby bonding and why sex keeps couples together.

Now researchers in Japan have found that, during their domestication, dogs have learned to tap into this system to make themselves part of the family and they do it by gazing at their owners.

Writing in Science, Azabu University researcher Miho Nagasawa and her colleagues compared urine oxytocin levels in a group of dogs and their owners before and after the spent time interacting with each other.

Prolonged eye contact, they found, was associated with a significant oxytocin surge in both. The experiment conducted on owners and human-reared wolves, however, did not show any such relationship.

In a follow-up experiment, the researchers administered a dose of oxytocin to the dogs via their noses then then monitored how long they spent gazing into their owner's eyes. Female dogs, they found, significantly increased their eye-contact time. The results show that both dogs and humans appear to find the process of establishing and maintaining eye contact pleasurable.

Dogs must have evolved to do this over the past 10,000 years of domestication, because the wolves tested in the study actively avoid eye contact, which they regard as an aggressive challenge.  Moreover, by staring doe-eyed at their owners, canny canines have clearly worked out that this is the way you get fed titbits under the table.