The eternal dispute between dog and cat lovers will probably never end.
However, scientists have found out which out of our feline or canine friends love us more.
As part of a new BBC2 documentary called Cats v Dogs, hosted by animal experts Chris Packham and Liz Bonnin, a neuroscientist has investigated which species prefers humans.
We already knew that, like humans, dogs release the 'love hormone' oxycotin.
This test has never before been done on cats.
"We have pretty good evidence that dogs actually love their humans," according to Dr Paul Zak, who conducted the study.
"A couple of small-scale studies have shown that when owners interact with their dogs, the human and their dog appear to release oxytocin.
"It's one of the chemical measures of love in mammals. Humans produce the hormone in our brains when we care about someone. For example, when we see our spouse or child the levels in our bloodstream typically rise by 40 to 60 per cent."
The neuroscientist checked the oxycotin levels in both cats and dogs after playing with their owners.
He took saliva samples from 10 cats and 10 dogs on two occasions - 10 minutes before a playtime session with their owners and immediately after - and tested both samples for oxytocin.
The results show the hormone increased by an average of 57.2 per cent in dogs but only by 12 per cent in cats.
This means in theory, dogs love their humans more than cats do.
"I was really surprised to discover that dogs produced such high levels of oxytocin… the dog level of 57.2 per cent is a very powerful response. It shows these dogs really care about their owners. It was also a nice surprise to discover that cats produce any at all. At least some of the time, cats seem to bond with their owners," he added.
Some think that cats don't actually like their owners at all - this study at least proves that wrong.
Cats beat out dogs in one area, however - they are better at surviving.
A study of 2,000 fossils has revealed that the felids are much better at surviving than canids.
A team of scientists found that cats have played a significant role in making 40 dog species extinct.
Cats often out-competed dogs for food rations because they are generally more effective hunters.
No evidence has been found that dogs have ever wiped out a cat species.
The dog family - which includes wolves from which our domesticated dogs descend - originated in North America 40 million years ago.
20 million years later there were more than 30 species of dog on the continent. Then the cat family arrived and caused a period of dramatic decline among the dog family.
The Telegraph, London
