Pets may be after more than affection

Your tabby cat may seem to be your best friend when she responds to a gentle pat with what seems like unconditional love and devotion.

But beware: your pet may be manipulating you into treating it like a favoured child, at the potential expense of your own offspring.

In Darwinian terms, this is highly beneficial for Rover but not such good news for the evolution of the human race, the British Psychological Society annual conference heard yesterday.

"Pet-keeping is best viewed as a form of social parasitism where one species manipulates the behaviour of the other to obtain a benefit," according to Professor John Archer of the University of Central Lancashire.

Cats and dogs can become "cuckoos in the nest" by diverting attention away from human friends, he said. They can even make it difficult for you to form relationships.

"In evolutionary terms, pet ownership is a puzzling form of behaviour since it entails provisioning another species in return for which there are no apparent benefits."

He put forward an alternative Darwinian explanation in which pets con humans with responses that have traditionally assisted human relationships.

King Charles spaniels and Chihuahuas, for instance, are particularly attractive to us because we associate their features - big eyes and chubby cheeks - with babies.

"We are able to feel in part that we are responding in the way we would respond to babies," said Professor Archer.

Owners also talk to their pets in baby talk normally reserved for young children.

Coupled with that, pets show affection in a non-judgmental way which we find attractive.