Domesticated animals often show signs of pleasure and relaxation when being rubbed, massaged or otherwise petted by people. Now researchers think they know why. The research also suggests how owners might best show affection to their pets. The secret is to think like the animal. A team of French and Austrian scientists found that cows relax, to the point that their heart rate lowers, when petted in body regions they often target when grooming each other. They believe the findings could also apply to cats, dogs, farm animals and even rats.