Studies have also shown that looking a dog in the eyes can boost levels of oxytocin (a hormone involved in social bonding), in both the person and the dog

If you have a special bond with an animal, you planned your relationship with them before you were born.


Dogs are the only species that, like a human child, runs to its human when it is frightened, anxious or just pleased to see us. It is also the only animal, aside from other humans, that actively seeks out eye contact with people, and truly wants to be with us. Cats too come to us when we are down and will show they are pleased to see us with a lick on the hand or a gentle purr to express their own feelings of contentment.

 
http://www.independent.co.uk/property/house-and-home/pets/why-pets-unconditionally-love-their-owners-dogs-cats-a7447406.html