There’s some surprising science behind why you feel so attached to your dog. Researchers at Azabu University in Japan discovered that the hormone oxytocin is produced in both dogs and people when a dog and its owner look each other in the eye. Oxytocin, known as the love hormone, strengthens maternal bonding and emotional connection.
Dogs have adapted a bonding mechanism to allow them to coexist with humans. Similarly, humans have likely evolved in some way that allows them to not just tolerate, but enjoy, other species.
For dogs, a a longer gaze creates a stronger bond. This might explain why some people feel more connected to their dog than to other people, and gives some weight to identifying dogs as “man’s best friend!”
Note: gazing will not signal friendship for all canine species. A wolf, for example, will perceive a long gaze as a threat.
Source:
http://mic.com/articles/115768/science-has-figured-out-why-looking-into-your-dog-s-eyes-is-like-falling-in-love