Although scientists have some understanding of social recognition and where it takes place in the brain, we still don't entirely understand how it happens. The missing link could be oxytocin, the so-called "hug", "love" or "cuddle" hormone. Oxytocin has a key role in both childbirth, lactation and sperm movement, but it also has an increasingly recognised role in our social behaviour, acting as a chemical messenger in pathways that control sexual arousal, recognition, trust, mother-infant and human-pet bonding.
Oxytocin works in tandem with another brain hormone, vasopressin, to help to modulate our response to stress and deal with social situations. Unsurprisingly, there's a lot of interest in a possible role for oxytocin in addiction, brain injury, anorexia, depression, autism and severe anxiety.
And there are other reasons that pets and therapy animals are increasingly recognised as being good for our mental health. In addition to helping to alleviate stress, anxiety, depression and loneliness, there are all the benefits that come from having to exercise a dog. Daily walks outdoors boost physical and emotional wellbeing. Chucking sticks, picking up balls - even scooping up dog poo - can provide an all-round workout. Increasingly that knowledge is being turned to practical use, with some lovely effects. When the Centre for Mental Health ran an evaluation on therapy dogs in prisons, for example, the feedback was off the scale. "I don't know what it is, but even when I am running around with [the dog] I just feel better inside, calmer, more peaceful," said one prisoner. Another told the interviewer: "Dogs have a magic effect on you, you can feel their love and that just makes you feel better inside you." The good feelings persist even after the dogs have left, the reviewers found, with one subject saying: "I just walk around for the rest of the day on cloud nine."