Studies of brain chemicals add further weight to this relationship. In dogs and humans (in fact all mammals) the behaviours that bond individuals are maintained through a cocktail of molecules that are absorbed in different ways by the brain. Many of these are regulated by brain hormones that include vasopressin and oxytocin, the (dramatically over-hyped) “love” molecule. In all mammals (including humans) production of this hormone spikes when individuals are sexually aroused, while giving birth and while nursing offspring. It also rises when we see those that we love, particularly close family members. Interestingly, dogs respond with an oxytocin surge not only when interacting with one another, but also (unlike nearly all other mammals) when interacting with humans.

A similar phenomenon occurs with cats. One small-scale study suggests that cats do receive an oxytocin boost upon being petted by their owners, so there may be love there, but it reflects one-fifth of the amount seen in dogs. If anything sums up cats, it’s this.