Harley feel very happy when had a quite time playing with his ball. Playing between dogs usually involves several behaviours that are often seen in aggressive encounters, for example, nipping, biting and growling. It is therefore important for the dogs to place these behaviours in the context of play, rather than aggression. Dogs signal their intent to play with a range of behaviours including a "play-bow", "face-pawed" "open-mouthed play face" and postures inviting the other dog to chase the initiator. Similar signals are given throughout the play bout to maintain the context of the potentially aggressive activities.
From a young age, dogs engage in play with one another. Dog play is made up primarily of mock fights. It is believed that this behavior, which is most common in puppies, is training for important behaviors later in life. Play between puppies is not necessarily a 50:50 symmetry of dominant and submissive roles between the individuals; dogs who engage in greater rates of dominant behaviours (e.g. chasing, forcing partners down) at later ages also initiate play at higher rates. This could imply that winning during play becomes more important as puppies mature.
Emotional contagion is linked to facial mimicry in humans and primates. Facial mimicry is an automatic response that occurs in less than 1 second in which one person involuntary mimics another person's facial expressions, forming empathy. It has also been found in dogs at play, and play sessions lasted longer when there were facial mimicry signals from one dog to another.
The motivation for a dog to play with another dog is distinct from that of a dog playing with a human.