Who doesn’t love puppies? Experts consider puppyhood, particularly the first three to four months, the most important period of a dog’s life. In that short window, a dog’s experiences shape his opinions about what’s safe and what’s scary — opinions that can be hard to change later on.

Dog behavior is the internally coordinated responses of individuals or groups of domestic dogs to internal and external stimuli. It has been shaped by millennia of contact with humans and their lifestyles. As a result of this physical and social evolution, dogs, more than any other species, have acquired the ability to understand and communicate with humans and they are uniquely attuned to their behaviors. Behavioral scientists have uncovered a wide range of social-cognitive abilities in the domestic dog.

Dog intelligence is the ability of the dog to perceive information and retain it as knowledge for applying to solve problems. Dogs have been shown to learn by inference. A study with Rico showed that he knew the labels of over 200 different items. He inferred the names of novel items by exclusion learning and correctly retrieved those novel items immediately and also 4 weeks after the initial exposure. Dogs have advanced memory skills. A study documented the learning and memory capabilities of a border collie, "Chaser", who had learned the names and could associate by verbal command over 1,000 words. Dogs are able to read and react appropriately to human body language such as gesturing and pointing, and to understand human voice commands. After undergoing training to solve a simple manipulation task, dogs that are faced with an insolvable version of the same problem look at the human, while socialized wolves do not. Dogs demonstrate a theory of mind by engaging in deception.

Play 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. Dogs walked together with opportunities to play with one another, play with their owners with the same frequency as dogs being walked alone. Dogs in households with two or more dogs play more often with their owners than dogs in households with a single dog, indicating the motivation to play with other dogs does not substitute for the motivation to play with humans.[12]

It is a common misconception that winning and losing games such as "tug-of-war" and "rough-and-tumble" can influence a dog's dominance relationship with humans.