All mammals are born with at least seven Emotional Systems: SEEKING, FEAR, RAGE, LUST, CARE, PLAY, PANIC/GRIEF.*

These Emotional Systems direct how we react to the environment and different stimuli by activating certain emotional circuits. Each of these circuits is responsible for controlling and activating specific behaviors that trigger physiological changes involving the release of different hormones and neurotransmitters. "Play" is a joyful and spontaneous activity that takes the form of predatory practice through behaviors such as chasing, grabbing or biting, but in a safe and relaxed way, promoting the dog's well-being and happiness, as "playing" is an intrinsically motivating and rewarding activity. In this sense, several behaviors such as "sit," "fetch," "down," "stay," and "give" can be trained using "play" as motivation and reward. When the dog "plays" by practicing predatory behaviors, the PLAY Emotional System is activated, leading to the release of dopamine, oxytocin, and endogenous opioids, responsible for the feeling of motivation, tranquility, and well-being. This hormonal release provides a calming and anti-stress effect, making the dog feel comfortable and secure.

Training through play (PLAY) is considered the most significant activity when it comes to improving behavioral modification plans and is the central essence of the human-dog relationship. Training through "play" promotes a relaxed environment that reduces misunderstandings and communication failures between the two species. During "play," the connection between dogs and their owners is enhanced, increasing tolerance and affection. As a result, training through "play" can promote mental and physical well-being, reducing stress and anxiety. Additionally, since the dog is not stressed, they learn more efficiently as learning during social "play" generates excitement and is intrinsically rewarding. Positive interactions during these activities involving eye and physical contact provide antidepressant benefits by promoting the release of endorphins, prolactin, and oxytocin in both owners and dogs. It also stimulates neurological development through the release of other proteins in the brain that facilitate the ability to cope with stressful and conflicting situations, producing positive effects on the limbic system by increasing the functioning of the hippocampus responsible for conscious, contextual, and long-term memory.