Because adult dogs' behavior are already 'fixed' to make them suitable for domestic environments. Adult dogs are trained Most adult dogs in shelters are trained. They are housebroken and potty trained. Although there is always the possibility of bad behavior due to the history of ownership the dogs have. To make the selection easier for you, you can either choose use dog breed selectors available online or use some begin your search with the breed you have set your eyes on. You can also narrow down your choices to certain characteristics like: - breed size, - energy level, - exercise requirements, - playfulness, - affection level, - tolerance towards other dogs or pets, - ease of training, - protection ability, - grooming requirements, and - tolerance to heat and cold Dog size Dogs have a wide range of sizes. It motivates dogs to obey more readily and more eager to learn. The results of positive reinforcement are more permanent and lessen aggressive behavior. For both people and animals, chemicals are released in the brain creating pleasant associations when positive reinforcement is used. Basically, positive reinforcement is rewarding a dog whether by food, by a hug and embrace, and by play. If it learns from the start that you play dominance or is the alpha male, it would be easier to make the dog follow your commands. Dog Training Dog obedience training must start as early as possible because the dog has to learn manners and to follow commands. Excessive barking, jumping on people, quarrelling with other dogs and house pets, chewing on furniture, scratching the carpet are just some of the examples untrained dogs do that often results to embarrassment to their owners. A change in job, moving to a new location, getting married, major health concerns and limited time due to more responsibilities will only add up to the pressure where the dog is likely to suffer. - Older pets do not always welcome new pets in the house; on the contrary, older pets tend to be wary with new, younger ones. Nevertheless with senior dogs, you need not spend extra on a new couch or endure months of housebreaking. You can also enjoy the company of a calmer, less aggressive, and more tolerant pet. Senior dogs make for great pets for children and old people alike. They do not demand as much attention as their younger counterparts do and they are more skillful at human interaction.