several reasons why the dominance model is a poor choice for dog training. First, a relationship based on dominance is established to gain priority access to scarce resources, not to impose particular behaviors on the less dominant animal, so the dominance model is irrelevant for most of the behaviors that people want from their dogs, such as coming when called or walking calmly on a leash. Second dominance-submission relationships, once established, are constantly tested and must be regularly reinforced. Thus people, particularly children and the elderly, may not be able to retain their rank and are at risk of being injured if they attempt to do so. Third, dominant individuals gain priority access to resources, but only while they are present, establishing dominance over a dog does not guarantee its behavior when the dominant individual is distant or absent. Some modern-day dog trainers and researchers have argued that dominance does exist in dogs and to deny it is motivated by political correctness. Patricia McConnell wrote in her book The Other End of the Leash, "In some training and behavioral circles, all talk of dominance is classed as politically incorrect, and that these people are ardently opposed to anyone using the word in the context of dogs". Portuguese author on the behavior of animals Roger Abrantes argues the reasons that many people have difficulty comprehending the theory of dominance are because the term is poorly defined and political correctness. Colin Tennant, who is the chairman of the Canine and Feline Behaviour Association, said: "It is political correctness. If you treat a dog like a human it will treat you like a dog". Psychologist and dog trainer Stanley Coren in the 2001 book How to Speak Dog wrote, "You are the alpha dog ... You must communicate that you are the pack leader and dominant". Mexican-American dog trainer Cesar Millan wrote that, "It's essential that the humans be Pack Leaders, with the dog following. If a dog does not have strong pack leadership from its humans, it may become unbalanced, which can lead to confusion, anxiety, or aggression and behavior problems in the dog". Relationship-based training Derived from the theories of symbolic interactionism, relationship based training exploits the patterns of communication, interpretation and adjustment between dogs and their trainers. Building on a positive relationship between them, the method sets out to achieve results that benefit both the dog and the trainer, while