In the wild, good judgment about what to trust and what to avoid is vital for survival. Wolves, for example, generally opt to avoid conflict rather than risk injury. Dogs, descendants of wolves, have the same instincts as their wild brethren. Whether they can use these instincts to judge humans, however, is debated.
Dogs view the world almost entirely by smell. In fact, smell is a dog’s primary sense. This is why a mop-topped sheepdog can still navigate the world around him with fur covering his eyes. Thanks to their heightened sense of smell, dogs can pick up a number of cues from human beings. They can sense fear, anxiety, happiness and other emotions all by reading human scents.
Dogs are intelligent creatures, to be sure, but they generally look to their owners for information on how to react or behave. For instance, complaints about dogs not liking certain genders or certain races trace back to the anxieties of the owner rather than the dog; the dog is just reading these changes in behavior from the owner and reacting accordingly.
Behavioral cues in humans, both strangers and familiars, have a big effect on the behavior of dogs. People who act in a manner the dog is used to may make the dog feel calm, while people who act different might make the dog feel uneasy. In some cases, a dog can read a person’s behavior and demonstrate guarding behaviors that indicate distress or concern. Whether or not the dog is able to interpret character from a human's behavior is unknown but debated. A dog may act defensive in the presence of a man you're wary of, or the dog may just appear to. On the other hand, it is not unheard of for a dog to bark at someone on crutches if he has never seen a person like that before, though crutches do not say much about a person’s character.
Determining whether a person has good character is difficult for humans. There are many different ways to view character and human behavior. The same can be said for dogs; they can read common behaviors, sense anxiety and fear, and analyze the people they meet in relation to what they know, but their reactions are not necessarily based on whether that person is good or bad. They may more depend on changes they sense in you in the presence of certain individuals.
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