I frequently work with fearful or aggressive dogs. They are grouped into the same category because aggression always has a fear component unless an animal is hunting for food. Fear aggression manifests itself in warnings to tell the other dog or person to stay away. A bite is a more intense warning if the other warnings, such as growling, go unheeded.
Some dogs are uncomfortable around all people, but others will be much less reactive around certain people. My clients often want to know why this happens. On Friday I was working with a reactive female Shepherd mix named Meadow for the third time. I was hired to help her overcome her fear towards guests in the house (especially men) as well as her tendency to bark at outside noises. The first session Meadow exhibited the classic fear aggression signals of a stiff body, lowered head, wide eyes, moving her head back and forth while barking at me. As is often the case, the going was slow the first session and she barked periodically throughout the session. As instructed, my client gently moved her away to a more comfortable location each time she barked.
Meadow is fortunate to have a fantastic guardian that put the time in practicing the recommended exercises, keeping her under stress-threshold and managing her movements by keeping her away from the noises when she was not home. My goal when working with my clients is to make sure they realize that it is important to keep their dog under stress-threshold the entire time. This is not always possible, but it is the goal. If a fear-aggressive dog barks at a person, is quiet, barks again when the person moves and then quiets down again, the treatment will take a lot longer than if the dog is quiet and calm the entire session. If a dog rehearses the anxiety than it will happen more easily. One way to think about it is that it makes the dog more reactive or "jumpy" and she is just waiting until the next moment when her brain tells her she needs to bark again.
The third session is when all the hard work paid off. Meadow was much more comfortable with me and even came to me and allowed me to pet her and she leaned into me like we were old friends. While I was petting Meadow, my client mentioned that Meadow is fine with her daughter's fiancee, but reacts strongly to another male friend of hers even though she has met him more than five times.
I asked my client if her daughter's friend was scared of dogs and she said, "yes". This is often the reason that dogs are uncomfortable with certain people. If a dog is not completely confident with people (as is the case with Meadow) and the person shows the universal signs of stiffness, slow and unsteady movements, or wide eyes, this provides the dog with a reason to be cautious. If one animal is nervous this might lead to aggression, since fear and aggression are related. Once a dog indentifies that a person is uncomfortable, she has to be more alert that this person might be a danger to her or her family.
Another reason dogs might be uncomfortable is lack of socialization towards a certain race, body type, sex, or other distinguising characteristic such as facial hair, hair length, or clothing type. Some dogs are fine with a person until they put a baseball hat on and the dog goes ballistic. In my client's case, both of the men were white males about the same age and body type, so I ruled out socialization. It most likely was the difference in comfort level exhibited by the two men.