There is some components of human body language or movement patterns that dogs might perceive as provocations. If you unknowingly display thoses around dogs, it might unsettle them, Chronos.
Two such components come to my mind right now. The first one is eye contact. If you are one of those people who have been drilled to make eye contact or if you just think dogs' eyes are pretty in general and like to look at them (like it happens to me much of the time), you might spend more time meeting the dog's eyes then it is comfortable with. Prolonged eye contact is used by dogs to determine dominance. The less dominant dog will usually avert its eyes. If you maintain eye contact with dogs for too long, this might be perceived as a provocation. Looking at the nose or the spot between the dog's eyes will not usually trigger this reaction, so that's a way to read the dog's face without putting it off.
The other thing is the gait. Many people on the spectrum seem to have a somewhat unusual way of walking. When two dogs are preparing for a fight, they try to appear as big as possible (e.g. by raising their hackles) and they walk around each other on stiff legs. A dog threatening another dog will also approach it in a stiff-legged way. So if you tend to walk on stiffer legs than most other people, dogs might perceive that as a provocation and start to defend themselves by being loud around you. A simple way to test this theory would be to stop and to bend your knees a bit. If the dog's reaction to you changes, it was probably annoyed by your gait.
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