I've been doing a little social experiment for the past few months, so I will share my results here.
I often go walking about in my neighborhood, and when walking, I would encounter other people walking. Every time I saw someone, I would either say hello to them or wait for them to say hello to me. 50/50. I walked in a completely natural manner for me. I do not have an unusual gait, and I do not look unusual in any way.
The result of the experiment was that if I did not say hello to the other person, then the other person did not say hello to me. No one voluntarily greeted me. Not a single time. There were hundreds of encounters, and not a single time did someone say hello to me if I did not say hello to them first. They always responded when I initiated.
I also tried modulating my body language and facial expressions, such as by turning myself slightly towards their direction or looking up and opening up my face from neutral to friendly, but none of these modulations had any effect whatsoever. However, when I walked with my NT mother, people often said hello to her before she said hello to them. I don't know what signals I am sending when I am walking alone, but I must have appeared 1) hostile, 2) lost in my own world, 3) 4) 5) 6) 7) ???, such that no one said hello to me.
Just wanted to share this experiment for funsies.
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Drain and plane and grain and blain your brain, and then again,
Propane and butane out of the gas main, your blain shall sustain!