In my experience there are two types of people:
—Folks who pay attention to what is happening around them at all times. They will notice changes (positive and negative) and act accordingly.
—Folks who are blinded by their beliefs/ideology. They ignore what is happening around them when it does not fit the template. They are a danger to themselves and others.
I call those two classes sheep and wolves. I tend to watch for aware people and keep an eye on them. Wife has also picked up the skill somewhat. Skill got quite honed in Israel, most tend to be situationally aware when suicide bombers are thrown in the daily mix.
I must admit I am more lax these days since I came home. A band of ferrals are easier to spot than a Jihadi in the mix.
You can often spot other wolves, but it’s the fidgety ones that are dangerous.