Self Observation And Triggers

Because narcissists build themselves up from external things rather than internal things, they are constantly comparing themselves to others, and constantly TRYING to find reasons to put others down (so they can feel "above'), or trying to fit in with those who they see as "elite", which can be as simple as gender or race. Their exaggerated, dramatic reactions and judgments toward others are their way of making themselves feel important and justified. When it's someone we care for very much, it can be heart wrenching to watch them go through this, even when we are the target of their extreme put-downs. The irony is we know why they're doing it because we have the ability to empathize. They don't, which is why they're doing it. They can't watch themselves treating us with such incredible disrespect, they don't have that ability; in their minds, they are simply reacting naturally, the way anyone else would, to our words and actions. And since they can't see past their own triggers and reactions, they also can't see anything real about us, their target. They might be reacting so dramatically to something as small as a facial expression that their mother, or perhaps stepmother, used to do, or a familiar intonation that sounds like their father. But since they lack the ability to self-observe and self-reflect, they are not going to make the connection.
To use a very basic animal analogy, most people know that many dogs can't stand mail carriers or delivery people. What's up with that? To the dog, there is a human who is coming toward the house, and this human is carrying something, and wearing a certain matching outfit, every time. Some of these humans wear the outfit AND a hat... And they are DOING something on purpose, not just walking by, they have a certain stance about them. (Who knows, maybe they give off a certain pheromone because they're working that dogs can smell.) All of these factors stick in the dog's mind, the dog has learned that humans wearing certain kinds of clothing, especially if they're driving a truck, are the ones who keep COMING to the HOME, and invading the territory. These humans are not "friends", because they are not invited in and given drink and food, and warmly greeted. So they aren't welcome... like friends... but they come anyway... brazenly... regardless of the warning barks....
So the uniformed delivery human becomes a trigger for the dog. The dog just has to see them, or hear the truck, and the dog is off her or his rocker, as if this person is charging toward the house with a bayonet.
The dog does not THINK, the dog does not see that it's just a person, and it could be a very nice and kind person, who loves dogs, who is not a threat at all, who has 2 dogs at home, and children, and a spouse who also is kind and loves dogs. The dog doesn't ponder or wonder about the person, or the person's INTENT, or the person's LIFE, or PERSONALITY. The dog just sees the uniform and is instantaneously compelled to bark like a canine banshee, for no real, logical reason. Just the trigger.

This is how humans are triggered also. The brunette woman in the hall reminds Susan of the brunette girl in high school who picked on her~ her subconscious reacts with a twinge of something like avoidance and resentment, even though she's never met the woman in her life. In the office, every time Susan laughs, Mary hears her Aunt's laugh, who she loved very dearly, and she projects that onto Susan. When Mary smiles broadly, showing a lovely set of straight teeth, Andy is triggered to think of his stepmother who smiled like that, but was not kind to him. So Andy projects that onto Mary, doesn't "like" her, which is unfortunate, because Mary is actually the kindest and funniest person in the whole office. Andy is not aware that his skewed assessment of Mary is based on his association with his stepmother.

Sentient Humans?

In order to understand others, one must be able to empathize. In order to empathize, one must learn to understand others. Believing we know all about a person from some superficial external things is a human immaturity that most of us go through in childhood, and many of us don't completely outgrow. But those who have grown to a certain level of maturity, and are able to learn and grasp new information, are aware that they are not fully mature, completely wise, and a fully enlightened, omniscient being, and so can keep maturing and growing. When we ACCEPT that we are humans, and that humans have certain tendencies like making sweeping judgments with little or no information, making huge assumptions, believing our own ego b.s., and trying to dominate other humans just because we share chimpanzee DNA, we can learn how to grow out of these tendencies. Those who can't accept their own creature feature issues are funny, they'll do things like project these issues onto others and deny having them themselves; they'll have magnified domination tendencies BECAUSE of their denial, or they'll try to JUSTIFY their behavior with the excuse of "genetics"; "I can't help the way I was made". Unfortunately for them, using the excuse of "I can't help it" is forfeiting sentience. The definition of Sentience is self-awareness. With self-awareness comes awareness of others. With self-awareness comes self-observation, and the ability to control one's behavior. Creatures who are not self-aware can not control their own behavior beyond their emotional and hormonal reactions, and we don't give them "rights" because of this very reason. A person who can't "help" their own behavior apparently is not a Sentient being, and may not be safe to roam around in society without direct supervision.