in a "social observer's effect"? If you look at somebody, a stranger, you can see him as possibly being dangerous if you are wary of strangers in public or as as another nice soul populating your surroundings if you are naive or etc.
I think your view of other people is heavily skewed by situation and experience. Different people will see who the expect to see in a given situation, and respond accordingly. If the other person responds differently than they anticipate, their views shift accordingly.
How would you compare it to Quantum theory's "observer's effect"? Your observation produces the results of the position of the particle like when you look at somebody, the person will be a certain way to you, like if you believe him to be a scoundrel, the will appear to be a scoundrel to you. Would you agree with that, lol?
I would, also postulate that that first impression will maintain whatever predisposition you have towards that person unless they say, do and react in ways contrary to that consistently. If they don’t interact enough that initial perception will remain until such a time as something contrary happens