Hmm..I know for sure that it's a psychological fact that when human beings meet each other for the first time, the very first impressions are physical attributes; tall, short, handsome, etc.. From then on, it depends on the individual. As for me, the next impression I get depends on the attitude the guy gives me. If he gives off a nasty or self-centered attitude, I will then get the impression that that is the way he is always.
Sometimes the guy/woman might be going thru a rough day when u meet them or when u run into them so u cant always go by that.
That's why it's first impressions. It doesn't have to be true; it's the impression someone is getting of another person based on what they see/hear/whatever.