We misjudge people easily. Because when we feel good about ourselves we expect people to be in our mirror image. And when we have low self-esteem we appreciate people who have opposite qualities as ourselves. Our external perception is based on the internal perception we have for ourselves. This is the cause of error in judgement. The error comes because it is highly possible that you are feeling good about yourself, and people around you have an inverted image of you. This causes the theory to be thrown for a toss.
People operate in different gears. Some are calm, collected, and composed. Others are perceptually happy, hurried, and hyperactive. The 1st type we call as operating in the 1st gear. That's the way a car is in its 1st gear, slow and steady. The 2nd type we term as moving in the 4th gear - at a high speed, with more fun, and risk. More deadly accidents happen only in 4th gear. But the thrill is also greater. Just as a car operates in different gears, so do people. Same people operate in different gears at different times and sometimes the same people operate in the same gear all the time.
We are unable to quickly judge another person with depth. So we have to rely on superficial methods. One of the most time-tested method even though it is purely superficial is the way of judging another person's character, and worth through the gear which he operates. Some people rate a 1st gear person highly and some rate a 4th gear person highly. The mistake here is very simple. It never matters which gear you operate, it matters at what depth and intensity in each gear you operate. The depth and intensity can never be ascertained through a short cut method as above. It needs deep understanding and many interactions to know. Hence, depth matters, the gear does not matter.