There may be few more interesting things in the world than observing people.

If you see the same person several times then you can classify them according to one or more personality traits - that's right, a person can have several personalities at the same time - and you can see how they act under these circumstances.

A study of personality traits can also help you predict how a person with a certain personality will act in a particular circumstance. This can be extremely useful when trying to understand and analyze the way and why people do what they do, when they do, where they do, and according to which issues they do things.

A crowded bus, for example, is a good way to see how people act in public and to see the way different personality traits affect them. You can watch them for an extended period of time without letting them know that they are being watched.

This can also happen in a crowded room such as a wedding hall. Some people act very differently in public than in private.

Professional indicators

Those who are reading this this site are likely to know about the Myers-Briggs Type Indicator. It measures personalities based on four dichotomies: extraversion/introversion, sensing/intuition, thinking/feeling, and judging/perceiving.

A person's tendencies, or types, are indicated by combinations of four letters, such as ISTJ, for Introvert Sensing Thinking Judging, or ENFP for Extrovert INtuitive Feeling Perceiving

The developers assume that the client, rather than a test, is the best judge of his or her own preferences.

If you want a formal analysis, go for this Type Indicator. If you want to go by your own feelings, based on your subjective observations of others, then read this section in the website.