Many people have had taken a Myers-Briggs Type Indicator (MBTI) or Jung style of psychological test. What you get back is a 4 letter category such as ENTJ, which is supposed to be an assessment of how you perceive the world and how you like to make decisions.
http://en.wikipedia.org/wiki/Myers-Briggs_Type_Indicator

Here is a free one you can try: http://www.humanmetrics.com/cgi-win/JTypes2.asp.

But it appears there is more to the story.

David Keirsey takes a slightly different slant. He groups people based on just the two middle letters and calls this the Keirsey Temperament Sorter. The result is just 4 groups which he calls Guardians (ST), Idealists (NF), Artisans (SF) and Rationals (NT). You can read all about it here.
http://keirsey.com/handler.aspx?s=keirsey&f=fourtemps&tab=5&c=overview

My interest is in the group called Rationals (NT), of which I am one. Keirsey gives Einstein, Disney, Eisenhower and Gates as example. They comprise a little less than 10% of the population. My interest was really piqued when I found that not only am I an NT, but my entire family is also NT. I started asking people I know and discovered that a high proportion of them too are also NT, far more than 10%. Then I conducted a small survey amongst Mensa members, with the result that about 2/3 of them are NT as well. A further informal study amongst engineers and technology people at a conference turned up nearly 100% NT. This seems to be very significant.

I am coming to the conclusion that being Rational (and smart, which often seems to go together) gives you excellent tools to deal with the physical world, but leaves you surrounded by 90% of the population who are non-smart or non-rational or both. Perhaps the reason that Rationals are so perplexed by the behaviour of people around them is that they expect everyone else to be a Rational too, and this is clearly not the case.

So if you are a Rational, this may provide some kind of a rational explanation of why other people seem so strange. If you are not then there is a good chance you really don’t care and probably didn’t read down to here anyway.