Our personality is intrinsic. Yes, experience can change us but at our base we stay the same. Our core is the same as it was when we were small children, formed in very early childhood. Personality typing offers a broad overview of one's personality that can be surprisingly helpful in dealing with them.
Of course, most people think of Myers- Briggs when they think of personality tests. This is my favorite personality test, of course, because it is the most specific. And, to be honest, they should. I don't know about most people but that test was spot-on when it came to me and members of my family. My sister is an ESFJ, my mother an ISTJ, my dad is an ISFJ and I, of course, am an INFP. It has not only explained us and how we think and our family dynamics.
There are other types of personality tests, of course, and I tend not to like them because they aren't as specific. I match Type 4 the most on the Enneagram test and I am a Type C. The Big Five, which is more scientifically founded, is a bit more complicated measuring how open, conscientious, extroverted, agreeable and neurotic one is.
I find this all extremely fascinating. Of course, personality tests can't be taken too seriously. Obviously, there are more than sixteen types of people in the world. But, still, I see this as a broad overview of one's personality, a basic sketch. We all have different experiences and environments and I'm sure this affects us in different ways. One ISFP, for example, might cower back in a corner at parties and the other ISFP might be jumping right into the crowd making awkward attempts to blend in with all of the extroverts. The one might be seen as shy and the other social but, at the end of the day, they both need to seriously unwind and get away from all of those people. But, at their core, they are very similar. For this reason, it might help if this is seen in conjunction with other personality test types.
Knowing one's personality type and others' personality type might help gain insight into reasoning behind their behavior as well as one's own. Why am I so freaking passionate? I'm naturally an idealist. Sure, I might have anxiety issues but, overall, I work pretty freaking hard to be laidback most of the time. Why do I feel so alone so often? I'm the rarest personality type and I'm also, well, pretty intense. I work very hard to make sure that I'm living the right way and that my values are correct and, then, if deciding that they are, work very hard to defend them. Why is my sister so manipulative and cruel sometimes, especially to those she loves the most? Well, it's a complicated question, sure, but her personality type gives some answers. She takes her value system from those she currently hangs around, making them somewhat shady. She is not intentionally malicious and she truly thinks she is being helpful and doing the right thing when she is so controlling. She wants to control her environment and depends on security and rules to keep her afloat and those include social rules; she also wants to please people and do nothing to compromise their opinion of her. Thus, having a non-conformist sister does not bode well for her although I know that she certainly has tried very hard to love and accept me. Again, personality types don't say everything but they certainly say a lot.
In addition to real life application, personality tests can be extremely helpful to a writer also. Classifying one's characters helps to understand them better and also helps enrich their personality within a story. Questionnaires are all well and good but personality tests target their cores. One of my favorite characters, Harry is an ENFP while another is an ISFP. I find this all completely interesting. Like I said, a writer can't rely on a personality test alone in developing a character or base a character off of a personality type but it's certainly extremely helpful. Many personality types also have tumblr pages attached to them as well as many famous people, which is important in deciding how the character should reasonably act within their personality.
Knowing a character's personality type (if of various types, all the better!) can help determine how they will deal with problems and come up with solutions, of who they would be compatible with and why. This is especially helpful if a writer is stuck or if something about a scene doesn't seem to ring quite true.
It's interesting to see how much psychology is a component is in this and I can tell much research has been done on the topic.
It's almost like astrology but it's better and more accurate. If there were MBIT horoscopes in the newspaper, maybe I might actually give them some thought!