Our Brain is constantly learning and reshaping neural pathways. We all have different but similar personalities. Learning to recognize them is not complex. Realizing the difference is. If we compared personalities to cookies you would see all chocolate chips have the same basic ingredients until you choose the chips or add a nut. All Oatmeal cookies are the same until you add or minus icing....nuts or not.
Identifying the personality puts you on a path of discovery. The Main path will be the same as every other same cookie, but the side paths will be new. You may find an outgoing personality that shuts down in the presence of a timid personality. Recognizing the tells would be a great asset in dealing with people you either want to get close to or get them to stop doing harm.
This statement is true on many levels. In opening some one up, their minds put guards down that you didnt even know were there. We do that by staying on that main path. Letting people become comfortable with you. The more open you are the faster the process. No one wants to be alone in their weirdness.