There are many different ways to describe personalities, but one that I’m familiar with is the Myers-Briggs Type Indicator test. Take a look at this handy-dandy chart that I found on Wikipedia. Each character should be assigned a designation as an aid to understanding how and why they do what they do and to predict what they will react to and maybe their motivations. Consider, however ,that each person reacts differently depending on the role of the people they are interacting with, so their Type will change according to circumstance.

( Isabel Briggs Myers graduated first in her class from Swarthmore College in 1919 and wrote a mystery novel, Murder Yet to Come, using typological ideas in 1929, which won the National Detective Murder Mystery Contest that year. )