The Gough Heilbrun Adjective Check List (ACL) is an assessment used to identify common psychological traits. It was developed by Harrison G. Gough and Alfred B. Heilbrun, Jr. The list contains 300 adjectives such as confident, poised, and cautious. Assessment takers choose the adjectives that they think best describe themselves (or someone else). Any number may be selected from the list of adjectives. The 300 adjectives correlate to 24 scales. 15 of the scales assess needs or desires, while the other 9 scales assess "attributes, potentialities, and role characteristics". The ACL also measures, to some extent, creativity and intellect.
Now, most of us can't afford to buy copies of the manual and tests. However, we are writers and it should be a simple matter to generate a list of 50 to 100 adjectives describing personality traits. Choose one of your characters, sit down, and really think about it. Which traits would you select to describe him/her? More importantly, which would your character choose for himself? Is he an introvert masquerading as an extrovert (thereby annoying people by "trying too hard)? Is your character self-aware, honest, have insight into his own strengths and weaknesses? Or is he narcissistic, suffering from delusions of grandeur, or totally out of touch with how he appears to others? Perhaps he carries an ideal vision of himself which doesn't translate into the real world.
Try this exercise with a beta reader(s): have them choose 5-10 adjectives which describe the main character. How do they compare with the adjectives which you have chosen? Is there overlap? If not, why not?
Just for fun, here are a few adjectives that you might not recognize. :-)
(BTW, if you are interested in purchasing the ACL, here is the LINK. )