Basically, Ms. Kempton argues that people fall into categories, and based on that, a writer can immediately spot dialogue which is out of character. The idea intrigued me, especially since there's a nifty test to type yourself and your characters. (I'm an investigator-achiever.)
Per the Ennegram Institute:
So if I'm a 5-3, my thinking center motivates me, then my feeling center kicks in. Anxiety is a driver for me, followed up by shame. So I'm an introvert who wants to "perfom well and overcome".
This is getting a little personal, so I think I'll stick to evaluating my characters instead.