I'm actually a psychiatrist, not a psychologist, and part of what makes analyzing Mr. Trump so challenging, is that beyond his very likely narcissism, he indisputably has ADHD. (I wrote a book and a year of weekly medium.com posts on this.) One consequence of his ADHD is that he spouts off whatever is at the top of his mind, without filters. Some of his followers find this charming, or a sign of his truthiness (mistaking honesty for candor), but it certainly makes him harder to predict than if he were simply an extreme narcissist.