I am a slow thinker if I need to do some calculations that require a precise answer. For me, it's a memory thing. To be fast you need to memorize patterns, algorithms and data, whether you do it consciously or not. You also need to have a good working memory.

I have a terrible long term memory and about an average working memory.

As a work around, when I don't have to come out with precise answers I got quite good at making aproximations.

As another work around, my brain tries to use data that it can recall with ease such as very fresh data, instead of trying to remember things that might take some time to remember or not remember at all.

While I enjoy debating and long talks about tech, science, culture, history, art etc, I tend to concentrate on stuff I can deduct or think on the moment such as ideas instead of trying to remember stuff.

As a consequence, I tend to suck at job interviews when I am asked to recite things from memory. So before interviews I kind of have to review most asked questions.