I was also told that I'm a concrete thinker. I feel like there must be a difference between the terms - I was diagnosed with impairments in abstract reasoning through my executive functioning tests (hence, I'm a concrete thinker), but I'm not a literal thinker at all when it comes to language. I easily draw information from figurative speech, sarcasm, and literary symbolism. At the same time, I can hardly do high school geometry. Perhaps "literal thinker" is meant to be applied to language impairments, while "concrete thinker" has more to do with truly abstract concepts, like higher math and philosophical ideas.
_________________
I have not the kind affections of a pigeon. - Ralph Waldo Emerson