.... we used to use proverbs to assess concrete vs abstract thinking ....

That's very interesting, Zed.
I remember that when I was quite young (6 or 8 yrs old, I guess) I used to love Æsop's Fables, and the concrete examples of the stories helped me to develop an understanding of the abstract concepts of the "moral" to each story.
These days, I do find Æsop more than a little tedious - I no longer need the example to comprehend the message of the moral.
And, to me, the difference between the concrete and abstract is well summed up by the story and the moral in those tales.