Not entirely surprising. I remember an exhibit at the COSI Science Museum in Toledo, Ohio with some 4th and 5th graders I taught years ago that I think demonstrated the concreteness of our thinking as we grow older.
There was a room with a tilted floor that children and adults could walk through. The walls though, rather than being still in square with the tilted floor, were all leaning toward the high side of the room, but not exactly vertical. I remember being surprisingly disoriented, some other adults I was with could hardly stand in the room with their eyes open without being subject to a feeling of vertigo and slight nausea. Children, on the other hand, would walk through the room and notice the changes, but they did not seem to have balance issues or feelings of sickness. Turns out, a description of the exhibit on the wall explained that adults, being far more used to seeing walls, doorways, ceilings, and other structures at ninety degree angles had a greater difficulty dealing with the information that was out of their typical cognitive schema than would children whose mental schema of the world was much more malleable. Makes me wonder what other perceptual differences there are between children and adults.
On the perceptiual differences, I think that adults are more prone to develop, both intentionally and unintentionally, fixed mindsets on the environment. As I get older, I feel that we tend to migrate towards the simple and common, and children remain open learners, being that there is new stimulation around every corner. They are used to adapting, because they must, to learn how to survive (primally speaking), yet we can pick and choose out of several way; often we choose the path of least resistance, which makes us weaker.
I love reading about these kinds of things: how we think, how babies think, how they learn, etc. One of my favorite Ted talks: http://www.ted.com/talks/deb_roy_the_birth_of_a_word.html From the description:MIT researcher Deb Roy wanted to understand how his infant son learned language -- so he wired up his house with videocameras to catch every moment (with exceptions) of his son's life, then parsed 90,000 hours of home video to watch "gaaaa" slowly turn into "water." Astonishing, data-rich research with deep implications for how we learn.
It's interesting that the human mind may go through stages that optimize it according to developmental needs. Perhaps abstract thinking is more important at 18 months and then again later in life, than it is at 5? I was recently watching Ken Robinson's talk asking Do Schools Kill Creativity? In it, Ken tells a story about a little girl that is in an art class; the teacher approaches her and asks, "what are you painting?" and the little girl responds, "I'm painting God." The teacher responds by saying, "but nobody knows what God looks like!" To which the little girls responds, "well, they will in a minute." I love that. I wonder how much of a kids ability to do abstract reasoning is forced out of them through our antiquated educational process?