Gilles Fauconnier has said over and over that mappings between conceptual domains are the product of incredibly complex, unconscious processes that are learned over the course of development. It's easy to forget this, though, because we perform such mappings constantly and effortlessly in our everyday cognitive functioning. But all we need to do is look at the trouble that young children have with some mappings that, for us adults, seem perfectly straightforward, to be reminded that Gilles is right. Take, for example, a conversation I recently had with my 7-year old son. He and I were walking along on the sidewalk of a fairly busy street when we came upon a deep hole dug by workers repairing a sewer line. It had rained for several days in a row, so no work had been done on the line, and the hole was now filled with about three feet of water (it was on a steep hill, so it got a lot of runoff). Being a seven-year old, my son found the water-filled hole fascinating, and we had to stop to look at it (being a seven-year old at heart, I was fascinated too). We talked about the water, and why the hole was there, and then he noticed that there was a huge pile of dirt next to the hole. Huge piles of dirt are fascinating to seven-year olds (and seven-year olds at heart) too, so the conversation quickly turned to the pile.
"Why is that dirt there?" my son asked.
"It used to be in the hole," I replied.
A look of confusion appeared on my son's face, followed immediately by the look that seven-year olds get when light bulbs go on in their heads.
"Oh, they had to take it out because it got all muddy with the water."
At first, I didn't understand what he meant, but then I realized what was going on. You see, my statement that the dirt "used to be in the hole" is one that any adult would have understood immediately to mean that the dirt was dug out of the place where the hole now is, creating the hole itself. However, this understanding of the sentence requires a very complex mapping. The hole, which exists now, must be placed in the position that it now exists, but in a time that it did not exist, so that the dirt can be in it. But when the dirt is in it, there is no hole. This seemingly simple mapping was a bit much for my otherwise intelligent son. Thus, when he performed the mapping, the dirt was still in the hole (i.e., there was a hole!) when the water came in, and thus the dirt got muddy and had to be removed (don't ask me why he thought that the dirt had to be removed because it was muddy).
The moral of this story is that sometimes it takes a child to remind a cognitive psychologist that his work isn't as easy as he sometimes believes it is. Just because it's easy to think, doesn't mean that thinking is easy.