Developmentalists generally agree that the way children manage and understand information changes rather dramatically after age 6.
Most parents are pretty aware of this too; children just seem more mature in the way they reason. It is clearly much more than simply having learned more facts and more words. There are different ideas about what exactly causes the change. Neurological development, growth of memory and changes in the way information is processed all seem to be involved.
One clear change is that children this age . . .