According to educational psychologist Susan Engel, curiosity begins to decrease as young as four years old. By the time we are adults, we have fewer questions and more default settings. As Henry James put it, “Disinterested curiosity is past, the mental grooves and channels set.” The decline in curiosity can be traced in the development of the brain through childhood. Though smaller than the adult brain, the infant brain contains millions more neural connections. The wiring, however, is a mess; the lines of communication between infant neurons are far less efficient than between those in the adult brain. The baby’s perception of the world is consequently both intensely rich and wildly disordered. As children absorb more evidence from the world around them, certain possibilities become much more likely and more useful and harden into knowledge or beliefs. The neural pathways that enable those beliefs become faster and more automatic, while the ones that the child doesn’t use regularly are pruned away.