An enormous amount of brain development takes place during childhood, particularly early childhood. Because of the central role of experience on brain development, the nature of environmental input in childhood is critical. Nutrition, education, verbal exposure, language, emotional, and interpersonal experience—all critically impact the formation of connections between neurons, the building of neural networks. This kind of environmental input affects which synaptic connections survive and which die off. In this way, early environment becomes hardwired into the child’s brain. With time, these early environmental influences become increasingly difficult and sometimes even impossible to change.