Book excerpt: Whether our personality, intelligence, and behavior are more likely to be shaped by our environment or our genetic coding is not simply an idle question for today's researchers. There are tremendous consequences to understanding the crucial role that environment and genes each play. How we raise and educate our children, how we treat various mental diseases or conditions, how we care for our elderly--these are just some of the issues that can be informed by a better understanding of brain development. In The Great Brain Debate, the eminent neuroscience researcher John Dowling looks at these and other important issues. The work that is being done on the connection between the brain and vision, as well as the ways in which our brains help us learn new languages, are particularly revealing. From this groundbreaking new research, Dowling explains startling new insights into how the brain functions and how it can (or cannot) be molded and changed. By studying the brain across the spectrum of our lives, from infancy through adulthood and into old age, Dowling shows the ways in which both nature and nurture play key roles over the course of a human lifetime.