Technological advances over the past decade have allowed scientists to study the brain in ways that have led to new insights into how young children develop. There is a new understanding of both the capabilities and vulnerabilities of infants and young children, and this understanding has influenced the work of health workers and teachers. During pregnancy, the basic architecture of the brain is formed. However, some experiences influence brain development during pregnancy, such as maternal health and stress, drug and/or alcohol intake, and the quality of maternal nutrition. Children learn to speak by listening to speech and having language directed at them during "conversation." “ Between 6 and 12 months, babies begin to refine their ability to perceive the speech sounds of their native language compared to those of their non-native language. A human baby's brain has the greatest density of brain cell connectors ( synapses) at age 3. Researchers who have studied the brains of both monkeys and humans have shown that there is a pattern of rapid synapse formation during the early stages of development...