If the earlier edition of the handbook represented the coming of age of the field of early childhood intervention, the presentation of this edition surely marks the beginning of its maturity. As developmental psychologists know well, each stage of development brings characteristic triumphs and challenges, with occasional setbacks and recurrences of the previous stage's struggles, not entirely abandoned as the young move forward into new stages along their growth trajectory. Our young field is no exception. A decade later, we are stronger, wiser, and capable of more complex tasks and deeper understanding than we were, yet old difficulties reassert themselves and continue to beset us, and there is still much to learn. Just as social expectations increase as the individual reaches maturity, the responsibilities of the field of early intervention have been accruing apace. We know more now; we have a great deal to do.

Throughout the 1990s, we have witnessed great breakthroughs in the field of brain development. Recent brain research has demonstrated with unprecedented certainty the importance of early experience in influencing the actual growth and development of neural pathways in the individual (Kotulak, 1996). During the years from 3 to 10, the brain is more densely “wired” than at any other time in the child's life. This means that there is literally a profusion of synapses connecting brain cells that are present in the growing child.