 developed before birth are crucial, their primary purpose is biological (Simmons & Sheehan, 1997). It is during the child's first months and years of growth and development that nature and nurture mesh, until they become "intertwined and inseparable" (Simmons & Sheehan, 1997, p. 6). When a child is born, his brain has 100 billion neurons, which in turn make over 50 trillion synapses (Begley, 1997). Afterwards, especially within the first three years of life, the brain undergoes a series of phenomenal changes. During this period, many more connections among neurons are created - literally trillions more than the brain can possibly use. Over time, those connections that are seldom or never used are eliminated (Nash, 1997). Researchers report that the eliminated connections are not predetermined, as was once thought. Rather, the manner in which a child is raised affects how the brain chooses to wire itself for life (Simmons & Sheehan, 1997).
The concept of "critical periods" for brain development was only a hypothesis prior to a series of innovative experiments conducted in the 1960s and early 1970s. Two researchers, David Hubel and Torsten Wiesel, conducted investigations on how cats' brains were wired for sight. They discovered that by withholding stimuli to a kitten's eyes during a critical period, they blocked the development of connections between the eye and the visual cortex, connections that are necessary for sight. The researchers also discovered that after the critical period had passed, attempts to produce the connections were useless (Begley, 1996; Simmons & Sheehan, 1997). Consequently, according to Dr. Carla Shatz, a neurobiologist at the University of California at Berkeley, "It [the Hubel and Wiesel research discovery] forever changed the way we thought about brain development" (Simmons & Sheehan, 1997, p. 5). Referencing the critical period studies, Sharon Begley (1996) states:
[The studies] suggest that with the right input at the right time, almost anything is possible. But they imply, too, if you miss the window, you are playing with a handicap. [The studies] offer an explanation of why the gains a toddler makes in Head Start are so often evanescent: this intensive instruction begins too late to fundamentally rewire the brain. (p. 56)
Recognizing and taking advantage of the various windows of opportunity are paramount to young children's healthy development. A child's brain development suffers if the child is denied the opportunity to live in a stimulating environment (Nash, 1997). Nash reports, "Researchers at Baylor College of Medicine, for example, have found that children who don't play much or are rarely touched develop brains 20 percent to 30 percent smaller than normal for their age" (p. 51). Consequently, the research emphasizes the positive effects of hands-on parenting, which includes talking with and cuddling infants and toddlers, as well as providing them with stimulating experiences (Nash, 1997).
For centuries, parents have understood the newborn's basic need for safety, nourishment, warmth, and nurturing. Now, research offers remarkable insights about human development from birth to age 3, substantiating the view that parents and other adult caregivers are a vital component in the child's development (Carnegie Corporation, 1997).
Julie J. Newberger (1997), communication specialist of the National Association for the Education of Young Children, says:
Stimulated in part by growing concern about the overall well-being of children in America, the [brain research] findings affirm what many parents and caregivers have known for years: (a) good prenatal care, (b) warm and loving attachments between young children and adults, and (c) positive, age-appropriate stimulation from the time of birth really do make a difference in children's development for a lifetime. (p. 4)
Kantrowitz (1997) echoed this sentiment, stating "Cutting-edge science is confirming what wise parents have also known instinctively: Young children need lots of time and attention from the significant adults in their lives" (p. 7)