4.1: Physical Development (Ob1)

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Introduction

Welcome to the story of development from infancy through toddlerhood; from birth until about two years of age. Researchers have given this part of the life span more attention than any other period, perhaps because changes during this time are so dramatic and so noticeable and perhaps because we have assumed that what happens during these years provides a foundation for one’s life to come. However, it has been argued that the significance of development during these years has been overstated (Bruer, 1999). Nevertheless, this is a period of life that contemporary educators, healthcare providers, and parents have focused on most heavily. We will examine growth and nutrition during infancy, cognitive development during the first two years, and then turn our attention toward attachments formed in infancy.

Overall Physical Growth

The average newborn in the United States weighs about seven and a half pounds and is about twenty inches in length. For the first few days of life, infants typically lose about five percent of their body weight as they eliminate waste and get used to feeding. This often goes unnoticed by most parents, but can be a cause for concern for those who have a smaller infant. This weight loss is temporary, however, and is followed by a rapid period of growth. By the time an infant is four months old, it usually doubles in weight and by one year has tripled it birth weight. By age two, the weight has quadrupled. The average length at one year is about twenty six to thirty two inches.

Body Proportions

Another dramatic physical change that takes place in the first several years of life is the change in body proportions. The head initially makes up about fifty percent of our entire length when we are developing in the womb. At birth, the head makes up about twenty five percent of our length (think about how much of your length would be head if the proportions were still the same!). By age twenty five it comprises about twenty percent our length. Imagine now how difficult it must be to raise one’s head during the first year of life! And indeed, if you have ever seen a two to four month old infant lying on the stomach trying to raise the head, you know how much of a challenge this is.