From a Single Cell to a Baby

The single fertilized cell divides into many cells which gradually assume specialized forms and functions. The earlier stage of development is called the embryo, which later develops into the fetus.

The growth follows a sequence of development from general to specific, from head to tail and from central to peripheral. Some reflexes are present at birth and others do not appear until months after birth. There is some development of the child's sense organs before birth but it is doubtful whether they provide the infant with information about his environment comparable to the experiences of older children and adults.

Many lower animals have well-coordinated behavior at birth, while others, including the human newborn infant are quite helpless. But this helplessness of the human newborn infant is not an indication that its first behavior responses are just a mass of uncoordinated movements. Detailed studies allowing a frame by frame analysis show a number of reactions that occur, even without such specific forms of external stimulation as pinching the skin or sounding loud noises near the infant.

These internally generated behaviors include crying, stretching, sneezing, chewing, sucking, smiling and mouthing. The behaviors are distinct patterns, each characteristically different from every other. However, these are total body responses. When the infant cries, 'he cries all over.' Only in later development is smiling, specifically restricted to the facial region. And of course, as adults, we have learned to smile even when we are in a state of tension.

By birth, certain isolated responses to external stimulations have been partially developed in the infant. When a sense-receptor mechanism is activated, a characteristic motor response to the particular stimulation follows; an early example of this reflex behavior is the sucking response. Other forms of reflex behavior, such as the plantor reflex of the foot, do not appear until months after birth.

The sucking reflex, present at the birth, can be elicited by touching the lips or cheek, but sucking movements in responses to cheek stimulation gradually narrow down to a point where a stimulation of the cheek will no longer elicit the response. The reflex area has become specially localized to the region of the lips. This shows the general sequence of development not only for the response, but for the area of stimulation as well.

Studies show that at birth the newborn can make visual discrimination between lights of different brightness. Sensitivity to sound, taste, and smell are noticeable a few days after birth. Babies show responses to changes in temperature also, the senses of hunger and thirst and pain seem to function well in the newborn.