Developmental Stages

DEVELOPMENTAL STAGES

Development actually begins prenatally and extends through life. In prenatal development, there are three physiological stages: germinal, embryonic, and fetal. The baby develops differently during each of these stages.

In the germinal stage, which is at 1 to 2 weeks gestation, conception occurs with the fertilization of the egg to form a zygote. The zygote is a single-celled structure with a certain genetic makeup. The zygote will divide through mitosis to make four, eight, sixteen, and more cells. Fewer than half of all zygotes will survive past this stage. Cells gradually become more specialized in order to form certain tissues and organs. The germinal stage is prior to implantation.

The embryonic stage is from weeks three through eight. It starts with implantation and the formation of the placenta, which connects the embryo to the uterine wall. The basic structures will develop, such as the head, chest, and abdominal cavity. Immature organs form and the heart beats. The brain and spinal cord develop.

In the fetal stage, weeks 9 through 40, the embryo becomes a fetus. The tail disappears and the sex organs develop. There is maturation of all of the major organs, including the brain. Senses such as hearing and the sensation of pain develop and the size of the fetus increases dramatically. Figure 12 shows the different stages of fetal development:

Figure 12.

There are both genetic and environmental influences on fetal and embryonic development. This is the time for good prenatal care so that the environment is optimal for the fetus. In some cases, women should have preconception care in order to maximize the woman s health before she becomes pregnant.

There are also influences of teratogens, which are environmental agents that can damage or kill the embryo or fetus. One such teratogen is alcohol. Alcohol consumption in pregnancy can lead to fetal alcohol syndrome, which can be severe enough to have a lifelong impact on the child. Facial features and head size can be affected, with an increased risk of low IQs and ADHD (attention deficit hyperactivity disorder).

With each teratogen, there will be a sensitive or critical period that will be when the teratogen is most dangerous. In many cases, this will be early in the pregnancy, when

things like facial and heart development are taking place. Certain teratogens will affect the brain, which continues to develop throughout the prenatal period.

The next stage in development is infancy. The newborn will have certain newborn reflexes that are lost shortly after birth. Some of these reflexes are adaptive, such as the rooting and sucking reflexes. Other reflexes are interesting but have no real purpose. Infants have good senses of smell, touch, and hearing but do not have good vision. They will prefer human faces and certain voices and can detect the smell of their mother.

Physical development is rapid from infancy to early childhood. Height and weight increase dramatically and there is a constant improvement in small and large motor skills. Language develops during this time and also progresses rapidly. Growth will slow somewhat between four and six years of age but increases after that in girls. Girls growth outpaces the growth of boys until they reach puberty, which happens sooner in girls compared to boys.

While there is no increase in brain cells after birth, these brain cells will mature and store increasing amounts of information in childhood. Blooming is the phenomenon of rapid neural growth in childhood. After blooming, there is pruning, which involves a reduction in neural connections. This is believed to help the brain be more efficient for mastering complex skills. Both blooming and pruning happen during childhood and up until adolescence.

There are two types of motor skills—both of which involve the movement of the body. Fine motor skills involve things like writing and handling small objects, usually with the hands. Gross motor skills happen with large muscle groups and involve things like running, jumping, and staying balanced. There are specific motor skill milestones that need to be reached by a certain age if the child is developing normally.

Mile stones such as sitting happen at around six months of age. Crawling occurs at around nine months of age, and walking develops by one year of age. Older children can kick balls, walk up and down stairs, pedal a bicycle, use scissors, and catch a ball. There are language and cognitive skills that develop in infancy, as a toddler, and in the preschool years.

Language skills are part of cognitive development that can be easily studied. Babies have certain preverbal language skills and can gesture before they learn words. Eventually, the attain different levels of speech, which is completely consistent across different cultures and populations of the world. First words that have meaning happen at around 12 months of age, even though they do not always resemble the correct adult word. Language is both innate and develops through interactions with others.

Psychosocial development involves forming healthy attachments to others, which usually occurs during infancy. There are differences in attachment between children raised in different environments. Research on infant monkeys indicated that they preferred a soft surrogate monkey that did not deliver milk versus a wire monkey that delivered milk.

John Bowlby developed theories on attachment, which is the affectional bond that the baby has with its mother. It must develop before there can be normal emotional and social development. Secure attachment is what is strived for with every baby but babies who are abused or neglected do not see it that way. The Strange Situation study looked at how children responded to a stranger in the room both with and without the mother.

Four types of attachment were described: secure attachment, avoidant attachment, resistant attachment, and disorganized attachment. The most common type is secure attachment, in which the mother is looked to for comfort. In avoidant attachment, the child is unresponsive to the parent and treats the stranger the same way. In resistant attachment, the child clings to the mother and cannot explore the room. They later become angry with the mother for leaving, which stems from inconsistent responses to the child. Disorganized attachment is seen in abused children, who sometimes run away when the mother returns to the room.

Children at about 18 months of age develop a self-concept and see themselves as different from the baby they see in the mirror. They will increase their social behavior so that they learn to share and cooperate with other children. By age 4, there is little separation anxiety and an increased identification of themselves as a member of a group. School age children will compare themselves with their peers. What starts as toddlers gets more fully developed as teenagers.