Development in Infancy and Childhood
In utero, the brain develops rapidly, and an infant is born with essentially all of the nerve cells it will ever have; brain development is particularly rapid during the third trimester. However, after birth, neural connections must form in order for the newborn ultimately to walk, talk, and remember. Mark Rosenweig and David Krech conducted an experiment to demonstrate the importance of enriched environments during development. They compared rats raised alone to those that were allowed to use a playground in the company of other rats. Those in the impoverished (solitary) environment developed a thinner cortex with fewer glial cells, cells that support and nourish the brain's neurons. Other studies have demonstrated that stimulation provided by touch or massage benefits both premature babies and infant rats, a fact that argues for providing an enriched environment for a developing organism.
Infants are born with a surprising number of unlearned (innate) reflexes, that is, unlearned responses to stimuli.
The Moro reflex is an outstretching of the arms and legs in response to a loud noise or sudden change in the environment. The infant's body tenses; arms are extended and then drawn inward as if embracing.
The Babinski reflex is an outward projection of the big toe and fanning of the others when the sole of the foot is touched.
The sucking reflex occurs when an object touches the lips.
The rooting reflex is the turning of an infant's head toward a stimulus such as a breast or hand.
The grasping reflex is the vigorous grasping of an object that touches the palm.
The plantar reflex is the curling under of the toes when the ball of the foot is touched. Physicians sometimes use these reflexes to assess the rate of development. Gradually, learned responses replace the reflex actions as an infant becomes more responsive to the environment.
- Although the rate of motor development can vary, the developmental sequence is the same. On average, an infant will learn to roll over at 2-1/2 months, sit without support at 6 months, and walk alone at 12 months. The growth and body development from infant to child occurs in a cephalocaudal direction; that is, the head and upper trunk develop before the lower trunk and feet.
Sensory and perceptual development Newborn infants can and do respond to a wide range of environmental stimuli. All human senses function to some degree at birth; touch is the most highly developed and vision is the least developed sense. At the age of 3 months, however, most infants can recognize a photograph of their mother. An infant's ability to perceive depth has been studied extensively with an apparatus called a visual cliff, a box with a glass platform that extends over a drop of several feet. An adult (mother or experimenter) stands on one side of the glass bridge and calls to the child, who is on the other. Eleanor Gibson and Richard Walk, in a well‐known study, found that at about 6 months babies balk at crawling over the edge of the “cliff.” Such a response indicates that depth perception is present at this age.
Cognitive development. The term cognitive development refers to the development of the ability to think and to mentally represent events and to manipulate symbols.
Jean Piaget, a pioneer in the study of children's thinking, was concerned with the way a child organizes information from the environment and adapts to it. He believed that every behavioral act requires two dynamic processes of adaptation: assimilation and accommodation. Assimilation is the process of acquiring new information about the world and fitting it to already acquired information. A child who calls all grown males “daddy,” based on the child's perception that they and “daddy” are in some way similar, is practicing assimilation. Accommodation is the process of creating a new concept to handle new information; for example, children come to realize that all toys don't belong to them, that some belong to other children.
Piaget, who had a strong biological background, proposed four stages of development: sensorimotor, preoperational, concrete operational, and formal operational. According to Piaget,
During the sensorimotor stage (birth to age 2) infants develop their ability to coordinate motor actions with sensory activity. At the start of this stage, children's behavior is dominated by reflexes, but by the end of it, they can use mental images. Also during this stage, children acquire the concept of object permanence, realizing that objects still exist even when the objects are not present.
During the preoperational stage (ages 2 to 7 years), children improve in the use of mental images and symbolic thought. Most of the thinking of children of this age, however, is egocentric (self‐centered).
During the concrete operational stage (ages 7 to 11 years), children begin to develop many concepts and to organize the concepts into classes and categories.
During the formal operational stage (ages 11 years and beyond), children learn to use and to manipulate abstract symbolic concepts, develop and mentally test hypotheses, and work mental problems. That is, they can reason.
Although Piaget's theories are subject to some criticism, they are widely used and important in guiding research in childhood cognitive development.
Language development. Language acquisition is one of the most important aspects of a child's development.
Moral development. Lawrence Kohlberg proposed that moral development occurs in three levels, with two stages at each level.
The preconventional level:
At stage 1, punishment orientation, judgments are guided by the prospect of punishment.
At stage 2, pleasure‐seeking orientation, activities are undertaken primarily to satisfy one's own needs; needs of others are important only as they relate to one's own needs.
- At stage 3, good girl/good boy orientation, behavior is engaged in that brings approval or pleases others in a child's immediate group.
- At stage 4, authority orientation, behavior is influenced by respect for authority, performing one's duty, and doing what is right.
The postconventional level:
- At stage 5, contract and legal orientation, behavior is based on support of rules and regulations because society's right to exact such support is accepted.
- At stage 6, ethical and moral principles orientation, behavior is directed by self‐chosen ethical and moral principles.
Kohlberg found that the first two stages are reached by most children, that stages 3 and 4 are reached by older children and most adults, but that the stage 6 is reached by only 20% of the population.
Carol Gilligan examined certain differences between the moral development of males and that of females. In younger children, she found that girls are more concerned with a morality based on caring and boys with a morality based on justice. Gilligan proposed that this gender difference is in part due to children's relationship with their mother.
Social development. Social development begins at birth as a child forms an attachment (a strong emotional bond) with the primary caregiver(s), usually the mother. Harry Harlow studied attachment deprivation with baby monkeys raised in isolation. Although their physical needs were met and they were given surrogate mothers made of cloth, these monkeys suffered severe behavior pathologies. They recovered if the isolation was limited to three months, but longer periods produced abnormal adults. Ethically, this type of study could not be conducted with humans, but parallels have been found with children reared in cold, isolated, emotionally deprived environments. Emotional attachments to caregivers are thought to be essential for social development.
Konrad Lorenz studied imprinting, a rapid and relatively permanent type of learning that occurs for a limited time (called a critical period) early in life, particularly in birds. Baby ducks learn to follow their mother if they see her moving during the first 30‐hour period after their birth. If, however, they don't see their mother, they can imprint on and follow a human or even a moving object instead. Imprinting demonstrates that attachments by the young to a parent can occur early and can have lifelong consequences.
The term gender stereotyping refers to patterns of behavior expected of people according to their gender. The development of gender‐related differences is complex. Gender stereotyping occurs not only because of parental differences in rearing children of each gender but also because of socialization experiences. Eleanor Maccoby has observed that children with widely different personalities play together simply because they are of the same gender.
Personality development. Developmental psychologists also study personality development in children.