Chapter 12 - Development

Section 1 - Nature and Nurture: The Enduring Developmental Issue

MAIN IDEA QUESTION

How do psychologists study the degree to which development is an interaction of hereditary and environmental factors?

VOCABULARY

developmental psychology - the branch of psychology that studies the patterns of growth and change that occur throughout life

nature-nurture issue - the issue of the degree to which environment and heredity influence behavior

identical twins - twins who are genetically identical

cross-sectional research - a research method that compares people of different ages at the same point in time

longitudinal study - a research method that investigates behavior as participants age

sequential research - a research method that combines cross-sectional and longitudinal research by considering a number of different age groups and examining them at several points in time

How many bald, six-foot-six, 250-pound volunteer firefighters in New Jersey wear droopy mustaches, aviator-style glasses, and a key ring on the right side of the belt? The answer is two: Gerald Levey and Mark Newman. They are twins who were separated at birth. Each twin did not even know the other existed until they were reunited - in a fire station - by a fellow firefighter who knew Newman and was startled to see his double, Levey, at a firefighter's convention.

The lives of the twins, although separate, took remarkably similar paths. Levey went to college and studied forestry; Newman planned to study forestry in college but instead took a job trimming trees. Both had jobs in supermarkets. One had a job installing sprinkler systems; the other installed fire alarms.

Both men are unmarried and find the same kind of woman - "tall, slender, long hair" - attractive. They share similar hobbies and enjoy hunting, fishing, going to the beach, and watching old John Wayne movies and professional wrestling. Both like Chinese food and drink the same brand of beer. Their mannerisms are also similar - for example, each one throws his head back when he laughs. And, of course, there is one more thing: They share a passion for fighting fires.

The similarities we see in twins separated at birth raise one of the fundamental questions posed by developmental psychology. The question is - How can we distinguish between the environmental causes of behavior (the influence of parents, siblings, family, friends, schooling, nutrition, and all other situations to which a child is exposed) and hereditary causes (those based on an individual's genetic makeup that influence growth and development throughout life)? This question embodies the nature-nurture issue. Nature refers to hereditary factors while nurture refers to environmental factors.

~Psychologists today agree that both interact to produce specific developmental patterns and outcomes. The question has evolved into this: How and to what degree do environment and heredity produce their effects? There are development theories which support both to varying degrees.

~Some theories stress the role of heredity and maturation - the unfloding of biologically predetermined patterns of behavior - in producing developmental change. Maturation can be seen in the development of sex characteristics (such as breasts and body hair). Developmental psychologists study the work of behavioral geneticists and evolutionary biologists. Other theories stress the role of learning, emphasizing the environment's role in development.

~Despite their differences, there are agreements. They agree that genetic factors provide both potential and limits for traits and abilities to emerge. The following are characteristics most affected by heredity. They are not entirely affected, as the environment may play a role.

Physical characteristics - height / weight / obesity / tone of voice / blood pressure / tooth decay / athletic ability / firmness of handshake / age of death / activity level

Intellectual characteristics - memory / intelligence / age of language acquisition / reading disability / mental retardation

Emotional characteristics and disorders - shyness / extraversion / emotionality / neuroticism / schizophrenia / anxiety / alcoholism

~Both sides agree on potential of genetics. EX: If Albert Einstein had received no intellectual stimulation as a child and had not been sent to school, it is unlikely that he would ahve reached his genetic potential. EX: Baseball star Derek Jeter would have been unlikely to display such physical skill if he had not been raised in an environment that nurtured his innate talent and gave him the opportunity to train and perfect his natural abilities.

DETERMINING THE RELATIVE INFLUENCE OF NATURE AND NURTURE

In determining the influence of both, researchers have taken different approaches. In one approach, researchers can experimentally control the genetic makeup of laboratory animals by carefully breeding them for specific traits. Researchers are then able to study animals with identical genetic backgrounds placed in varying environments

~Human twins serve as another important source of information. If identical twins display different patterns of development, those differences have to be attributed to variations in the environment in which the twins were raised. The most useful data comes from identical twins who were separated at birth by sets of adoptive parents and raised apart in differing environments.

~Studies of nontwin siblings who are raised in totally different environments also shed some light on the issue. With similar genetic backgrounds, siblings who show similarities as adults provide strong evidence for the importance of heredity.

~In reverse, researchers may examine people raised in similar environments who have totally dissimilar genetic backgrounds. EX: Two adopted children who have different genetic backgrounds and raised in the same family provides evidence for environmental influence.

DEVELOPMENTAL RESEARCH TECHNIQUES

The most frequently used method is cross-sectional research, which compares people of different at ages at the same point in time. This provides information about differences in development between different age groups. EX: If we were interested in finding intellectual ability in adulthood, we might compare a sample of 25-, 45-, and 65-year-olds who all take the same IQ test. We can then find the average score for each age group. The limit of this approach is that we cannot determine that differences in scores is due to age differences alone. It may reflect the educational attainment of the people represented.

~The second major research strategy is a longitudinal study. Longitudinal research traces the behavior of one or more participants as the participants age. These studies assess change in behavior over time, whereas cross-sectional examines differences among groups of people. Using a longitudinal study to assess the same question of intelligence during adulthood; EX: We give an IQ test to a group of 25-year-olds, then retest them at age 45 and again at 65. From this, we can clearly see how individuals develop. The problem with this research is it requires an enormous expenditure of time as the researcher waits for the participants to get older. Subjects may drop out, move away, or even die as the research continues.

~To make up for the disadvantages of cross-sectional and longitudinal studies, investigators have devised an alternative strategy known as sequential research - an approach which combines cross-sectional with longitudinal by studying different age groups at several points in time. EX: Researchers might examine a group of 3-, 5-, and 7-year-olds every six months for a period of several years.

Section 2 - Prenatal Development: Conception to Birth

MAIN IDEA QUESTIONS

What is the nature of development before birth?

What factors affect a child during the mother's pregnancy?

VOCABULARY

chromosomes - rod-shaped structures that contain all basic hereditary information

genes - the parts of the chromosomes through which genetic information is transmitted

zygote - the new cell formed by the union of an egg and sperm

embryo - a developed zygote that has a heart, a brain, and other organs

fetus - a developing individual from eight weeks after conception until birth

age of viability - the point at which a fetus can survive if born prematurely

teratogens - environmental agents such as a drug, chemical, virus, or other factor that produce a birth defect

THE BASICS OF GENETICS

The one-cell entity established at conception contains 23 pairs of chromosomes. One member of each pair is from the mother, and the other is from the father. Each chromosome contains thousands of genes. Genes produce each person's particular characteristics. Composed of sequences of DNA molecules, genes are the biological equivalent of "software" that programs the future development of all parts of the body's hardware. Humans have some 25,000 different genes.

~Some genes control the heart, circulatory system, brain, lungs, and so forth; others shape the characteristics that make each human unique, such as facial configuration, height, and eye color. The child's sex is determined by a particular set of chromosomes, inheriting an X from the mother and either an X or Y from the father. XX = female, XY = male.

~Geneticists have discovered that genes are partially responsible for a wide variety of personal charcteristics, including cognitive abilities, personality traits, and psychological disorders. Few of these characteristics are determined by single genes. Most traits result from a combination of multiple genes that operate together with environmental influences.

The Human Genome Project

In 2001, scientists were able to map the specific location and sequence of every human gene as part of the massive Human Genome Project. The success of the project started a revolution in health care because scientists can identify particular genes responsible for genetically caused disorders. It has already led to the identification of risk factors in children, and the development of new treatments for physical and psychological disorders.

EX: In gene therapy, genes are injected to correct particular diseases directly into a patient's bloodstream. When the gene arrives at the location of the problem, or potential problem, it leads the body to produce chemicals that can alleviate the danger. In other cases, genes are inserted which replace missing or defective cells.

~The long-term success of gene therapy is unknown, and the number of real diseases it can treat today is still limited. Some recipients of gene therapy have relapsed. Still, the potential uses are growing rapidly. Such disorders as AIDS, cancer, rheumatoid arthritis, and nuclear degeneration are strong candidates for the procedure.

THE EARLIEST DEVELOPMENT

When an egg becomes fertilized by the sperm, the resulting one-cell entity, called a zygote, immediately begins to develop. It starts out as a microscopic speck, which after 3 days, increases to around 32 cells during the germinal period. Two weeks after conception, the development enters the embryonic period, which lasts from week 2 through week 8; he or she is now called an embryo. The embryo grows 10,000 times larger by four weeks, at which point it develops a beating heart, a brain, an intestinal tract, and a number of organs. By week 8, the embryo is about an inch long and has discernible arms, legs, and a face.

~From week 8 until birth is known as the fetal period, and the developing individual is called a fetus. At 16 to 18 weeks, its movements become strong enough for the mother to notice them, while hair and facial features become similar to what the child will have at birth. A lifetime's worth of brain neurons are produced, and the major organs begin functioning - though it still can't survive outside of the womb. If the infant were born prematurely around 24 weeks, it could open and close its eyes; suck; cry; look up, down, and around; and even grasp objects in its hands.

~The fetus continues to grow past 24 weeks, developing fatty deposits under the skin, gaining weight. The fetus reaches the age of viability in which it could survive prematurely at about 22 weeks. At 28 weeks, the fetus weighs less than 3 pounds and may be capable of learning.

EX: One study found that infants of mothers who had repeatedly read aloud The Cat in the Hat by Dr. Seuss before the infants' birth preferred the sound of that particular story to other stories after they were born.

~Before birth, fetuses go through sensitive periods where they are particularly sensitive to certain kinds of stimuli. EX: Drugs. If they are exposed to drugs during these periods, the impact will be significant. Sensitive periods can also occur after birth.

~At the end of the normal 38-week pregnancy, the fetus typically weighs 7 pounds and is about 20 inches in length. Preterm infants - those born before 38 weeks - are not fully developed and are more susceptible to illness, future problems, and even death. Those born before week 30 have relatively poor prospects of health... often times with a 50-50 chance of survival.

Genetic Influences on the Fetus

Normal development through 38 weeks is the case 95-98% of the time with all pregnancies. In the remaining 2-5% of cases, children are born with serious birth defects. A major cause of such defects is faulty genes or chromosomes. Here are some of the common genetic and chromosomal difficulties;

~Phenylketonuria (PKU) - child cannot produce an enzyme required for development, resulting in the accumulation of poisons which cause mental retardation

~Sickle-cell anemia - affects 10% of the African American population. It causes abnormally shaped red blood cells, causing episodes of pain, yellowish eyes, stunted growth, and vision problems.

~Tay-Sachs disease - most often found in Jews of Eastern European ancestry, this is a disease which does not allow the body to break down fat, usually causing the child to die by age 3 or 4.

~Down syndrome - when a zygote receives an extra chromosome, resulting in retardation

Prenatal Environmental Influences

Environmental influences can also affect the fetus. Some of the more profound consequences are brought about by teratogens - drugs, chemicals, viruses or other factors that produce a birth defect. Here are some of the major environmental influences;

~Mother's nutrition - poor nourishment leads to higher susceptibility to dieases and poor development, which can lead to poor mental development

~Mother's illness - diseases such as rubella, AIDS, syphilis, diabetes, and high blood pressure may adversely effect the fetus. AIDS can be passed to the child pre-birth, or by breastfeeding after birth.

~Mother's emotional state - anxiety and tension in the final months of birth can lead to irritable infants who sleep and eat poorly... this is because the autonomic nervous system of the fetus becomes sensitive to chemical changes produced by the mother's emotional state

~Mother's use of drugs - babies may become addicted to drugs the mother is taking. Babies go through withdrawal symptoms after birth and often suffer physical and mental impairment. Even legal drugs can have a tragic effect.

~Alcohol - 1 out of every 750 infants is born with fetal alcohol syndrome, resulting in below-average intelligence, growth delays, and facial deformities

~Nicotine use - smoking can lead to miscarriage and infant death, and other consequences can lead to negative consequences that last a lifetime

Although we have been discussing genetic and environmental factors separately, neither works alone.

Alternative Paths to Conception

In some cases, conception represents a major challenge for some couples. Infertility can be the result of a male producing too few sperm. In other cases, it is due to the advanced age of the parents, use of drugs, or previous cases of sexually transmitted disease. Some remedies have been developed by scientists;

~in vitro fertilization (IVF) - eggs are removed from a woman's ovaries and a man's sperm is used to fertilize the eggs in a laboratory

~gamete intrafallopian transfer (GIFT) and zygote intrafallopian transfer (ZIFT) - a fertilized egg is implanted in a woman's fallopian tubes... in some cases the egg is implanted in a surrogate mother - a woman who agrees to carry the child to term.

Section 3 - Infancy and Childhood

MAIN IDEA QUESTIONS

What are the major competencies of newborns?

What are the milestones of physical and social development during childhood?

How does cognitive development proceed during childhood?

VOCABULARY

neonate - a newborn child

reflexes - unlearned, involuntary responses that occur automatically in the presence of certain stimuli

habituation - the decrease in the response to a stimulus that occurs after repeated presentations of the same stimulus

attachment - the positive emotional bond that develops between a child and a particular individual

authoritarian parents - parents who are rigid and punitive and value unquestioning obedience from their children

permissive parents - parents who give their children relaxed or inconsistent direction and, although they are warm, require little of them

authoritative parents - parents who are firm, set clear limits, reason with their children, and explain things to them

uninvolved parents - parents who show little interest in their children and are emotionally detached

temperament - basic, innate disposition

psychosocial development - development of individuals' interactions and understanding of each other and of their knowledge and understanding of themselves and members of society

trust-versus-mistrust stage - according to Erikson, the first stage of psychosocial development, occurring from birth to age 1 1/2 years, during which time infants develop feelings of trust or lack of trust

autonomy-versus-shame-and-doubt stage - the period during which, according to Erikson, toddlers (ages 1 1/2 to 3 years) develop independence and autonomy if exploration and freedom are encouraged or shame and self-doubt if they are restricted and overprotected

initiative-versus-guilt stage - according to Erikson, the period during which children ages 3 to 6 years experience conflict between independence of action and the sometimes negative results of that action

industry-versus-inferiority stage - according to Erikson, the last stage of childhood, during which children age 6 to 12 years may develop positive social interactions with others or may feel inadequate and become less sociable

cognitive development - the process by which a child's understanding of the world changes as a function of age and experience

sensorimotor stage - according to Piaget, the stage from birth to 2 years, during which a child has little competence in representing the environment by using images, language, or other symbols

object permanence - the awareness that objects - and people - continue to exist even if they are out of sight

preoperational stage - according to Piaget, the period from 2 to 7 years of age that is characterized by language development

egocentric thought - a way of thinking in which a child views the world entirely from his or her own perspective

principle of conservation - the knowledge that quantity is unrelated to the arrangement and physical appearance of objects

concrete operational stage - according to Piaget, the period from 7 to 12 years of age that is characterized by logical thought and a loss of egocentrism

formal operational stage - according to Piaget, the period from age 12 to adulthood that is characterized by abstract thought

information processing - the way in which people take in, use, and store information

metacognition - an awareness and understanding of one's own cognitive processes

zone of proximal development (ZPD) - according to Vygotsky, the level at which a child can almost, but not fully, comprehend or perform a task on his or her own

Called a neonate, a newborn arrives in the world in a form that hardly meets the standards of beauty against which we typically measure babies. Yet ask any parents; Nothing is more beautiful or exciting than the first glimpse of their new born.

THE EXTRAORDINARY NEWBORN

The trip through the mother's birth canal may squeeze the incompletely formed bones of the skull together and squashed the nose into the head. The skin secretes vernix, a white greasy covering, for protection before birth, and the baby may have lanugo, a soft fuzz, over the entire body for a similar purpose. The infant's eyelids may be puffy with an accumulation of fluids because of the upside-down position during birth. These features change during the first two weeks of life as the neonate takes on a more familiar appearance. The neonate develops impressive capabilities that grow at an astounding rate over the next couple of months.

Reflexes

A neonate is born with a number of reflexes - unlearned, involuntary responses that occur automatically in the presence of certain stimuli.

rooting reflex - turn their heads towards things that touch their cheek

sucking reflex - prompts infants to suck things that touch their lips

gag reflex - clear the throat

startle reflex - movements in response to a sudden noise

Babinski reflex - a baby's toes fan out when the outer edge of the sole of the foot is stroked

~These primitive reflexes are lost after the first few months and are replaced with more complex and organized behavior. The ability to move independently grows enormously during the first year of life. Fine-muscle movements become increasingly sophisticated.

3 months - rolling over, grasping rattle

6 months - sitting without support

7 months - standing while holding on

8 months - grasping with thumb and finger

11.5 months - standing alone well

12 months - walking well

15 months - building tower of two cubes

16.5 months - walking up steps

24 months - jumping in place

Development of the Senses: Taking in the World

Although their eyes have a limited ability to focus on objects that are not within a seven- to eight-inch distance from the face, neonates can follow objects moving within their field of vision. They show rudiments of depth perception as they raise their hands up when objects move toward their face.

Infants who see a novel stimulus typically pay close attention to it; as a consequence, their heart rates increase. But if they repeatedly see the same stimulus, their attention to it decrease, as indicated by a return to a slower heart rate. This phenomenon is known as habituation.

~At birth, babies prefer patterns with contours and edges over less distinct patterns, indicating that they can respond to the configuration of stimuli. Furthermore, they are aware of size constancy (objects stay the same size even though the image of them changes with distance).

~Neonates can discriminate facial expressions, and even imitate them. They can react to the facial expressions and moods of their caregivers. This capability provides the foundation for social interaction skills in children.

~By the end of their first month, babies can distinguish some colors from others; after four months they can focus on near or far objects and are able to recognize two- or three-dimensional objects. Sensitivity to visual stimuli becomes three to four times greater at 1 year of age after birth.

~Newborns can distinguish different sounds to the point of being able to recognize their mothers' voices at the age of 3 days. After a couple days of age, they can already distinguish between their native tongue and foreign languages. They can recognize tastes and smells at a very early age. There seems to be a built-in sweet tooth; they prefer liquids that have been sweetened with sugar over their unsweetened counterparts.

INFANCY THROUGH CHILDHOOD

EX: A 10-month old child at the local day-care center suddenly learns how to undo the velcro on his winter hat. He begins to take his hat off at will. Soon, the other children at the day-care follow his lead.

This child has asserted his personality. Throughout the remainder of childhood until age 11 or 12, children develop physically, socially, and cognitively in extraordinary ways.

Physical Development

Physical growth provides the most obvious sign of development during this period. Children usually triple their birth weight in their first year of life. From age 3 to age 13, growth averages a gain of about 5 pounds and 3 inches a year. Furhtermore, the relationship of the size of various body parts to one another changes dramatically as children age. EX: Head of a fetus is disproportionately large, but the body fills out after birth.

Average height/weight by age 20; Boys - 5'11"/155 lbs, Girls - 5'3" / 127 lbs

Development of Social Behavior: Taking on the World

The nature of a child's early social development provides the foundation for social relationships that will last a lifetime. Attachment is the positive emotional bond that develops between a child and a particular individual and is the most important form of social development that occurs during infancy. Developmental psychologists have suggested that human attachment grows through the responsiveness of infants' caregivers to the signals the babies provide, such as crying, smiling, reaching, and clinging. The greater the responsiveness to the child's signals, the more attached the child becomes. Full attachment develops when the infant plays as critical and active of a role as the caregiver in the formation of the bond. Infants who respond positively to a caregiver produce more positive behavior on the caregiver's part.

Assessing Attachment. There is a quick and direct way to measure attachment. Developed by Mary Ainsworth, the Ainsworth strange situation consists of a sequence of events involving a child and (typically) his or her mother. Initially, the mother and baby enter an unfamiliar room, and the mother permits the baby to explore while she sits down. An adult stranger then enters the room; after this the mother leaves. The mother returns and the stranger leaves. The mother once again leaves the baby alone, and the stranger returns. Finally, the stranger leaves, and the mother returns.

~Babies' reactions to this experimental situation vary drastically, depending on their degree of attachment to the mother (according to Ainsworth). One-year-old children who are securely attached employ the mother as a home base; they explore independently but return to her occasionally. When she leaves, they exhibit distress, and they go to her when she returns. Avoidant children do not cry when the mother leaves, and they seem to avoid her when she returns, as if indifferent to her. Ambivalent children display anxiety before they are separated and are upset when the mother leaves, but they may show ambivalent reactions to her return, such as seeking close contact but simultaneously kicking or hitting her. A fourth reaction is disorganized-disoriented; these children show inconsistent and often contradictory behavior.

~The nature of attachment has far-reaching consequences for later development. Children who are securely attached to their mothers tend to be more socially and emotionally competent than are their less securely attached peers. They show fewer psychological difficulties and tend to have more successful romantic relationships. While secure attachment does not guarantee good adjustment later in life, conversely, children who lack secure attachment do not always have difficulties later in life.

The Father's Role. More recent research has highlighted the father's role in parenting. The number of fathers who are primary caregivers has grown significantly, with fathers playing an increasingly important role in their children's lives. In 13% of families, the father is the one who stays home to care for preschoolers. Fathers play with their children in different ways than their mothers. Fathers engage in more physical, rough-and-tumble sorts of activities, whereas mothers play more verbal and traditional games, such as peekaboo. Father and mother attachments to children can be similar, and children can form multiple attachments.

Social Relationships with Peers. By the time they are 2 years old, children become less dependent on their parents, more self-reliant, and increasingly prefer to play with friends. Even when sitting side-by-side, two year olds pay more attention to toys than to one another when playing. As they develop more, they interact more. Cultural factors may also be a factor. EX: Korean-American children engage in less pretend play than thei Anglo-American counterparts. Once children reach school age, they participate in games and activities with teams and rigid rules. This helps them become socially competent.

In short, social interaction helps children interpret the meaning of others' behavior. They learn physical and emotional self-control: They learn to avoid hitting a playmate who beats them at a game. They learn to be polite and control their facial expressions and emotional displays.

The Consequences of Child Care Outside the Home. Almost 30% of preschool children whose mothers work outside the home spend their days in child-care centers. By the age of 6 months, more than two-thirds of infants are cared for by people other than their mothers for part of the day. Do these arrangements outside the home benefit a child's development? If the programs are of high quality, they can. Research shwos that children in high-quality day care arrangements may not only do as well as their peers who saty home with parents, they may actually do better. They generally become more considerate and sociable, and they interact more positively with teachers. They may also be more compliant and regulate their behavior more effectively. Often times, the environment of high-quality day care is more intellectually stimulating. This can lead to higher IQ scores and better language development. In fact, children in care centers sometimes are found to score higher on tests of cognitive abilities than those who are cared for by their mothers or sitters.

On the negative side, children may feel insecure after placement in low-quality child care, or in multiple care settings. Infants in outside care more than 20 hours per week show less secure attachment to their mothers. They may also suffer from a reduced ability to work independently and manage their time effectively when they reach elementary school.

~The key to success for nonparental child care is its quality.

Parenting Styles and Social Development. Parents' child-rearing practices are critical in shaping their children's social competence. Four main categories describe different parenting styles; authoritarian, permissive, authoritative, uninvolved.