chapter 1-3 outline
chapter 1-3 outline PSY 0310
Popular in Developmental Psychology
Popular in Psychlogy
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Date Created: 11/19/15
Chapter 1: Methods for Studying Child Development (pgs 22-36) I. The Scientific Method A. The basic assumption of the scientific method is that all beliefs, no matter how probable they seem and no matter how many people share them, may be wrong. B. Until beliefs have been tested, they must be viewed as hypotheses. C. The scientific method has four basic steps 1. Choosing a question to be answered 2. Formulating a hypothesis regarding the question 3. Developing a method for testing the hypothesis 4. Using the data yielded by the method to draw a conclusion regarding the hypothesis D. What distinguishes scientific research from nonscientific approaches is the methods used to test the hypotheses. These methods yield high-quality evidence. E. The importance of Appropriate Measurement 1. For the scientific method to work, researchers must use measures that are directly relevant to the hypotheses being tested 2. Relevancy, reliability and validity determine whether a measure is a good one. 3. Reliability a. The degree to which independent measurements of a behavior under study are consistent is referred to as reliability. i. Interrater reliability indicates how much agreement there is in the observations of different raters who witness the same behavior ii. Observations are qualitative or quantitative b. Test-retest reliability is attained when measures of a child’s performance on the same test, administered under the same conditions, are similar on two or more occasions. i. A lack of this would make it impossible to know which result (if either) accurately reflected each child’s status 4. Validity a. The validity of a test refers to the degree to which it measures what it is intended to measure. b. Internal validity refers to whether effects observed within experiments can be attributed with confidence to the factor that the researcher is testing. c. External validity refers to the ability to generalize research findings beyond the particulars of the research in question II. Contexts for Gathering Data About Children A. Interviews 1. The structured interview is a research procedure in which all participants are asked to answer the same question a. It is especially useful when the goal is to collect self- reports on the same topics from everyone being studied. b. Asking large numbers of children identical questions about their feelings and beliefs provides a quick and straight-forward way for researchers to learn about children’s beliefs and attitudes. 2. The clinical interview is a procedure in which questions are adjusted in accord with the answers the interviewee provides a. It is especially useful for obtaining in-depth information about an individual child. b. It is tailored to the individual. B. Naturalistic Observation 1. Naturalistic observation is examination of ongoing behavior in an environment not controlled by the researcher. a. It is the method of choice when the primary goal is to describe how children behave in their usual environments. b. In this approach, observers try to remain in the background, allowing them to see the relevant behaviors while minimizing the chances that their presence will influence those behaviors. c. Limitations of naturalistic observation: i. Naturally occurring contexts vary on many dimensions, so it is often difficult to know which ones influenced the behavior of interest. ii. Many behaviors of interest occur only occasionally in the everyday environment. C. Structured Observation 1. Structured observation is a method that involves presenting an identical situation to each child and recording the child’s behavior a. Researchers design a situation that will elicit behavior that is relevant to a hypothesis and then observe how different children behave in that situation. b. They then relate the observed behaviors to characteristics of the child, such as age, sex, or personality, and to the child’s behavior in other situations that are also observed. 2. Structured observation offers an advantage over naturalistic observation: a. It ensures that all the children being studied encounter identical situations. b. This allows direct comparisons of different children’s behavior in a given situation and makes it possible to establish the generality of each child’s behavior across different tasks. 3. Limitations to structured observation: a. Doesn’t provide as extensive information about individual children’s subjective experience as interviews. b. Can’t provide open-ended data. III. Correlation and Causation A. People differ along variables, attributes that vary across individuals and situations, such as age, sex, and popularity. 1. A major goal of child-development research is to determine how these and other major variables are related to one another, both in terms of associations and cause-effect relations. B. Correlational Designs 1. Correlational designs are studies intended to indicate how two variables are related to each other a. The primary goal is to determine whether children who differ in one variable also differ in predictable ways in other variables. 2. The associate between two variables is their correlation. a. When variables are strongly correlated, knowing a child’s score on either variable allows accurate prediction of the child’s score on another b. Correlations range from 1.00 (strongest positive) to -1.00 (strongest negative). i. The direction is positive when high values of one variable are associated with high values of the other and low values of one are associated with low values of the other. ii. The direction is negative when high values of one are associated with low values of the other. C. Correlation Does Not Equal Causation 1. The direction-of-causation problem is the concept that a correlation between two variables does not indicate which, if either, variable is the cause of the other. 2. The third-variable problem is the concept that a correlation between two variables may stem from both being influenced by some third variable. 3. One major reason researchers use correlational designs is that the influence of many variables (age, sex, race, social class, etc.) can’t be studied experimentally since they can’t be manipulated. 4. Correlational designs are also useful when the goal is to describe relations among variables rather than to identify cause-effect relations among them. D. Experimental Designs 1. Experimental designs are a group of approaches that allow inferences about causes and effects to be drawn 2. Random assignment is a procedure in which each child has an equal chance of being assigned to each group within an experiment. a. This is crucial for being able to infer that it was the varying experiences to which the groups were exposed in the experiment that caused the later differences between them. b. When groups are created through random assignment and include a reasonably large number of participants, initial differences between groups tend to be minimal. 3. Experimental control is the ability of researchers to determine the specific experiences that children have during the course of an experiment 4. Children in the experimental group are presented with the experience of interest while children in the control group are not presented the experience of interest but in other ways are treated identically. 5. The experience of interest is known as the independent variable. 6. The behavior that is hypothesized to be affected by exposure to the independent variable is the dependent variable. IV. Designs for Examining Development A. Cross-Sectional Designs 1. Cross-sectional designs are a research method in which children of different ages are compared on a given behavior or characteristic over a short period a. Studies changes and continuities with age. 2. Useful for revealing similarities and differences between older and younger children 3. However, they do not yield information about the stability of behavior over time or about the patterns of change B. Longitudinal Designs 1. Longitudinal design is a method of study in which the same children are studied twice or more over a substantial length of time 2. Studying the same children over long periods involves the difficult task of locating the children for each re- examination 3. Used primarily when the main issues are stability and change in individual children over time. C. Microgenetic Designs 1. Microgenetic design is a method of study in which the same children are studied repeatedly over a short period. 2. The idea of the approach is to recruit children who are thought to be on the verge of an important developmental change, heighten their exposure to the type of experience that is believed to produce the change, and then intensively study the change as it’s occurring. 3. Microgenetic designs differ from longitudinal ones in that the typically include a greater number of sessions presented over a shorter time. 4. The counting-on strategy is counting up from the larger addend the number of times indicated by the smaller addend V. Ethical Issues in Child-Development Research A. The Society for Research on Child Development (SRCD) formulated a code of ethical conduct to follow 1. Be sure the research doesn’t harm the child physically or psychologically 2. Obtain informed consent for participating in the research from parents or legal guardian 3. Preserve individual participants’ anonymity 4. Discuss with parents or guardians any information yielded by the investigation that is important for the child’s welfare 5. Try to counteract any unforeseen negative consequences that arise during the research 6. Correct any inaccurate impressions that the child may develop in the course of the study Chapter 2: Prenatal Development (pgs 40-56) I. Conception A. Each of us originated as a single cell that resulted from the union of a sperm from our father and an egg from our mother. These are gametes. 1. Gametes are produced through meiosis. B. The process of reproduction starts with the launching of an egg from on of the woman’s ovaries into the adjoining fallopian tube. 1. As the egg moves through the tube toward the uterus it emits a chemical substance that acts as a signal that attracts sperm towards it. 2. If sexual intercourse takes place near the time the egg is released, conception, the union of sperm and egg, will be possible 3. As soon as one sperm’s head penetrates the outer membrane of the egg, a chemical reaction seals the membrane, preventing other sperm from entering. 4. The fertilized egg, known as a zygote, now has a full component of human genetic material. C. Periods of prenatal development: 1. Conception to 2 weeks- Germinal: Begins with conception and lasts until the zygote becomes implanted in the uterine wall. Rapid cell division takes prdce. th 2. 3 to 8 week- Embryonic: Following implantation, major development occurs in all the organs and systems of the body. Development takes place through the processes of cell division, cell migration, cell differentiation, and cell death, as well as hormonal influences. 3. 9 week to birth- Fetal: Continued development of physical structures and rapid growth of the body. Increasing levels of behavior, sensory experience, and learning. II. Developmental Processes A. The first developmental process is cell division, known as mitosis. Within 12 hours after fertilization, the zygote divides into two equal parts. B. The second, which occurs during the embryonic period, is cell migration, the movement of newly formed cells away from their point of origin. C. The third is cell differentiation. Initially, all of the embryo’s cells, or embryonic stem cells, are equivalent and interchangeable. After several cell divisions, they start to specialize in terms of structure and function. D. The fourth developmental process is selective death of certain cells. This cell suicide is known as apoptosis. E. Hormones also play a role in prenatal development. 1. The presence or absence of androgens causes development to proceed one way or the other. a. The presence of it causes male sex organs to develop. b. The absence of it causes female genitalia to develop. III. Early Development A. Phylogenic continuity is the idea that because of our common evolutionary history, humans share many characteristics, behaviors, and developmental processes with other animals, especially mammals. B. By the 4 day after conception, the cells arrange themselves into a hollow sphere with a bulge of cells, called the inner cell mass, on one side. 1. Identical twins result from a splitting in half of the inner cell mass 2. Fraternal twins result when two eggs are released from the ovary and both are fertilized. C. By the end of the 1 week, implantation occurs, in which the zygote embeds itself in the uterine lining and becomes dependent on the mother for sustenance. D. After implantation, the embedded wall of cells starts to differentiate. 1. The inner cell mass becomes the embryo a. During the 2 nd week, it folds itself into 3 layers. i. The top layer becomes the nervous system, nails, teeth, inner ear, lens of the eyes, and outer surface of skin ii. The middle layer becomes muscles, bones, the circulatory system, inner layers of the skin, and other internal organs iii. The bottom layer develops into the digestive system, lungs, urinary tract, and glands 2. The rest become an elaborate support system, including the amniotic sac and placenta, that enables the embryo to develop. 3. A few days after the embryo differentiates into 3 layers, a U-shaped groove forms down the center of the top layer. The folds at the top of the groove fuse, creating the neural tube. a. One end will swell and develop into the brain b. The rest will become the spinal cord E. The amniotic sac is a transparent, fluid-filled membrane that surrounds and protects the fetus. 1. Because the amniotic fluid keeps the fetus afloat, it can exercise its muscles unhampered by gravity. F. The placenta is a support organ that permits the exchange of materials carried in the bloodstreams of the fetus and the mother. It is a rich network of blood vessels. 1. Blood vessels running from the placenta to the embryo and back again are contained in the umbilical cord. 2. The placenta prevents the fetus’s and mother’s blood from mixing. 3. Oxygen, nutrients, minerals, and antibodies are transported to the placenta by the mother’s circulating blood. They then cross the placenta and enter the fetal blood system. 4. Waste products cross the placenta in the opposite direction and are removed by the mother’s excretory processes. 5. The placenta also produces hormones a. Estrogen increases the flow of maternal blood to the uterus b. Progesterone suppresses uterine contractions that could lead to premature birth. IV. An Illustrated Summary of Prenatal Development A. Earlier development takes place at a more rapid pace than later development and areas nearer the head develop earlier than those farther away, a tendency known as cephalocaudal development. B. At 4 weeks: 1. The embryo is curved so tightly that the head and tail- like structure are almost touching 2. A primitive heart is already eating and circulating blood 3. Arm and leg buds are present C. At 5½ weeks: 1. The nose, mouth, and palate begin to differentiate into separate structures. 2. 3 weeks later, the nose and mouth are almost fully formed 3. Cleft palate originates sometime between 5½ and 8 weeks. D. At 9 weeks: 1. Rudimentary eyes and ears are forming. 2. All internal organs are present, although most undergo further development 3. Sexual differentiation starts 4. Ribs are visible, fingers and toes have emerged, and nails are growing 5. The fetus makes spontaneous movements, but the mother cannot feel them. E. At 11 weeks: 1. The heart has achieved its basic adult structure 2. Developing spine and ribs, as well as divisions of the brain, are visible. F. At 16 weeks: 1. Fetus is capable of intense kicks, felt as a mild “flutter.” 2. External genitalia are developed and gender is revealed G. At 18 weeks: 1. Fetus begins to suck its thumb 2. Fetus is covered with fine hair, and a greasy coating protects its skin H. At 20 weeks: 1. Fetus spends more time in a head-down position 2. Components of facial expressions are present –fetus can raise eyebrows, wrinkle forehead, and move mouth. 3. Amniotic sac becomes more cramped, leading to a decrease in fetal movement I. At 28 weeks: 1. Brain and lungs are sufficiently developed 2. Eyes can open and move (especially during REM sleep). 3. Auditory system is now functioning and the fetus hears and reacts to sounds V. Fetal Behavior A. Movement 1. From 5 or 6 weeks after conception, the fetus moves spontaneously, starting with a simple bending of the head and spine that is followed by increasingly complex movements. 2. The fetus also moves its limbs, wiggles its fingers, grasps the umbilical cord, moves its head and eyes, and yawns 3. Some fetuses are usually very active, while others are more sedentary a. This prenatal continuity extends into the postnatal period b. More active fetuses turn out to be more active infants. 4. An important form of fetal movement is swallowing a. The fetus drinks amniotic fluid, which passes through its gastrointestinal system b. This promotes the normal development of the palate 5. At about 10 weeks, the fetus exercises its lungs through “fetal breathing,” moving its chest wall in and out. B. Behavioral Cycles 1. Once the fetus begins to move at 5 or 6 weeks, it is in almost constant motion for the next month. 2. Rest-activity cycles, bursts of high activity alternating with little or no activity for minutes at a time, emerge as early as 10 weeks. 3. Daily circadian rhythms also become apparent, with less activity in the early morning and more in the late evening. VI. Fetal Experience A. Sight and Touch 1. The visual experience of the fetus is minimal 2. The fetus does, however, experience tactile stimulation from its activity. a. In the course of moving, its hand come into contact with other body parts b. As it grows larger, the fetus bumps against the walls of the uterus c. By full term, they respond to maternal movements, suggesting their vestibular system is functional. B. Taste 1. The amniotic fluid contains a variety of flavors that the fetus can detect and favor over others. C. Smell 1. Amniotic fluid takes on odors from what the mother has eaten. 2. Smells can be transmitted through liquid, and amniotic fluid comes into contact with the fetus’s odor receptors through fetal breathing, providing fetuses with the opportunity to smell. D. Hearing 1. External sounds, such as voices of people, are audible to the fetus 2. The prenatal environment includes many maternal bodily sounds 3. The fetus responds to sounds from the 6 month on. a. During the last trimester, external noises elicit changes in movement and heart rate. VII. Fetal Learning A. Habituation is a simple form of learning that involves a decrease in response to repeated or continued stimulation 1. This decreased response is evidence of learning and memory. B. Newborns remember the scent of the amniotic fluid they lived in. 1. They develop a preference for the food their mother ate while they were in the womb. C. They also remember sounds they heard in the womb 1. They prefer to listen to their own mother’s voice Chapter 2: Prenatal/Teratogens (pgs 56-66) I. Environmental Influences A. A teratogen is an external agent that can cause damage or death during prenatal development 1. A crucial factor in the severity of the effects of teratogens is timing. 2. The sensitivity period is the period of time during which a developing organism is most sensitive to the effects of external factors; when the fetus is maximally sensitive to the harm of teratogens. 3. Thalidomide was prescribed to treat morning sickness in the 60s. Mothers who took it gave birth to babies with major limb deformities. a. Serious defects occurred only if the woman took the drug between the 4 and 6 week after conception B. A crucial factor influencing the severity of teratogenic effects is the amount and length of exposure. 1. Most have a dose-response relation, a relation in which the effect of exposure to an element increases with the extent of exposure. C. Experiences during the prenatal period program the physiological set points that will govern physiology in adulthood. 1. This is referred to as fetal programming. D. Effects of teratogens can also vary according to individual differences in genetic susceptibility. E. Face Up To Wake Up 1. Sudden infant death syndrome (SIDS) is the sudden, unexpected death of an infant less than 1 year of age that has no identifiable cause. 2. The most common SIDS scenario is putting a baby to bed and finding it dead in the morning a. This may be due to an inadequate reflexive response to respiratory occlusion (suffocating on a pillow/blanket). 3. There are several steps to reduce the risk of SIDS a. Putting infants to sleep on their back b. Parents should not smoke c. Babies should sleep on a firm mattress with no pillow d. Infants should not be wrapped in lots of blankets or clothes e. Infants who are breastfed are less likely to die of SIDS F. Legal Drugs 1. Because the use of these substances is a life style choice, their effects are particularly wide-spread 2. Cigarettes a. When a pregnant woman smokes, she gets less oxygen, and so does her fetus b. The fetuses of smokers metabolize some of the carcinogens in tobacco. c. The main developmental consequences are slowed fetal growth and low birth weight. d. 1 in 10 women smoke during pregnancy 3. Alcohol a. “The most common human teratogen.” b. The leading cause of fetal brain injury. c. Between ’05 and ’10, 7.6% of women drank during pregnancy. d. Women who use alcohol before pregnancy are most likely to use alcohol during. e. When a pregnant woman drinks, the alcohol in her blood crosses the placenta into both the fetus’s bloodstream and the amniotic fluid. i. A fetus has less ability to metabolize and remove alcohol from its blood, so it remains there longer ii. Immediate behavioral effects include altered activity levels and abnormal startle reflexes. f. Maternal drinking can result in fetal alcohol spectrum disorder (FASD). Effects include: i. Facial deformities ii. Mental retardation iii. Attention problems iv. Hyperactivity G. Illegal Drugs 1. Almost all commonly abused illegal drugs have been shown to be, or are suspected of being dangerous for prenatal development a. It is difficult to pin down how dangerous particular drugs are because pregnant women who use one illegal substance often abuse others as well. 2. Prenatal exposure to marijuana affects: a. Memory b. Learning c. Visual skills 3. Cocaine effects: a. Fetal growth retardation b. Premature birth c. Impaired ability to regulate arousal and attention d. Newborns born to coke-addicted mothers have to go through withdrawal. e. Persistent cognitive and social deficits H. Environmental Pollutants 1. The bodies of most Americans contain a mix of toxic metals, synthetic hormones, and various ingredients of plastics, pesticides, and herbicides that can be teratogenic. I. Occupational Hazards 1. Many women have jobs that bring them into contact with a variety of environmental elements that are potentially hazardous to prenatal development. II. Maternal Factors A. Age 1. Infants born to girls 15 years or younger are 3-4 times more likely to die than those born to mothers 23-29. 2. Older mothers are at a greater risk for many negative outcomes for themselves and their fetus, including fetal chromosomal abnormalities and birth complications. B. Nutrition 1. If a pregnant woman has an inadequate diet, her child may also be nutritionally deprived. a. Newborns who received inadequate nutrients while in the womb tend to have smaller brains containing fewer brain cells 2. Because malnutrition is common in impoverished families, it often coincides with the host of other risk factors, making it difficult to isolate its effects on prenatal development. C. Disease 1. STDs are hazardous to the fetus a. If the infant comes into contact with active herpes in the birth canal, blindness or even death can result b. HIV is sometimes passed to the fetus in the womb 2. Maternal illness may also affect the development of psychopathology. a. The incidence of schizophrenia is higher for those whose mothers had the flu during the first trimester D. Maternal Emotional State 1. A woman’s emotions can affect her fetus a. The fetuses of women who reported higher levels of stress were more physically active throughout their gestation The Newborn/Prematurity Chapter 2: pgs 70-81 I. State of Arousal A. State refers to a level of arousal and engagement in the environment, ranging from deep sleep to intense activity. B. Sleep 1. On average, newborns sleep twice as much as young adults 2. REM sleep, characterized by quick, jerky eye movements under closed lids, is an active sleep state a. Constitutes 50% of a newborns total sleep time. b. Researchers believes it helps with vision development 3. Non-REM sleep is a quiet sleep state characterized by the absence of motor activity or eye movements and more regular brain waves, breathing and heart rate. 4. Napping newborns may actually be learning while asleep because their brains do not become disconnected from external stimulation. 5. Newborns generally cycle between sleep and waking states several times in a 24-hour period. C. Crying 1. Infants cry for many reasons including illness, pain, and hunger 2. In times of hardship, such as famine, cranky babies have been known to be more likely to survive because their distress elicits adult attention. 3. Newborn’s cries are differentially shaped by the sounds of the language in their environment. D. Soothing 1. Many effective soothing techniques involve holding, rocking, and talking or singing to relieve an infant’s distress. 2. Swaddling is a soothing technique involving wrapping a baby tightly in cloths or a blanket 3. Touch can have a soothing effect on infants E. Response to Distress 1. If a parent responds quickly to severe distress but delays responding to minor upset, the infant may learn to cope with less serious problems on their own and end up crying less F. Colic 1. Some infants are prone to excessive, inconsolable crying for no apparent reason, a condition referred to as colic. 2. They tend to have high-pitched, unpleasant cries 3. The causes of colic are unknown but 1 in 10 US infants suffer from it II. Negative Outcomes At Birth A. Infant Mortality 1. Infant mortality, death during the first year of birth, is now relatively rare. (About 6.14 in 1000) B. Low Birth Weight 1. The average newborn in the US weighs 7.5 lbs. Infants below 5.5 lbs are considered low birth weight (LBW). 2. Some LBW infants are premature, any child born at 35 weeks after conception or earlier. 3. Others are referred to as small for gestational age, those who weigh substantially less than normal based on weeks since conception 4. Slightly more than 8% of US newborns are LBW. 5. LBW newborns have a heightened level of medical complications: a. Higher rates of neurosensory deficits b. More frequent illness c. Lower IQ scores d. Lower educational achievement. 6. Very LBW babies (less than 3.3 lbs) are particularly vulnerable 7. Causes include: a. Teratogens b. The skyrocketing rate of a twin 8. Long-Term Outcomes a. Children who were LBW infants have a higher incidence of developmental problems i. The lower their birth weight, the more likely they are to have persistent difficulties. b. They suffer from higher levels of hearing, language, and cognitive impairments. c. In preschool and elementary school, they are more likely to be distractible and hyperactive and have learning disabilities. d. More likely to experience social problems e. Adolescents who were LBW are less likely than their siblings to complete high school. 9. Intervention Programs a. A research study shows that touch is a vital part of a newborns life b. Field developed a therapy that involves massaging LBW babies and flexing their arms and legs. c. LBW babies who receive this therapy are more active and alter and gain weight faster than those who don’t C. Multiple-Risk Model 1. Risk factors tend to occur together 2. A negative developmental outcome is more likely when there are multiple risk factors. D. Poverty as a Developmental Hazard 1. All other factors like malnutrition, illness, stress, cigarette smoking, etc. are more likely to be experience by a woman in poverty 2. LBW infants have lower eventual developmental outcome in poverty than in middle class. E. Risk and Resilience 1. Developmental resilience is successful development in spite of multiple and seemingly overwhelming developmental hazards Genetics/Individual Differences: Chapter 3 pgs 84-106 I. Genetic and Environmental Forces A. Researchers have mapped the entire genome, the complete set of genes, of myriad species of plants and animals 1. Humans have around 21,000 genes B. Development results from the close and continual interplay of nature and nurture C. There are three key elements of the model of hereditary and environmental influences 1. The genotype is the genetic material an individual inherits 2. The phenotype are the observable expression of the genotype, including both body characteristics and behavior 3. The environment is every aspect of the individual and his or her surroundings (including prenatal experience) other than the genes themselves. D. Genetic and Environmental Forces 1. Parent’s Genotype – Child’s Genotype a. The transmission of genetic material (chromosomes and genes) from parent to offspring b. The nucleus of every cell contains chromosomes, long threadlike molecules made up of two twisted strands of DNA, which carries all the biochemical instructions “packaged” in genes. i. Each gene is a segment of DNA that is the code for the production of particular proteins ii. Genes affect development and behavior only through the manufacture of proteins c. Researchers have discovered that genes make up only about 2% of the human genome i. Much of the rest of our genome turns out to play a supporting role in influencing genetic transmission by regulating the activity of protein-coding genes d. Human Heredity i. Humans normally have a total of 46 chromosomes. ii. Each chromosome pair carries, usually at corresponding locations, genes of the same type. iii. Every individual has two copies of each gene. e. Sex Determination i. The sex chromosomes determine an individual’s sex ii. Females have two X chromosomes and males have one X and one Y chromosome. iii. It is the presence of a Y chromosome that makes an individual male iv. A gene on the Y chromosome encodes the protein that triggers the prenatal formation of testes by activating genes on other chromosomes. v. The testes produce the hormone testosterone, which takes over the molding of maleness f. Diversity and Individuality i. Genes guarantee that humans will be similar to one another in certain ways, both at the species level and the individual level. They also guarantee differences at both levels. ii. Mutations are changes that occur in a section of DNA. iii. Some mutations are random, others are caused by environmental factors iv. Some mutations increase viability, providing the basis for evolution. v. The random assortment of chromosomes creates variability vi. Further variation is introduced by crossing over 2. Child’s Genotype – Child’s Phenotype a. The relation between one’s genotype and one’s phenotype b. Although every cell in your body contains copies of all the genes you received from your parents, only some of those genes are expressed. i. Some genes are active, while others are not c. Gene Expression: Developmental Changes i. Genes influence development and behavior only when they are turned on, and human development proceeds normally only if genes get switched on and off in the right place, at the right time, and for the right length of time. ii. The switching on and off of genes is controlled primarily by regulator genes. iii. Genes never function in isolation; they belong to extensive networks in which the expression of one gene is a precondition for the expression of another, and so on. iv. External factors can affect the switching on and off of genes, such as the effect of thalidomide on limb development. v. The fact that regulator genes can repeatedly switch other genes on and off in different patterns means that a give gene can function multiple times in multiple places during development vi. This results in enormous diversity in genetic expression d. Gene Expression: Dominance Patterns i. About one-third of human genes have two or more different forms, known as alleles. ii. The alleles of a given gene influence the same trait or characteristic but contribute to different developmental outcomes iii. Some genes have only two alleles, one dominant and one recessive. iv. A person can inherit two of the same allele and be homozygous or two different alleles and be heterozygous. v. The dominant-recessive pattern of inheritance pertains to relatively few human traits as well as to a large number of genetic disorders. vi. A single gene can affect multiple traits vii. Both alleles can be fully expressed or blended in heterozygotes viii. Some genes are expressed differently, depending on whether they are inherited from the mother or from the father. ix. Polygenic inheritance is where several different genes contribute to any give phenotypic outcome 3. Child’s Environment – Child’s Phenotype a. The impact of the environment on the child’s phenotype b. The child’s observable characteristics result from the interaction between environmental factors and the child’s genetic makeup c. Because of the continuous interaction of genotype and environment, a given genotype will develop differently in different environments. i. This idea is expressed by the concept of the norm of reaction, which refers to all the phenotypes that could theoretically result from a given genotype in relation to all the environments in which it could survive/develop ii. A child with a given genotype would develop differently in a loving family than they would in an abusive family. d. Examples of Genotype – Environment Interaction i. Phenylketonuria (PKU) is a disorder related to a defective recessive gene on chromosome 12 ii. Affected individuals can’t metabolize phenylalanine iii. This given genotype results in quite different phenotypes depending on environmental circumstances. iv. There is a combination of environmental and genetic factors leading to antisocial outcomes v. Suffering abusive treatment as a child and possessing a particular variant of MAOA have a higher incidence of antisocial behavior e. Parental Contributions to the Child’s Environment i. Parents’ behavior toward their children is genetically influenced 4. Child’s Phenotype – Child’s Environment a. This restates the active child theme, the child as a source of his or her own development b. Children are active creators of the environment in which they live in two important ways: i. By virtue of their nature and behavior, they actively evoke certain kinds of responses from others ii. By actively selecting surroundings and experiences that match their interests, talents, and personality characteristics. c. Beginning in the preschool years, children’s friendship opportunities increasingly depend on their own characteristics, as they choose playmates and pals with whom they feel compatible d. As they gain more autonomy, they increasingly select aspects of the environment that fit their temperament and abilities. 5. Child’s Environment – Child’s Genotype a. Although the structure of DNA remains fixed, certain epigenetic mechanisms can alter the functioning of genes and create stable changes in their expression i. This helps to explain why identical twins do not have identical pathways through life: different environments can alter gene expression in subtle ways across developmental time b. Changes in gene expression that are mediated by the environment involve processes of methylation, which silence gene expression i. The greater the differences in the twins’ lifestyle and experiences, the greater the differences in their methylation levels. c. The myriad risk factors associated with growing up in poverty appear to act on developing children via epigenetic processes i. Adults who grew up in impoverished households exhibit different patterns of gene expression decades later than adults who grew up in high- SES homes 6. The complexity of gene – environment relationships raises both challenges and opportunities for developmental scientists a. Challenge: The genome can no longer comfortably be considered immutable irrespective of the widely varying environments in which children develop b. Opportunity: As this field continues to develop, it may become possible to determine which aspects of the environment are most likely to have a lasting impact on children’s eventual health and well-being. II. Behavior Genetics A. Behavior genetics is concerned with how variation in behavior and development results from the interaction of genetic and environmental factors 1. “Why are people different from one another?” B. All behavioral traits are heritable, influenced to some degree by hereditary factors 1. Polygenic traits are affected by the combination of many genes 2. Multifactorial genes are affected by a host of environmental factor as well as genetic ones C. Two premises underlie the endeavor to tease apart genetic and environmental contributions to the differences observed among a population 1. To the extent that genetic factors are important for a given trait or behavior, individuals who are genotypically similar should be phenotypically similar 2. To the extent that shared environmental factors are important, individuals who were reared together should be more similar than people who were reared apart D. Behavior Genetic Research Designs 1. Behavior geneticists compare how high the correlations of a trait are among individuals who vary in the degree to which they are genetically related a. They compare the resulting correlations to see if they are: i. Higher for more closely related individuals ii. Higher for individuals who share the same environment b. The twin-study design compares the correlations for identical twins with those for same-sex fraternal twins i. Identical twins are 100% genetically similar ii. Fraternal twins are 50% c. With different levels of genetic similarity and essentially equal environmental similarity, the difference between the correlations for the two types of twins is treated as an index of the importance of genetic factors. d. The adoption study examines whether adopted children’s scores on a given measure are correlated more highly with those of their biological parents and siblings. i. Genetic influences are inferred to the extent that children resemble their biological relatives more than they do their adoptive ones e. The adoptive twin study compares identical twins that grew up together versus apart. i. If the correlations for twins reared apart are similar to together, it suggests that environmental factors have little effect 2. Family Studies of Intelligence a. Genetic influence is shown by generally higher correlations for higher degrees of genetic similarity i. Identical twins resemble one another in IQ more than do fraternal twins. b. Environmental influences are reflected in the fact that identical twins are not identical in terms of IQ. c. As twins get older, the degree of variance in IQ accounted for by the genetic similarity increase. d. E. Heritability 1. To estimate how much of the variability in measures of a given trait is attributable to genetic and environmental factors, heritability estimates are derived 2. Heritability is a statistical estimate of how much the measured variance on a trait among individuals in a given population is attributable to genetic differences among those individuals a. Heritability estimates tell us nothing about the relative contributions of genetic and environmental factors to the development of an individual b. They estimate how much of the variation among a given population of people is due to the differences in their genes. 3. Genes do nothing more than code for proteins, so they affect behavior only as those proteins affect the processes involved in behavior 4. High heritability does not imply immutability a. The fact that a trait is highly heritable does not mean that there is little point in trying to improve the course of development related to that trait. F. Environmental Effects 1. Every examination of genetic contributions to behavior and development is also a study of environmental influences a. Estimating heritability automatically estimates the proportion of variance not attributable to genes b. Behavior geneticists try to asses the extent to which aspects of an environment shared by biologically related people make them more alike or different i. Growing up in the same family 2. Behavior geneticists’ investigations of the effects of non- shared environments arise from the recognition that even children who grow up in the same family do not have all their experiences in common. a. Siblings may experience their parents’ behavior toward them differently b. They may be affected differently by the divorce of their parents. c. Siblings may be highly motivated to differentiate themselves from one another 3. Siblings themselves are an important part of the environment, and each provides different experiences for the others. 4. The primary effect of non-shared environmental factors is to increase the differences among family members Brain and Body Development: Chapter 3 pgs 106-127 I. Structures of The Brain A. Fundamental to all aspects of behavioral development is the development of the CNS and brain B. Neurons 1. The basic units of the brain’s remarkably powerful informational system are its more than 100 billion neurons that constitute the gray matter of the brain 2. Neurons are specialized for sending and receiving messages between the brain and all parts of the body and brain a. Sensory neurons transmit information from sensory receptors that detect stimuli in the external environment or within the body itself b. Motor neurons transmit information from the brain to muscles and glands c. Interneurons act as intermediaries between the two 3. All neurons are made up of three main components: a. The cell body contains the basic biological material that keeps the neuron functioning b. The dendrites are fibers that receive input from other cells and conduct it toward the cell body in the form of electrical impulses c. The axon is a fiber that conducts electrical signals away from the cell body to connections with other neurons 4. Neurons communicate with one another at synapses, which are microscopic junctions between the axon terminal of one and the dendritic branches of another. a. Electrical and chemical messages cross synapses and cause the receiving neurons either to fire, or to be inhibited from firing. C. Glial Cells 1. Glial cells are the brain’s white matter, and make up nearly half of the brain a. They form the myelin sheath around axons, which insulates them and increases the speed and efficiency of information transmission b. Severe consequences can arise from disorders that affect myelin i. Multiple sclerosis is a disease in which the immune system attacks myelin, interfering with neuronal signaling and producing varying degrees of physical and cognitive impairment 2. Glial cells play a further role in communication within the brain by influencing the formation and strengthening of synapses 3. Glial cells also communicate biochemically among themselves in a network separate from the neural network D. The Cortex 1. The cerebral cortex is considered the “most human part of the brain” and constitutes 80% of it. 2. The folds and fissures form during development as the brain grows within the confined space of the skull a. These convolutions make it possible to pack more cortex into the limited space. 3. The cortex plays a primary role in a wide variety of mental functions depending on which of the lobes, the major areas of the cortex a. The occipital lobe is involved in processing visual information b. The temporal lobe is associated with memory, visual recognition, speech and language, and the processing of emotion and auditory information c. The parietal lobe is important for spatial processing. It’s also involved in the integration of information from different sensory modalities, and it plays a role in integrating sensory input with information stored in memory d. The frontal lobe is involved in cognitive control, including working memory, planning, decision-making, and inhibitory control. e. Information from multiple sensory systems is processed and integrated in the association areas that lie in between the major sensory and motor areas 4. Complex mental functions are mediated by multiple areas of the brain, with an extraordinary degree of interactivity both within and across brain regions 5. Cerebral Lateralization a. The cortex is divided into two separate halves, or cerebral hemispheres. b. Sensory input from one side of the body goes to the opposite side of the brain, and the motor areas of the cortex control movements of the opposite side of the body c. The left and right hemispheres communicate with each other by way of the corpus callosum, a dense tract of nerve fibers that connect them d. The two hemispheres are specialized for different modes of processing, a phenomenon called cerebral lateralization. II. Developmental Processes A. Neurogenesis and Neuron Development 1. Neurogenesis is the proliferation of neurons through cell division a. It is virtually complete by about 18 weeks after conception b. We continue to generate new neurons throughout life i. During bouts of learning, neurogenesis occurs in the hippocampus. c. It can be inhibited by stress, which suggests that it isn’t fixed and predetermined; it is adaptive, increasing under rewarding conditions and decreasing in threatening environments. 2. After “birth” neurons begin migration to their ultimate destinations 3. Once they reach them, cell growth and differentiation occur a. Neurons first grow an axon and then a bush of dendrites b. They then take on the specific structural and functional characteristics of the different structures of the brain c. Axons elongate as they grow toward specific targets d. Dendrites go through arborization, an enormous increase in the size and complexity of the dendrite tree that results from growth, branching, and the formation of spines on the branches. i. This increases the dendrites’ capacity to form connections with other neurons. 4. The process of myelination, the formation of the insulating myelin sheath around some axons, begins in the brain before birth and continues into early adulthood. a. It begins deep in the brain, beginning with the brainstem, and moves upward and outward into the cortex at a fairly steady rate. b. The various cortical areas become myelinated at different rates B. Synaptogenesis 1. In synaptogenesis, each neuron forms synapses with thousands of others, resulting in the formation of the trillions of connections 2. Both the timing and rate of synapse production vary for different cortical areas C. Synapse Elimination 1. The explosive generation of neurons and synapses during synaptogenesis results in a huge surplus of neural connections 2. As a consequence of this hyperconnectivity, newborns may experience synesthesia, the blending of different types of sensory input 3. Approximately 40% gets eliminated in synaptic pruning. a. It happens at different times in different areas of the brain III. The Importance of Experience A. Experience plays a central role in which of the brain’s synapses will be pruned and which will be maintained 1. “Use it or lose it” 2. Those synapses that are frequently activated are selectively preserved 3. The more often a synapse is activated, the stronger the connection becomes between the neurons involved 4. “Neurons that fire together wire together.” B. The capacity of the brain to be molded or changed by experience, plasticity, means that less information needs to be encoded in the genes. 1. The number of genes involved in the formation and functioning of the nervous system is enough to specify only a very small fraction of the normal complement of neurons and neural connections. C. The collaboration between nature and nurture in building the brain occurs differently for two kinds of plasticity 1. One kind involves the general experiences that almost all infants have 2. The second involves specific, idiosyncratic experiences that children have as a result of circumstance. D. Experience – Expectant Processes 1. The role of general human experience in shaping brain development is experience – expectant plasticity. a. According to this view, the normal wiring of the brain is in part a result of the kinds of general experiences that have been present throughout human evolution, experiences that every human will have b. Thus, our experience of the external world plays a fundamental role in shaping the most basic aspects of structure. 2. Benefits and Downsides: a. Benefit: Because experience helps shape the brain, fewer genes need to be dedicated to normal development b. Benefit: The brain is better able to recover form injury to certain areas, because other brain areas can take over the function that would have been performed by the damaged area c. Downside: It is accompanied by vulnerability 3. When an expected form of sensory experience is absent, such areas can become at least partially reorganized to serve some other function. 4. Sensitive Periods a. A key element in experience – expectant plasticity is timing i. There are a few sensitive periods when the human brain is especially sensitive to particular kinds of external stimuli ii. The neural organization that does(n’t) occur during sensitive periods is typically irreversible. E. Experience – Dependent Processes 1. The brain is sculpted by idiosyncratic experience through experience – dependent plasticity. a. Neural connections are created and reorganized constantly as a function of an individual’s experiences. 2. The brains of rats that grow up in complex environments have more dendritic spines on their cortical neurons, more synapses per neuron, and more synapses overall. a. Because of this, they perform better in a variety of learning tasks 3. Rats that are trained to use just one forelimb to get a reward have increased dendritic material in the particular area of the motor cortex that controls the movement of the trained limb. IV. Brain Damage and Recovery A. Because of its plasticity, the brain can become rewired after suffering damage B. Children who suffer from brain damage have a better chance of recovering lost function than adults 1. This is because after the damage has occurred, other areas of the immature brain can take over function 2. Adults who sustain the same type of brain damage undergo no reorganization of lost function and may have permanent loss. C. Likelihood of recovery depends on how extensive the damage is and what aspect of brain development is occurring at the time of damage. D. Even when children appear to have made a full recovery from an early brain injury, deficits may emerge later. 1. Behavior that appears normal early in development may deteriorate. E. The worst time to suffer brain damage is very early, during prenatal development and the first year after birth, when neurogenesis is occurring and basic brain structures are forming 1. Damage at this point may have cascading effects on subsequent aspects of brain development F. When brain damage is sustained in early childhood, the chance for the brain’s rewiring itself and recover lost function are best. V. Growth and Maturation A. The Body grows and develops for 20% of the human life span 1. We get 3 times taller and 15-20 times heavier between birth and age 20. 2. The most rapid growth occurs in the first 2 years and in early adolescence. a. Girls experience their adolescent growth spurt before boys i. Boys experience theirs about 2 years after the girls, permanently passing them in both height and weight. b. Full height is ac
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