Dev. Psych Chapter Notes 1,2,3-2 PDF

Developmental Psych Chapter Notes Chapter 1: Reasons to learn about child development - Learning about child development is valuable for many reasons: - It can help us become better parents and more empathetic caregivers and service providers for children - Inform our views about soci...

Developmental Psych Chapter Notes Chapter 1: Reasons to learn about child development - Learning about child development is valuable for many reasons: - It can help us become better parents and more empathetic caregivers and service providers for children - Inform our views about social issues that affect children - Improve our understanding of human nature Enduring themes in child development 1. Nature and Nurture: How do nature and nurture together shape development? - Every aspect of development, from the most specific behaviour to the most general trait, reflects people’s biological endowment (their nature) as well as the experiences that they have had (their nurture) - Nature refers to our biological endowment, in particular, the genes we receive from our parents. This genetic inheritance influences every aspect of our makeup, from broad characteristics such as physical appearance, personality, intellect, and mental health to specific preferences, such as political attitudes and propensity for thrill-seeking - Nurture refers to the wide range of environments, both physical and social, that influence our development, including the womb in which we spend the prenatal period, the homes in which we grow up, the schools that we attend, the broader communities in which we live, and the many people with whom we interact - Genome: each person’s complete set of hereditary information influences behaviours and experiences, behaviours and experiences influence the genome - Epigenetics: the study of stable changes in gene expression that are mediated by the environment - Evidence for the enduring epigenetic impact of early experiences and behaviours comes from research on methylation, a biochemical process that reduces expression of a variety of genes and is involved in regulating reactions to stress 2. The active child: how do children shape their own development? - Even infants and young children actively contribute to their own development through their patterns of attention, use of language, and choices of activities - Children play by themselves for the sheer joy of doing so, but they also learn a great deal in the process. - Older children’s play, which typically is more organized and rule-bound than the play of younger children, promotes additional useful capabilities, such as the self-control needed for turn-taking, adhering to rules, and controlling one’s emotions in the face of setbacks. 3. continuity/discontinuity: in what ways is development continuous and in what ways is it discontinuous? - Many developments can appear either continuous or discontinuous, depending on how often and how closely we look at them - Continuous development: the idea that changes with age occur gradually, in small increments, like that of a pine tree growing taller and taller - Discontinuous development: the idea that changes with age include occasional large shifts, like the transition from caterpillar to cocoon to butterfly 4. Mechanisms of change: how does change occur? - The mechanisms that produce developmental changes involve a complex interplay amongst experiences, genes, and brain structures and activities - One particularly interesting analysis of mechanisms of development change involves the roles of brain activity, genes, and learning experiences in the development of effortful attention - Effortful attention involves voluntary control of one’s emotions and thoughts. It includes processes such as inhibiting impulses (e.g. obeying requests to put all of one’s toys away, as opposed to putting some away but then getting distracted and playing with the remaining ones); controlling emotions (e.g. not crying when failing to get one’s way); and focusing attention (e.g. concentrating on one’s homework despite the inviting sounds of other children playing outside). - Difficulty in exerting effortful attention is associated with behavioural problems, weak math, and reading skills, and mental illness - These studies have shown that when people are controlling thoughts and emotions, brain activity is especially intense in connections between the limbic area–a part of the brain that plays a large role in emotional reactions– and the anterior cingulate and prefrontal cortex brain structures involved in setting and attending to goals - Connections amongst these brain areas develop considerably during childhood, and their development appears to be one mechanism that underlies improving effortful attention during childhood. - Specific genes have been found to influence the production of key neurotransmitters–chemicals involved in communication amongst brain cells. Variations in these genes amongst children are associated with variations in the quality of performance on tasks that require effortful attention. 5. The sociocultural context: how does the sociocultural context influence development? - The contexts that shape development include the people with whom children interact directly, such as family and friends; the institutions in which they participate, such as schools and religious organizations; and societal beliefs and values, such as those related to race, ethnicity, and social class  - Sociocultural context: the physical, social, cultural, political, economic, and historical circumstances that make up any child’s environment - Cross-cultural comparisons often reveal that practices that are rare or nonexistent in one culture are common in others. - In modern multicultural societies, many contextual differences are related to ethnicity, race, and socioeconomic status (SES) – a measure of social class that is based on income and education. - Virtually all aspects of children’s lives– from the food they eat to the parental discipline they receives to the games they play– very with ethnicity, race and SES - Children in lower-income families are also more likely than children from higher-income families to grow up in lone-parent homes or to be raised by neither biological parent. - The accumulation of these disadvantages over years of development, often termed cumulative risk, seems to be the greatest obstacle to poor children’s successful development. 6. Individual differences: how do children become so different from one another? - Individual differences, even amongst siblings, reflect differences in children’s genes, in their treatment by other people, in their interpretations of their own experiences, and in their choices of environment - 1. Differences in genetics - 2. Differences in treatment by parents and others - 3. Differences in reactions to similar experiences - 4. Differences in choices of environments 7. Research and children’s welfare: how can research promote children’s well-being? - Principles, findings, and methods from child development research are being applied to improve the quality of children’s lives Methods for studying child development The scientific method The use of the scientific method involves 4 basic steps: - Choosing a question to be answered - Formulating a hypothesis regarding the question - Developing a method for testing the hypothesis - Using the resulting data to draw a conclusion regarding the hypothesis - For a measure to be useful, it must be directly relevant to the hypothesis being tested, reliable and valid. - Reliability means that independent observations of a given behaviour are consistent - Interrater reliability: the amount of agreement in the observations of different raters who witness the same behaviour - Test-retest reliability: the degree of similarity of a participant’s performance on 2 or more occasions - Validity means that a measure assesses what it is intended to measure - Internal validity: the degree to which effects observed within experiments can be attributed to the factor that the researcher is testing - External validity: the degree to which results can be generalized beyond the particulars of the research - Replication, which combines properties of reliability and validity, is the degree to which subsequent experiments, using the same procedures but with different people, will yield the same results as the original experiment. - In recent years, the “replicability crisis”, which describes the low percentage of findings that can be replicable, has prompted scientists working in various fields, including psychology, to adopt measures to increase methodological vigour and encourage collaboration. - Amongst the main situations used to gather data about children are interviews, naturalistic observation, and structured observation. - Interviews are especially useful for revealing children’s subjective experiences. - Naturalistic observation is particularly useful when the primary goal is to describe how children behave in their everyday environments. - Structured observation is most useful when the main goal is to describe how different children react to an identical situation - Correlation does not imply causation. The 2 differ in that correlations indicate the degree to which 2 variables are associated, whereas causation indicates that changing the value of 1 variable will change the value of the other. - Direction-of-causation problem: the concept that a correlation between 2 variables does not indicate which, if either, variable is the cause of other other - Third-variable problem: the concept that a correlation between 2 variables may stem from both being influenced by some third variable - Independent variable: the experience that participants in the experimental group receive and that those in the control group do not receive. - Dependent variable: a behaviour that is measured to determine whether it is affected by exposure to the independent variable - Correlational designs are especially useful when the goal is to describe relations amongst variables or when the variables of interest cannot be manipulated because of technical or practical considerations - Experimental designs are especially valuable for revealing the causes of children’s behaviour - Data about development can be obtained through cross-sectional designs (examining different children of different ages), through longitudinal designs (examining the same children at different ages), or through microgenetic designs (presenting the same children with repeated relevant  experiences over a relatively short period and analyzing the change process in detail) - It is vital for researchers to adhere to high ethical standards. Amongst the most important ethical principles are striving to ensure that the research does not harm children physically or psychologically; obtaining informed consent from parents and, where possible, from children; preserving participants’ anonymity; and correcting any inaccurate impressions that children form during the study. Chapter 2: Trimester Weeks Major Milestones 1 1 Zygote travels from fallopian tube to womb and embeds in uterine lining; cells arrange into a ball and begin to form embryo and support system. Embryo forms three layers, which will become the 2-3 nervous system and skin; muscles, bones, and circulatory system; and digestive system, lungs, and glands; neural tube also develops. 4 Neural tube continues to develop into the brain and spinal cord; primitive heart is visible, as are leg and arm buds. 5-9 Facial features differentiate; rapid brain growth occurs; internal organs form; fingers and toes emerge; sexual differentiation has started. 10-24 Heart develops its basic adult structures; spine and ribs develop more fully; brain forms major divisions. 2 13-24 Lower body growth accelerates; external genitalia are fully developed; body develops hairy outer covering; fetus can make basic facial expressions; fetal movements can be felt by the pregnant parent. 3 25-38 Fetus triples in size; brain and lungs are sufficiently developed at 28 weeks to allow survival outside of womb; visual and auditory systems are functional; fetus is capable of learning and behaviours begin to emerge. Conception - Epigenesis: the emergence of new structures and functions in the course of development - Gametes (germ cells): reproductive cells -egg and sperm- that contain only half the genetic material of all the other cells in the body - Meiosis: cell division that produces gametes - 23 pairs of chromosomes, 23 from each parent - Conception: the union of an egg and sperm - Zygote: a fertilized egg cell Developmental Processes 1. Cell division (mitosis): within 12 hours after conception, the zygote divides into 2 parts each containing a full complement of genetic material. Divides multiple times. Through continued cell division over the course of 38 weeks, the zygote consists of trillions of cells 2. Cell migration: the movement of newly formed cells away from their point of origin. Amongst the many cells that migrate are the neurons that originate deep inside the embryonic brain and then travel to the outer reaches of the developing brain 3. Cell differentiation: embryonic stem cells can develop into any type of body cell→ the cell’s location influences its future development via the chemical and cell-to-cell contact with neighbouring cells, and gene expression -which genes are switched on- distinguishes one type of cell from another 4. “Cell suicide”: apoptosis is genetically programmed cell death, readily apparent in hand development: the formation of fingers depends on the death of the cells in between the ridges in the hand plate. Aptosis has been referred to as a “ticking death timer” because it follows a specific timeline, programmed into cells themselves. - Hormones have a major influence throughout prenatal development. For example, hormones play a crucial role in sexual differentiation. - All fetuses have the potential to develop male or female genitalia, androgens, a class of hormones that includes testosterone, leads to the development of male genitalia. If androgens are absent, female genitalia develop. - A rare genetic syndrome known as “congenital adrenal hyperplasia” (CAH), the adrenal gland overproduces androgens during delta development. Genetic females (2X chromosomes) with CAH may develop masculinized genitalia along with working ovaries and a uterus. - Glucosteroids limit fetal growth and help fetal tissues mature - Towards the end of gestation, fetus increases the production of hormones for the maturation of key organs for life outside the womb Early Development - By the 4th day after conception, the cells arrange themselves into a hollow sphere with a bulge of cells, called the “inner cell mass” on one side. - Identical (monozygotic) twins result from a splitting in half of the inner mass cell, they have exactly the same genetic makeup - Fraternal (dizygotic) twins result when 2 eggs happen to be released from the ovary into the fallopian tube and both are fertilized - Because they originate from 2 different egg cells and 2 different sperm, fraternal twins are no more alike genetically than non-twin siblings - Ectopic pregnancy: pregnancy in which the fertilized egg implants and grows in an organ outside of the uterus (most often in a fallopian tube), preventing normal growth and putting the pregnant person at risk of injury or death - Occur in roughly 2 % of all pregnancies - As cells start to differentiate, the inner cell mass becomes the embryo and the rest of the cells become a support system including the amniotic sac and placenta that enable the embryo to develop - During the 2nd week, the inner cell mass folds itself into 3 lakers each with a different developmental destiny: - The top layer becomes the nervous system, the nails, teeth, the inner ear, the lens of the eyes, and the outer surface of the skin - The middle layer becomes muscles, bones, the circulatory system, the inner layers of the skin, and other internal organs - The bottom layer develops into the digestive system, lungs, urinary tract, and glands - After the embryo has differentiated into these 3 layers, a U-shaped groove forms down the centre of the top layer, the folds at the top of the groove move together and fuse, creating the neural tube→ One end of the neural tube will swell and develop into the brain, and the rest will become the spinal cord - The amniotic sac is a membrane filled with a clear, watery fluid in which the fetus floats, operates as a protective buffer providing it with a relatively even temperature and cushioning it against jolting. - The placenta is a support organ for the fetus; it keeps the circulatory systems of the fetus and pregnant person separate, but a semipermeable membrane permits the exchange of some materials between them, oxygen and nutrients from pregnant parent to the fetus; waste and carbon dioxide from fetus to pregnant parent - Acts as a barrier from dangerous bacteria and toxins - The amniotic sac is connected to the placenta via the umbilical cord, which is a tube containing the blood vessels that run to the fetus Summary of Prenatal Development - Cephalocaudal development: the pattern of growth in which areas near the head develop earlier than areas farther from the head - At 4 weeks: embryo is curved tightly, the primitive heart is seen and beating circulating blood; arm and leg buds seen - At 5 ½ weeks: nose, mouth, and palate begin to form and differentiate; cleft palate, a malformation of this area can originate sometime between 5 ½ and 8 weeks - At 9 weeks: rapid brain growth, eyes and ears are forming, all internal organs are present, sexual differentiation has started, ribs are visible, fingers and toes have emerged, nails are growing - At 11 weeks: the heart achieves basic adult structure, developing spine and ribs, major divisions of the brain - During last 5 months: growth of the lower body accelerates, external genitalia are substantially developed visible sex organs - 18-week old fetus is covered with fine hair and a greasy coating protects its skin, components of facial expressions present-fetus can raise its eyebrows, wrinkle its forehead, and move its mouth - 28 weeks: brain and lungs are sufficiently developed for survival on their own, and eyes can open and move especially during REM sleep. The auditory system is functioning and the fetus reacts to sounds - During the last 3 months: the fetus grows dramatically, essentially tripling its weight, develops a wide repertoire of behaviours and learns from experiences Fetal Experience and Behaviour - Prenatal experiences shape the developing fetus- nature and nurture - The fetus participates in and contributes to its own development- an active child - Despite very different environments (discontinuity), fetuses and children show surprising similarities (continuity) Movement - From 5-6 weeks after conception, the fetus moves spontaneously - Earlies movement emerges at around 7 weeks: hiccups - Hiccups are a burping reflex preparing the fetus for eventual nursing by removing air from the stomach - Fetuses swallow amniotic fluid which is excreted back into the amniotic sac - Tongue movements with swallowing promote the development of the palate - Passage of amniotic fluid helps the digestive system mature - 10 weeks: fetal breathing– takes in small amounts of amniotic fluid and expels it → initially infrequent but becomes more stable Touch - Fetuses have been observed not only grasping their umbilical cords but also rubbing their faces and sucking their thumbs - Fetuses’ choice of thumb to suck predicts later handedness  - Right thumb→ right-handed; left thumb→ left-handed Sight - Fetuses can process visual information by the third trimester of pregnancy - Fetuses have visual preferences; fetuses prefer light displays that are top-heavy (resembling correctly oriented faces) over bottom-heavy (resembling inverted faces) Taste - The amniotic fluid contains a variety of flavours, and fetuses like some better than others→ the fetus has a sweet tooth Smell - Amniotic fluid takes on odours from what the pregnant parent has eaten - Smells can be transmitted through liquid, and amniotic fluid comes into contact with the fetus’s odour receptors through fetal breathing, providing fetuses with the opportunity for olfactory experience - Prenatal scent learning plays an important role in many species’ early developmental processes - Phylogenetic continuity: humans share many characteristics and developmental processes with nonhuman animals due to our shared evolutionary history - Nurture begins prenatally: experiences before birth play an important role in postnatal developmental processes Hearing - The noise level in the uterus ranges from about 70-95 decibels - The pregnant parents’ voice is particularly prominent the fetus hears it and its heart rate changes - During the third trimester; external noises elicit changes in fetal movements and heart rate as well. - Infants exposed to womb sounds had larger auditory cortexes- the sounds that fetuses typically hear during gestation may facilitate brain development - Because sound is such a prevalent feature of the fetal environment, it plays a major role in prenatal learning Fetal learning - Fetuses grow bored if a stimulus is repeated over and over again. This process is called habituation: a decrease in response to repeated or continued stimulation - Habituation provides evidence of learning and memory: the stimulus loses its novelty only if the stimulus is remembered from one presentation to the next  - When a perceptible change in the stimulus occurs, it becomes interesting again– a process called dishabituation. - Fetuses as young as 30 weeks show habituation to both auditory and visual stimuli indicating that their CNS are developed for learning and short-term memory to occur - Fetuses also learn from the tastes and smells that they encounter in the womb Hazards to Prenatal Development - The most common is spontaneous abortion also known as miscarriage; most miscarriages occur very early in pregnancy - The majority of embryos that are miscarried very early have severe defects such as a missing chromosome or an extra one. - 25-50% of pregnant parents experience at least 1 miscarriage - Approximately 1% of pregnant parents experience recurrent miscarriages, or the loss of 3 or more consecutive pregnancies Teratogens - Teratogens are a vast number of environmental agents that have the potential to harm a fetus - Many teratogens cause damage only if they are present during a sensitive period in prenatal development; the major organ systems are most vulnerable to damage at the time when their basic structures are being formed, because the timing is different for each system, and sensitive periods are different for each system. - Another crucial factor influencing the severity of teratogenic effects is the amount and duration of exposure. - Most teratogens show a dose-response relation: the greater the fetus’s exposure to a potential teratogen, the more likely it is that the fetus will suffer damage and the more severe any damage is likely to be. - Teratogens frequently occur in combination, making it difficult to separate out their effects– the presence of multiple risk factors can have a cumulative impact on development - Negative effects of prenatal experience may not be immediately evident; fetal programming refers to the belated emergence of effects of prenatal experience that help determine physiology in adulthood. - For example: during ww2 pregnant women faced malnutrition, fetus adjusts its metabolism and these adjustments did not reset themselves - The effects of teratogens can also vary according to the individual differences in genetic susceptibility in both the pregnant parent and fetus, certain substances that aren’t dangerous to most people, are dangerous to those susceptible to them - Identifying teratogens is further complicated by the existence of the sleeper effect, in which the impact of a given agent may not be apparent for many years Drugs  - Almost all drugs, legal and illegal, have been shown to be dangerous to prenatal development - Any drugs should be taken under the supervision of a physician - Accutane is a known teratogen and those taking it are urged to comply with contraceptive measures and ongoing pregnancy testing Antidepressants - Antidepressant medications raise particularly challenging issues for people contemplating becoming pregnant - These medications are hugely beneficial to those with depression and treatment of depression during pregnancy helps reduce post-partum depression which affects 10-30% of people who have given birth - One potential solution is the use of non-pharmaceutical treatments for depression which pregnant parents say they prefer - Behavioural interventions including CBT, mindfulness-based cognitive therapy that help treat perinatal depression Opioids - Opioid medications mimic the effects of neurotransmitters which means they have the potential to wreak havoc on the developing brain - Opioids can be highly dangerous to fetuses - Neonatal abstinence syndrome (NAS) is a form of drug withdrawal seen when fetuses exposed to opioids in the womb are born - Common effects of NAS include low birth weight, problems with breathing and feeding, and seizures - Treatments for these fetuses include methadone or morphine to help with withdrawals Cannabis - Effects of cannabis on fetuses are inconclusive, the combination of cannabis and tobacco is particularly dangerous - Prenatal exposure to cannabis is associated with a range of problems involving attention, impulsivity, learning and memory in older children The 2 drugs that cause the most widespread damage to fetal development are cigarettes (nicotine) and alcohol Cigarette smoking - Smoking causes both the pregnant smoker and the fetus to get less oxygen - Fetuses metabolize some of the cancer-causing agents contained in tobacco - Secondhand smoke has an indirect effect on fetal oxygen as well, through the pregnant parent’s intake of smoke when someone is smoking nearby - The main developmental consequences of smoking while pregnant are slowed fetal growth and low birth weight and increased risk of miscarriage  - Linked with an increased risk of sudden infant death syndrome (SIDS) and a variety of other problems including lower IQ, ADHD, and cancer. - Greater smoking intensity predicts worse outcomes, including stillbirths - The effects of smoking are greatest early in gestation - E-cigarettes avoid some of the issues related to smoke exposure but the use of nicotine in any from is still a risk for fetal development and can affect fetal cardiac, respiratory, and nervous systems Alcohol - Alcohol use during pregnancy is the leading cause of fetal brain injury and is generally considered to be the most preventable cause. - Rates are highest in Europe and Ireland, and lowest in the Middle East - Data suggest that alcohol use during pregnancy reflects broader cultural views about the use of alcohol, especially by women - When a pregnant person drinks, the alcohol is their blood crosses the placenta into the fetus’s bloodstream and amniotic fluid. The fetus gets alcohol directly - The fetus has less ability to metabolize and remove alcohol from its blood, so it remains in the fetus’s system longer - Prenatal exposure to alcohol can result in fetal alcohol spectrum disorder (FASD), which comes with multiple birth defects - One frequently observed symptom of FASD is a set of facial structures like the eyes, nose, and lips - Other forms of FASD can include intellectual development disorder, attention challenges, and hyperactivity - Even moderate drinking during pregnancy such as one drink per day can have both short-term and long-term negative effects on development. - The negative effects can include low birth weight, increased risk for ADHD, and delays in cognitive development and school achievement Environmental Pollutants - The bodies and bloodstreams of most Americans contain a noxious mix of toxic metals, synthetic hormones, and various ingredients of plastics, pesticides, and herbicides that can be teratogenic → these substances often have significant negative effects on the fetus - Air pollution from the burning of fossil fuels is associated with low birth weight and neurotoxicity and disproportionately affects low-income populations, different forms of pollution act in combination - Rapid industrialization can lead to pollution-related negative effects on fetuses - New potential teratogens are still being discovered, nano plastics, tiny plastic particles that are ubiquitous in single-use packaging, were detected in the human placenta in 2021 Maternal factors - Age, nutritional status, health and stress level Age - Infants born to teenagers who are 15 or younger are 3-4 times more likely to die before their 1st birthday than those born to young adults - Higher pregnancy and mortality rates may be related to social and cultural factors such as pressure to marry young, lack of access to contraceptives, and sexual violence - There is a dose-response relationship with the risk of negative outcomes for both parent and fetus increasing with maternal age→ children born to older parents are at heightened risk for developmental disorders such as autism - The causal pathways linking each parent to their infants’ developmental outcomes are likely different since only the pregnant parent contributes to prenatal environments and birth circumstances Nutrition - The fetus depends on the pregnant parent for all its nutritional requirements, an inadequate supply of specific nutrients can have dramatic consequences - For example, pregnant parents who get too little folic acid (Vitamin b) are at high risk for having an infant with a neural tube defect such as spina bifida - Because malnutrition is more common in low-income families, it often coincides with a host of other risk factors - Individuals who had experienced malnutrition as fetuses showed impaired performance on attentional tasks and had prematurely aged brains Disease - Although most illnesses that occur during pregnancy have no impact on the fetus, some do - For example, if contracted early in pregnancy, rubella can have a wide-ranging developmental effect, including deafness, blindness and intellectual developmental disorders - Sexually transmitted infections (STIs) are also quite hazardous to the fetus; cytomegalovirus (CMV), a type of herpes that is present in around 55% of women of reproductive age in Canada, is the most common infection passed from pregnant parent to fetus - CMV can damage the fetus’s CNS and cause a variety of other serious defects, including hearing loss. - Genital herpes can also be very dangerous. If the infant comes into contact with active herpes lesions in the birth canal, blindness or even death can result. - HIV is sometimes passed to the fetus in the womb or during birth, but the majority do not become infected themselves. While it can also be transmitted through breastmilk, the milk contains a carbohydrate that may actually protect from HIV - Zika virus can cause microcephaly and stunted brain growth because it affects cortical-neural progenitor cells Maternal Emotional State  - Stress during pregnancy can affect development from cognitive development to later psychiatric diagnoses - Maternal prenatal depression was associated with changes in brain structure in children ages 2-5, a primary mechanism for these effects is alternations in the HPA axis and the hormone cortisol, a glucosteroid which helps regulate stress in both the pregnant parent and the fetus - Glucosteroids slow the growth of the fetus - The concept of fetal programming suggests that the altered hormonal environment for the fetus may lead to long-term changes in how children and adults cope with stress via disrupted HPA axis functioning - Pregnant parents from ethnic and racial minorities experience more stress than those from majority ethnic groups, this stress becomes worse in less wealthy countries - The strongest predictor of later outcomes is child anxiety - The increased popularity of prenatal yoga and meditation classes suggests that there may be straightforward ways to reduce at least some aspects of pregnancy-related stress with potential benefits for both the pregnant parent and fetus State of Arousal - State refers to a continuum of arousal, ranging from deep sleep to intense activity. - The 2 newborn states that are of particular concern to parents, sleeping and crying, have been studied extensively Sleep - 2 facts about sleep and its development are of particular importance: - 1. The average newborn sleeps twice as much as young adults do - 2. The pattern of 2 different sleep states, REM sleep and non-REM sleep, changes dramatically with age - Rapid eye movement (REM) sleep is an active sleep state associated with dreaming in adults; it is characterized by quick, jerky eye movements under closed lids, a distinctive pattern of brain activity, body movements, and irregular heart rate and breathing. - Non-REM sleep is a quiet sleep state characterized by the absence of motor activity or eye movements and more regular, slow brain waves, breathing, and heart rate - REM sleep constitutes fully 50% of a newborn’s total sleep time - The proportion of REM sleep declines rapidly to only 20% by 3-4 and remains low for the rest of life - Because newborns spend so much time asleep they don’t have much opportunity to amass waking visual experiences, REM sleep helps to make up for the natural deprivation of visual stimulation, facilitating the early development of the visual system in both the fetus and newborn  - REM sleep may be adaptive for neonates is that the natural jerking movements “Myoclonic twitching” that occur during REM sleep give infants the opportunity to build sensorimotor maps - Neonates’ slumbering brains do not become disconnected from external stimulation to the same extent that the brains of older individuals do. - Nighttime awakenings typically diminish over the course of the first postnatal year - There can be a mismatch between the circadian rhythm of the person expressing milk and the infant drinking the milk, impacting sleep. Because of hormones such as melatonin are present in breastmilk Crying - Rather than diminishing over the first few months, as parents expect, it actually increases, peaking around 6-8 weeks of age - Crying behaviour tends to decrease in frequency around 3-4 months of age, potentially because infants now have somewhat more control over their environment - Shaken baby syndrome can result in severe head trauma or death Soothing - One very common technique is swaddling, which involves wrapping the baby tightly in cloths or a blanket, restricting limb movement. - The tight wrapping provides a constant high level of tactile stimulation and warmth Colic - A condition where some infants are prone to excessive, inconsolable crying for no apparent reason during the first few months of life - The causes are unknown and may include allergic responses to the breast-feeding parent’s diet, formula intolerance, immature gut development, or excessive gassiness - Affects 18% of Canadian infants - Ends by about 3 months of age and has no long-term effects - The best option for parents is to seek social support which can relieve stress and frustration Negative Outcomes at Birth - Neonatal caregivers worldwide use an evaluation tool called the APGAR score to quickly assess the health of newborn infants immediately following birth - A cumulative score is derived from rating of the skin, pulse, facial responses, arm and leg activity, and breathing strength - Perfect scores are rare; the worst result is the death of an infant - A much more common negative outcome is low birth weight, which can have long-term consequences Infant mortality  - Infant mortality-death during the first year after birth- is now relatively rare in the industrialized world - Reasons having to do with limited access to health care, a greater prevalence of macrosomic births (very large babies) and higher rates of poverty Low Birth Weight - Infants who weigh less than 2500 grams (5 ½ pounds) at birth are considered to be of LBW. - Many LBW infants are premature, or preterm, that is they are born before 37 weeks of gestation. - Other LBW infants are referred to as small for gestational age: they may be either preterm or full-term but they weigh substantially less than normal for their gestational age - LBW newborns have a heightened level of medical complications, higher rates of neurosensory deficits, frequent illness, and lower educational achievement. - Very LBW babies, those who weigh less than 1500 grams or 3.3 pounds are particularly vulnerable - There are numerous causes of LBW and prematurity, including smoking, alcohol, and environmental pollutants such as lead and mercury Long-term outcomes - Children who were LBW infants have a higher incidence of developmental problems such as sensory impairments, poorer academic achievement, and more behaviour problems - Studies suggest links between VLBW and childhood psychiatric issues, ADHD, autism, and anxiety - The hypothesized pathways between LBW and these negative outcomes include white-matter reduction, ventricular enlargement, and other abnormal brain development outcomes - The strongest predictor of outcomes for VLBW infants is maternal education - The majority of LBW children’s negative effects gradually diminish and generally end up within the normal range on most developmental measures Intervention programs - Interventions that educate caregivers and parents on childcare of their LBW infants have yielded numerous positive effects such as improved behavioural outcomes, greater weight gain, higher IQs etc. compared to their LBW peers - The more risks the infant endures the lower the chances of a good outcome Multiple Risk Models - A pregnant person who engages in substance abuse is also likely to be under a great deal of stress and unlikely to eat well, take vitamins, seek prenatal care, or have a strong social support network  - The cumulative effects of these prenatal risk factors will likely be compounded after birth if the parent’s unhealthy lifestyle persists - Heightened incidence of psychiatric problems in families with 4 or more risk factors - The more risk factors, the worse the potential outcomes - The outcome of pregnancy is less positive for infants or lower SES parents - Structural racism impacts fetal and newborn health - There are individuals faced with multiple overwhelming development hazards, even beginning before birth, who nevertheless do well. - Resilient children often have 2 factors in their favour: - 1. Certain personality characteristics, especially intelligence, responsiveness to others, and a sense of being capable of achieving their goals - 2. Responsive care from someone. Individual differences, and personal traits combined with a supportive environment can help us understand successes in the face of developmental challenges Chapter 3: Genetic and Environmental forces - Genome: the complete set of DNA of any organism, including all of its genes - Genotype: the genetic material an individual inherits - Phenotype: the observable expression of the genotype, including both body characteristics and behaviour - Environment: every aspect of individuals and their surroundings other than genes - These 3 elements are involved in 5 relations that are fundamental in the development of every child: - 1. Parents’ genetic contribution to children’s genotypes - 2. The contribution of children’s genotypes to their own phenotypes - 3. The contribution of children’s environments to their phenotypes - 4. The influence of children’s phenotypes on their environments - 5. The influence of children’s environments on their genotypes Parents’ genotype-Child’s genotype - Involves the transmission of genetic material from parent to offspring - The nucleus of every cell in the body contains chromosomes, long threadlike molecules made up of 2 twisted strands of DNA (deoxyribonucleic acid). - DNA carries all the biochemical instructions involved in the formation and functioning of an organism. - These instructions are packaged into “genes” the basic unit of heredity in all living things - Genes affect development and behaviour only through the manufacture of proteins Human Heredity - Humans have a total of 46 chromosomes, 23 pairs  - Each chromosome pair carries, usually at corresponding locations, genes of the same type– that is, a sequence of DNA that is relevant to the same traits. - Because each parent passes along one chromosome to their offspring, every individual has 2 copies of each gene. Genetic Diversity and Individual Differences 1. One mechanism that promotes variability amongst individuals is the random assortment of chromosomes in the formation of egg and sperm - During gamete division, the 23 pairs of chromosomes are shuffled randomly, chance determining which member of each pair goes into each new egg or sperm. - The odds are essentially zero that any 2 individuals, even those related, will have the same genotype, aside from identical twins - A further variation is introduced by a process called “crossing over”: when gametes divide, the 2 members of a pair of chromosomes sometimes swap sections of DNA - As a result, some of the chromosomes that parents pass on to their offspring are constituted differently from their own. 2. A second mechanism that enhances variability is mutation, a change in a section of DNA. Some mutations are random, spontaneous errors; others are caused by environmental factors - Most mutations are harmful - Occasionally, a mutation enhances the individual’s genetic fitness by increasing disease resistance or allowing the individual to adapt to some crucial aspect of the environment - Individuals with the favourable mutated gene are more likely to survive long enough to produce offspring and pass the mutated gene onto their offspring heightened chances of survival - Across generations, these favourable genes proliferate in the gene pool of the species Sex Determination - The sex chromosomes are an exception to the general pattern of chromosome pairs - Female = 2 large X chromosomes (XX) - Male = 1 large X chromosome and 1 smaller Y chromosome (XY) - The genetically male parent always determines the sex of the offspring: - If an X-bearing sperm fertilizes an egg, a female (XX) zygote results - If a Y-bearing sperm fertilizes an egg, a male (XY) zygote results - A gene on the Y chromosome encodes the protein that triggers the prenatal formation of testes by activating genes on other chromosomes, triggering the production of the hormone testosterone - Sex chromosomes are one of several primary and secondary characteristics in the spectrum of biological sexual variance, and the “sex” referring to this biological spectrum is distinct from “gender” which refers to social and cultural attributes associated with a person’s identity Child’s Genotype-Child’s Phenotype - Phenotypes include both physical characteristics, such as height and eye colour, and behavioural characteristics, such as temperament and intelligence - Genes also influence unobservable, intermediate aspects of the phenotype that impact behaviour, most notably, our brain and nervous systems. These intermediate phenotypes are known as “endophenotypes” and mediate the pathways between genes and behaviour - Although every cell in your body contains copies of all the genes you received from your parents, only some of those genes are expressed. - Some genes are active while others are not Gene expression: Developmental Changes - The switching on and off of genes is controlled primarily by “regulator genes” - The switching on and off of one gene is always part of a chain of genetic events: when one gene is switched on, it causes another gene to turn on or off, which has an impact on the status of other genes. - 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. - External factors also affect the switching on and off of genes - Example: the effect of thalidomide on limb development in which the sedative interferes with the functioning of genes underpinning normal growth factors - Another example: early visual experience is necessary for the normal development of the visual system because it causes the switching on of certain genes which switch on other genes in the visual cortex, the ramifications of decreased visual experience are observed in cases of children with cataracts Gene Expression: Dominance Patterns - One-third of human genes have 2 or more different forms, known as “alleles” - The alleles of a given gene influence the same trait or characteristic (eye colour) but they contribute to different developmental outcomes (brown, blue, hazel eyes etc) - The simplest pattern of gene expression: dominant-recessive pattern: - Some genes have only 2 alleles, one of which is dominant and the other recessive. - There are 2 possibilities: - 1. A person can inherit 2 of the same allele–2 dominant or 2 recessive–and homozygous for the trait in question  - 2. The person can inherit 2 different alles–1 dominant and 1 recessive–and be heterozygous for the trait. - When an individual is homozygous, the corresponding trait will be expressed - When an individual is heterozygous, the dominant allele will be expressed. - The X chromosome carries roughly 1500 genes whereas the Y chromosome carries about 200 - When a female child inherits a recessive allele on the X chromosome from mother, she is likely to have a dominant allele on the X chromosome from her father to suppress it so she will not express the trait - When a male child inherits a recessive allele on the X chromosome from his mother, he will likely not have a dominant allele from his father to suppress it so he will express the trait - Genetically male people are more likely than genetically female people to suffer a variety of sex-linked inherited disorders caused by recessive alleles on their X chromosome - Inheritance patterns are more complicated for most traits ranging from physical characteristics such as height and weight to psychological constructs such as aggression and temperament - Polygenic inheritance pattern: many different genes contribute to any given phenotypic outcome - More than 500 genes contribute to individual differences in human intelligence, a polygenic trait that is not determined by any single gene Child’s Environment-Child’s Phenotype - Because of the continuous interaction of genotype and environment, a given genotype may develop differently in different environments - One example of a phenotype produced by a genotype-environment interaction is Phenylketonuria (PKU), a disorder related to a defective recessive gene or chromosome - Individuals who inherit this gene from both parents cannot metabolize phenylalanine, an amino acid present in many foods (especially red meats) and aspartame, an artificial sweetener. Phenylalanine accumulates in the bloodstream, causing impaired brain development and intellectual disabilities. - If infants with the PKU gene are kept on a stringent diet free of phenylalanine, intellectual impairment can be avoided - Thus, a given genotype results in very different phenotypes –intellectual development disorder or relatively normal intelligence– depending on environmental circumstances - A second example comes from the effects of abusive parents and how they interact with the child’s genotype to produce different adult outcomes. - Focused on the MAOA gene, an X-linked gene that inhibits brain chemicals associated with aggression.  - Young men who had a relatively inactive version of the MAOA gene, and who had experienced severe maltreatment, grew up to be more antisocial than other men who had also experienced severe maltreatment but who possessed a more active version of the MAOA gene. - 85% of the maltreated group with the relatively inactive gene developed some form of antisocial behaviour, and they were almost 10 times more likely to be convicted of a violent crime. - The higher incidence of antisocial behaviour was observed only for the group of boys who possessed both the genetic and environmental risk factors Parental Contributions to the Child’s Environment - Parents’ behaviour towards their children (e.g. how warm or reserved they are, how patient or short-fused) is genetically influenced, as are the kinds of preferences, activities, and resources to which they expose their children. - For example: parents for whom reading is challenging–perhaps related to genetic factors, such as reading disabilities like dyslexia, which are known to be highly heritable are less likely to provide a reading-oriented environment for their children than parents who are skilled readers - Researchers characterized the genotypes of cohabitating trios–a child and their 2 biological parents– and found that the child’s educational outcomes were predicted, in part, by parental alleles that the child did not inherit. - Non-transmitted parental alleles play an important role in the creation of the child’s environment, a phenomenon that the researchers describe as genetic nurture - By affecting the parents’ phenotypes (and thereby influencing the family environments), the parents’ genes affected their children’s educational success. Child’s Phenotype–Child’s Environment - 2 children, despite living in the same home with the same parents, experienced very different early environments by virtue of their own behaviours - Children also create their own environments by actively selecting surroundings and experiences that match their interests and personalities - As soon as infants start reaching, crawling and walking, they begin to select objects for exploration rather than relying on their parents’ choices of play objects Child’s Environment–Child’s Genotype - Epigenetics: the study of stable changes in gene expression that are mediated by the environment  - Epigenetic mechanisms, mediated by the environment, can alter the functioning of genes and create stable changes in their expression–and some of these changes can be passed onto the next generation - The epigenetic mechanism most commonly studied in humans is “methylation” which silences gene expression - Methyl molecules block transcription in the promoter region of the gene, turning off gene activity - DNA methylation typically operates like a dimmer switch, regulating the amount of protein produced by a given gene - Glucosteroids are involved in stress activity - Early stress affects methylation; children who experienced severe early-life stress in the form of child maltreatment show similar patterns of methylation in the glucocorticoid receptor gene - Study revealed epigenetic changes related to childhood abuse in the sperm of adult males– cells that are of particular interest as a possible mechanism for passing epigenetic changes from parent to child. Brain Development The Neuron - Neurons: cells that are specialized for sending and receiving messages between the brain and all parts of the body, as well as within the brain itself - Constitute the grey matter of the brain - Each neuron has 3 main parts: - Cell body: a component of the neuron that contains the basic biological material that keeps the neuron functioning - Dendrites: neural fibres that receive input from other cells and conduct it towards the cell body in the form of electrical impulses - Axons: neural fibres that conduct electrical signals away from the cell body to connect with other neurons - Neurons communicate by sending electrical and chemical signals across synapses - Synapses: microscopic junctions between the axon terminal of one neuron and the dendritic branches or cell body of another - Glial cells are another essential component of the brain, equal in numbers to neurons - Glial cells: cells in the brain that provide a variety of critical supportive functions - Glial cells perform a variety of critical functions, including the formation of a myelin sheath around axons, which increases the speed and efficiency of information transmission  - Myelin sheath: a fatty sheath that forms around certain axons in the body and increases the speed and efficiency of information transmission - function as neural stem and progenitor cells during prenatal brain development and some glial cells continue to do so into adulthood - When the brain is injured, some glial cells react by rapidly increasing in numbers, protecting the brain and potentially aiding in regeneration The Cortex - The cerebral cortex constitutes 80% of the human brain - The cortex includes 4 lobes, each associated with a specific set of behavioural characteristics - The occipital lobe: is primarily involved in processing visual information - The temporal lobe: is associated with speech and language and the processing of emotion and auditory information - The parietal lobe: engages in spatial processing and is also involved in the integration of information from different sensory modalities - The frontal lobe: the brain’s “executive”, is involved in cognitive control, working memory, planning, decision-making, and inhibitory control. - Information from multiple sensory systems is processed and integrated in the “association areas” that lie in between the major sensory and motor areas - The cortex is divided into 2 cerebral hemispheres - For the most part, 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 - The hemispheres communicate with each other primarily by way of the “corpus callosum”, a dense tract of connective nerve fibres between the 2 hemispheres. - The hemispheres are specialized for different modes of processing, a phenomenon referred to as “cerebral lateralization” which emerges early in human development - For example: young infants use their right hemispheres more than their left hemispheres to process faces and use their left hemispheres to process most aspects of speech - Contrary to popular belief; people aren’t left-brained or right-brained, and individuals do not tend to have a general preference for using one hemisphere over the other Developmental Processes Neurogenesis and Neuron Development  - Neurogenesis, the proliferation of neurons through cell division, begins 42 days after conception and is nearly complete by the midway point of gestation - Most of the roughly 100 billion neurons you currently possess have been with you since before you were born. - Humans continue to generate new neurons throughout life, particularly in the hippocampus–a brain area that is heavily involved in memory processes - After their “birth”, neurons migrate to their ultimate destinations–typically outwards from the centre of the brain towards the developing neocortex - Some neurons are pushed along passively by the newer cells formed after them, whereas others actively propel themselves toward their ultimate location - Once neurons reach their destination, they first grow an axon and then a bush of dendrites and take on the specific structural and functional characteristics of the different structures of the brain - Axons elongate as they grow toward their targets - The main change in dendrites is “arborization”--an enormous increase in the size and complexity of the dendritic “tree” that results from growth, branching, and the formation of “spines” on the branches - Arbourization increases the dendrites’ capacity to form connections with other neurons - As arborization allows neurons to grow in complexity over the several years of postnatal life, the cortex grows in surface area and the layers of the cortex become thicker - Myelination, the formation of the insulating myelin sheath around some axons, begins prenatally and continues into early adulthood. - The myelinated portions of axons are white, leading to the term “white matter”, and lie below the grey matter (cell bodies) at the surface of the cortex - Myelination begins deep in the brain and moves upwards and outwards into the cortex - This process occurs rapidly after birth, slows somewhat in toddlerhood and continues slowly into young adulthood - The various cortical areas become myelinated at very different rates, contributing to the different rates of maturation of different brain areas. Synaptogenesis - Each neuron forms synapses with thousands of others in a process called “synaptogenesis”, resulting in the formation of trillion connections - It begins prenatally and proceeds very rapidly both before birth and for some time afterwards. - Both the timing and rate of synapse production vary for different cortical areas; synapse generation is complete much earlier in the sensorimotor cortex, for example than in the frontal area.  - As with myelination, the differential timing of a synapse generation across areas of the brain likely contributes to the developmental timing of the onset of various abilities and behaviours Synapse Elimination - Approximately 40% of great synaptic superfluity is eliminated through synaptic pruning, which occurs at different times in different areas of the brain - The brain undergoes waves of synaptogenesis and synaptic pruning in the first months and years of life, but the brain also undergoes substantial changes during adolescence–measures of cortical thickness suggest that the outer layers of the cortex shrink at a faster rate during adolescence than during either childhood or early adulthood - The last area of the cortex to mature is the dorsolateral prefrontal cortex, which is vital for regulating attention, controlling impulses, foreseeing consequences, setting priorities, and other executive functions. - It does not reach adult dimensions until after the age of 20, and synaptic pruning continues until individuals are in their 30s. - Atypical patterns of pruning have been implicated in 2 developmental disorders: autism spectrum disorder (ASD) and schizophrenia - Autistic children have larger brains than neurotypical children and studies suggest that autistic children and adults have greater synaptic densities in some areas of their brains; increased cortical thickness in autistic children relative to neurotypical children, possibly indicating reduced or delayed rates of synaptic pruning - Neural connection in individuals with schizophrenia also follow an atypical trajectory and suggest excessive pruning in adolescence; the timing of the onset of schizophrenic symptoms in adolescence and young adulthood may be linked to aberrant pruning around puberty The Importance of Experience - Experience plays a central role in what is essentially a case of “use it or lose it” The more often a synapse is activated, the stronger the connection between the neurons involved: in short, neurons that fire together wire together - When a synapse is rarely active, it is likely to disappear: the axon of one neuron withdraws and the dendritic spine of the other is pruned away - Because of the brain’s capacity to be moulded or changed by the experience, referred to as “plasticity”, less information needs to be encoded in the genes - The plastic brain can recover from some forms on injury because other brain areas can take over the function that would have been performed by the damaged area - Children’s brains are more plastic than adults’ brains, children who sustain brain damage and have a better chance of recovering lost function than adults who sustain similar damage  - Adults who sustain the same type of brain damage undergo a minimal reorganization of language functions and may lose some language abilities permanently. - The collaboration between nature and nurture in building the brain occurs differently for 2 kinds of plasticity: - Experience-expectant plasticity involves the general experiences that almost all infants have just by virtue of being human - Experience-dependent plasticity involves specific, idiosyncratic experiences that children have as a result of their particular life circumstances such as growing up in Montreal or in the Amazon rainforest. Experience-Expectant Processes - Experience-Expectant plasticity: the process through which the normal wiring of the brain occurs in part as a result of species-typical experiences - The role of species-typical experience in shaping brain development is known as experience-expectant policy - Throughout human evolution, infants have experienced patterned visual stimulation, voices and other sounds, movement and manipulation, etc. The human brain can thus “expect” that these sources of experience will be available to fine-tune its circuitry–hence the term “experience-expectant” plasticity - The benefit of experience-expectant plasticity is that, because experience helps shape the brain, fewer genes need to be dedicated to normal development. - The downside is heightened vulnerability. If the experience that the developing brain “expects” does not occur, development may be compromised. Sensitive periods - As in other developmental processes, timing is a key element in experience-expectant plasticity. - During sensitive periods, the human brain is especially sensitive to specific external stimuli. - The neural organization that occurs (or does not occur) during sensitive periods is typically irreversible. - Adolescence, a time of rapid changes in the brain, may be a sensitive period for a range of cognitive and social processes Experience-Dependent Plasticity  - Experience-dependent plasticity: the process through which neural connections are created and reorganized throughout life as a function of an individual’s experiences - Neural connections are constantly being created and reorganized by our specific experiences in a process referred to as experience-dependent plasticity. - The brains of rats (and cats and monkeys) that grow up in richer environments have more dendritic spines on their cortical neurons, more synapses per neuron, and more synapses overall, as well as a generally thicker cortex and more of the supportive tissues (blood vessels and glial cells) that maximize neuronal and synaptic function. - Nonhuman animals reared in a complex environment (which is more akin to their natural environment) perform better in a variety of learning tasks than do their counterparts raised in bare cages - Training studies with humans reveal how highly specific experiences can shape the brain. Musicians provide a “natural experiment” in which some body parts are trained more intensely than others. The resulting evidence of plasticity mirrors nonhuman animal studies. - For example, adults who play wind instruments have thicker lip-related cortical areas than adults who do not play wind instruments. After years of practice, more cortical cells were devoted to controlling the lips of these skilled instrumentalists. - Another natural experiment comes from individuals who did not have the opportunity to learn a native language in childhood– for example, children who are born deaf and are not exposed to a sign language until they attend school or meet other deaf people who sign. - When tested as adults, deaf individuals who had had limited exposure to language as children showed less cortical thickness and grey-matter volume in brain areas related to language than deaf adults who were exposed to sign language early in life. LECTURE NOTES: LECTURE 1 Enduring themes: 1. Nature and Nurture - How do nature and nurture together shape development? - Nature (genome )= individual’s complete set of hereditary information - Nurture = environment (physical+social) - All human characteristics are created through the interaction of genes and environment - How does this interaction develop? - Our genome influences our behaviour and our development, genome and environment interact - Epigenetics = stable changes in gene expression that are mediated by the environment - Behaviours and experiences influence the genome by turning gene activity on or off - Do not actually change the genome; involve attachment of chemical compounds to it - Methylation = epigenetic mechanism that increases or decreases expression of genes - Differential susceptibility: different individuals respond to their environments in different ways → their genetic predisposition shapes the way they respond to their environment 2. Active Child - How do children shape their own development? - Children contribute to their own development starting in infancy and early childhood, and their contributions increase as they get older - 3 of the most important contributions during children’s first years are their: - 1. Attentional patterns: what do children attend to in their environments - 2. Use of language: how much do children speak, how complex is their speech, who they interact/speak with - 3. Play: how and who do they play with - Older children and adolescents have even more choices in their environments, friends, and activities; their choices can have a big effect on their future 3. Continuity/Discontinuity - In what ways is development continuous and in what ways is it discontinuous? - Continuous development: changes with age occur gradually, in small increments. Development occurs skill by skill and task by task - Discontinuous development: changes with age include occasional large shifts. Qualitative differences occur. Piaget, Freud, Erikson, and Kohlberg were stage theorists. - Piaget’s conservation of liquid quantity problem: - Children’s behaviour on this task is often used to exemplify the idea that development is discontinuous. - Do you know why? - Change in behaviour is viewed as a relatively sudden, qualitative change - Child has moved from one coherent way of experiencing the world to a different coherent way - Doesn’t seem to be a gradual shift - Depending on how it is viewed, changes in height can be viewed as either continuous or discontinuous 4. Mechanisms of Change - How does change occur? - Mechanisms = things that explain how some aspect of development occurs - Developmental mechanisms can be behavioural, neural, or genetic - The development of mathematical abilities could be explained by: - Improved strategies - Increased interconnection between the frontal cortex + intraparietal sulcus in the brain - The presence or absence of certain alleles 5. Sociocultural Context - How does the sociocultural context influence development? - Sociocultural context influences every aspect of children’s development - Bronfenbrenner: bioecological model - The most important component involves people with whom children interact - Institutions are influential and important  - Less tangible sociocultural factors include: historical era, economic structure, cultural beliefs, and cultural values 6. Individual Differences - How do children become so different from one another? - Scarr’s factors related to differences in children: - Genetic differences - Differences in treatments by parents and others - Differences in reactions to similar experiences - Different choices of environments 7. Research and Children’s Welfare - How can research promote children’s well-being? - Research often leads to a wide variety of benefits in diagnosing children’s problems and in helping children overcome them. - Anger-management programs - More valid child eye-witness testimony - Educational innovations Reasons to learn about child development: - Raising children - Child development research helps answer child-rearing questions - Example: helping children control their anger - In Canada, 25% of parents report spanking their children - Research suggests several effective alternatives: - Offering sympathy - Finding positive alternatives to expressing anger - Choosing social policies - Knowledge of child development facilitates informed decisions about social policy questions that affect children - Example: psychological research on children’s responses to leading interview questions can help courts obtain more accurate testimonies from preschool children - Understanding human nature - Child development research provides important to intriguing questions regarding human nature Research methods: Methods for studying child development: - The scientific method - Contexts for gathering data about children - Correlation and causation - Research designs for examining children’s development - Ethical issues in child development research The scientific method: - Approach to testing beliefs that involves: - Choosing a question to be answered - Formulating a hypothesis regarding the question - Developing a method for testing the hypothesis - Using the data yielded by the method to draw a conclusion regarding the hypothesis  - Key qualities of scientific measures/findings: - Reliability: degree to which independent measurements of a given behaviour are consistent - Validity: degree to which a test or experimental procedure measures what it intended to measure - Replicability: degree to which subsequent studies using the same procedures yield the same results as the original - Example: - Question: what abilities predict which children will be good readers? - Hypothesis: kindergartners who can identify the separate sounds within words will become better readers than those who cannot - Method: select group of kindergarteners, test their ability to separate sounds within words, then later test their reading skills, if hypothesis is proven then.. - Conclude: Kindergartener’s ability to identify sounds within words predicts later reading skill Contexts for Gathering Data about Children: - Interviews and Questionnaries: - Structured interviews: useful when goal is to collect self-reports on same topics from everyone being studied - Clinical interviews: useful for obtaining in-depth information about an individual child - Questionnaires: information gathered simultaneously through uniform set of questions presented to participants - Naturalistic observation: examining of ongoing behaviour in an environment not controlled by the researcher, useful for understanding everyday social interactions - Structured observation: method that presents identical situations to each child and records child’s behaviour Correlation and Causation: important goal of child development research; determine how variables are related to one another through: Associations, cause-effect relationships Variables= attributes that vary across individuals and situations - Correlational designs: demonstrated how 2 variables are related to eachother - Correlation: association, both variables change, can be positive or negative Correlation does NOT equal causation: - Cause-effect inference in correlation isn’t justified. Why? - Direction-of-causation problem: correlation between 2 variables doesn’t indicate whether each, if either, variable is the cause of the other - Third-variable problem: correlation between 2 variables may stem from both being influenced by some third variable Experimental Designs: a group of approaches that allow inferences about causes and effects to be drawn - Essential characteristics: - Random assignment of participants to group - Experimental control - Control group: group of participants that aren’t presented the experience of interest but in other ways are treated identically, e.g. kids taken to park and given NO icecream - Experimental group: group of participants who are presented the experience of interest, e.g kids taken to park and given lots of icecream - Experimental control refers to the ability of the researcher to determine the specific experiences that children have during the course of an experiment - Independent variable: icecream provided at park - Dependent variable: children’s happiness Research Designs for Examining Children’s Development: - Cross-sectonal design: compare children of different ages on a given behaviour or characteristic over a short period. - Longitudinal design: same children are studied twice or more of a substantial length of time, useful for revealing stability and change over time, - Microgenetic designs: same children are studied repeatedly over a short period, designed to provide in-depth depiction of processes that produce a change Code of ethical conduct: - Do no harm - Obtain informed consent - Preserve individual participant anonymity - Discuss with parents the relevant research information - Work to counteract unforeseen negative consequences - Correct inaccurate child impressions - Explain main finding at developmentally appropriate level LECTURE 2 Prenatal Development and Newborn Period Conception - Gametes (germ cells): reproductive cells (egg and sperm) that contain only half the genetic material of all other cells in the body. These are produced through a specialized cell division (meiosis). 23 Chromomes from both the mother and father lead to conception- 23 pairs of chromosomes - Conception: an egg and sperm unite; fertilization - Zygote: a fertilized cell Development processes: 4 development processes to transform Zygote→ Embryo (3-8 weeks) → Fetus (9 weeks-birth) - Mitosis: Cell division resulting in 2 identical daughter cells - Cell migration: newly formed cells move away from the point of origin - Cell differentiation: cells start to specialize in structure and function - Apoptosis: genetically programmed cell death Early development Support system for the embryo: - Amniotic sac: transparent, fluid-filled membrane that surrounds and protects the fetus - Placenta: support organ for the fetus that permits the exchange of materials carried in the bloodstreams of the fetus and mother - Umbilical cord: tube containing the blood vessels connecting the fetus and the placenta Neural tube formation - Neural tube: groove formed in the top layer of differentiated cells in the embryo that eventually becomes the brain and spinal cord Brain development is particularly dramatic before birth Fetal Experience and Behaviour - Movement: - Foetal movement starts 5-6 weeks after conception - Emergence of hiccups, swallowing - Movement of limbs, fingers  - Respiratory readiness for breathing independently after birth - Behaviour cycles: - Rest-activity cycles; less activity in the latter half in prenatal period - Circadian rhythm apparent - REM during active sleep - Sight: minimal; fetal preferences - Touch: contact with parts of the body; grasping umbilical cord, rubbing face, sucking thumb - Taste: can detect flavours in amniotic fluid - Smell: amniotic fluid takes on odour from what mother eats; phylogenetic continuity - Hearing: responds to various sounds from atleast 6 months Fetal Learning - Habituation: simple form of learning that involves a decrease in response to repeated or continued stimulation; seen at 30 weeks gestation in visual and auditory stimuli - Dishabituation: introduction of a new stimulus rekindles interest following habituation to a repeated stimulus. Response increases. Studies - 60 fetuses tested at term before birth - Played a poem through a loudspeaker above the mother’s abdomen - Half heard their mother reading the poem, other half heard a female stranger reading the poem - The fetal heart rate increased in response to the mother’s voice but decreased when hearing the stranger’s voice - Suggests that fetuses recognized their mother’s voice – which means they have learned and remembered what her voice sounds like - 40 newborns in Sweden and 40 in the USA were tested when they were about 33 hours old - They listened to vowel sounds that were either Swedish or English - If infants listened to their non-native language they sucked on their pacifier more than if they listened to their native language - Conclusion: the language that fetuses heard prenatally affected their perception of their native language → they LEARNED something about their native language Hazards to Prenatal Development Early development is a period of both opportunity and vulnerability - The properties that allow the fetus develop, learn from, and adapt to the environment it will soon encounter also leave it vulnerable to harm - Although environmental input is critical for shaping development (e.g. allowing to grow, learn, and adapt), harmful aspects of the environment can be detrimental to early development Sensitive periods of Prenatal Development - Teratogens: external agents that have the potential to cause harm during prenatal development - Sensitive period: developmental window during which a developing organism is most sensitive to the effects of external factors Teratogens - Potentially harmful agent - Individual differences in genetic susceptibility - Cumulative impact - Sleeper effect Dose-Response Relation - Potential problems depend on how much exposure to the teratogen is present and for how long - The more exposure, the more at risk the fetus becomes. Hazards to Prenatal Development Drugs: - Opioids (vicodin, percocet, oxycodone, fentanyl, heroin_ - Marijuana - Alcohol → fetal alcohol spectrum disorder (FASD) - Nicotine → sudden infant death syndrome (SIDS) - cigarette smoking, second hand smoke, e-cigarettes - Antidepressants (mixed evidence) Environmental Pollutants - Toxic metals, synthetic hormones, plastic ingredients, pesticides, herbicides, - Air and water pollution - Lead (dose-response relationship) Maternal Factors Age - Infant mortality rate is high for teen mothers age 15 or younger - Increased age into 30s and 40s also carries increased risk of infertility Nutrition - General malnutrition of mother affects growth of fetal brain; later cognitive impairments - Spina bifida, neural tube defects Disease - Rubella - STIs can damage CNS of fetus; CMV, genital herpes, HIV infections, AIDS - Infections, such as influenza may lead to schizophrenia - Zika virus can lead to microcephaly Maternal Emotional State - High maternal stress leads to increased stress hormone levels - Could lead to behaviour problems in children who were prenatally exposed to high levels of stress hormones - Fetal programming Maternal stress - The increased popularity of prenata yoga and meditation classes suggests that there may be straightforward ways to reduce at least some aspects of pregnancy-related stress Structual Factors - Structural racism in maternal and fetal health - According to the CDC, black mothers in the US die at 3-4x the rate of white mothers– they are 243% more likely to die from pregnancy or childbirth-related causes - Social inequities include differential access to: - Healthy food, clean water, safe neighborhoods, education, employment, reliable transportation, health insurance, high quality hospitals (due to historical segregation) - Health insurance: get prenatal care later and lose coverage sooner - Black mothers: - Face significantly higher rates of life-threatening complications - Are more likely to have chronic conditions (e.g. obesity, hypertension; as a result of social inequities described) - Face unconscious biases embedded in the medical system which affect their quality of care - About 50% more likely than white mothers to deliver prematurely - Twice as likely to experience maternal depression - Often factors like income and education are NOT protective  - Protective factors: primary caregiver (grandmother) → developmental resilience The Newborn Infant A healthy baby interacts with the environment right away - The active child - Explores and learns about new environment Exploration influenced by baby’s state of arousal - Active sleep - Quiet sleep - Crying - Active awake - Alert awake - Drowsing The Active child- State of Arousal Newborn States: - Western newborns: - Quiet sleep: 8 hours - Active sleep: 8 hours - Drowsing: 1 hour - Alert awake: 2.5 hours - Active awake: 2.5 hours - Crying: 2 hours - There are substantial individual and cultural differences in how much time babies spend in the different states Sleep - Newborns sleep twice as much as adults - Total sleep time declines regularly throughout childhood and more slowly throughout life - Rapid Eye Movement (REM) sleep: active sleep state; characterized by quick, jerky eye movements under closed eyelids; associated with dreaming in adults - Non-REM sleep: quiet or deep sleep state; characterized by absence of motor activity or eye movements; more regular, slower brain waves, breathing, and heart rate Crying - Infants cry to get attention of caregivers - Some reasons for crying include illness, pain, and hunger - Crying is normal behaviour - Peaks around 6-8 weeks or age and decreases around 3-4 months of age - Soothing: consoling crying baby - Swaddling: a soothing technique, used in many cultures; involves wrapping baby snuggly in cloths or a blanket Outcomes at Birth - Infant mortality: - Death during the first year after birth - In canada, in 2022: 4.7 deaths per 1000 births - Poverty associated with increased infant mortality - Birth weight: - Average newborn: 2500-4500 grams (5.5-9.5 lbs) - Low birth weight (LBW): less than 2500 grams - High level of medical complications; high rates of neurosensory deficits, frequent illnesses, lower IQ scores  - Very low birth weight (VLBW): less than 1500 grams - Premature (preterm) babies: born at or before 37 weeks after conception - Small for gestational age: birth weight is substantially less than normal for gestational age - Causes: teratogens, multiple births Long-term outcomes - Negative effects of birth-weight status gradually diminish for majority of LBW infants - Special services and additional support may be important - Factors like poverty increase risk for preterm birth; through exposure to multiple risk - Preterm infants may experience additional stressors (e.g. from time spent in NICU) - Brain development also at a different stage than babies born at term Intervention factors - Kangaroo care - Breast milk - CCC: cuddled, caressed, and carried - Educational programs Multiple risk models: - Effects of cumulative and multiple risks affect normal functioning in children - Risk range from attachment to language development to well-being Poverty as a developmental hazard - Multiple risks strongly related to lower SES - Structural racism Resilience - When an infant develops successfully even with hazards such as low birth weight, poverty, or teratogens LECTURE 3 Nature and Nurture - Genetic and environmental forces - Genome: complete set of organism’s genes - Findings: - Humans: ~20,000 genes - Shared with most living things - Genotype: inherited genetic material - Phenotype: observed expression of genetic material (genotype) e.g. body characteristics and behaviour - Environment: everything else beyond genes - Development: a combined function of genetic and environmental factors Genetic and Environmental Forces Parents’ genotype → child’s genotype Involves transmission of genetic material from parent to offspring - Chromosomes: molecules of DNA that transmit genetic information - DNA (deoxyribonucleic acid): molecules that carry all the biochemical instructions involved in forming an organism and its functions - Gene: sections of chromosomes that are the basic unit of heredity in all living things Diversity and individuality happen due to several mechanisms - Random assortment of chromosomes in egg and sperm formation - Crossing over: process by which sections of DNA switch from one chromosome to another, promotes variability amongst individuals  - Mutation: a change in a section of DNA - Sex chromosomes (X and Y) that determine an individual’s gender Phenotypes include physical characteristics and behavioural characteristics - Endophenotypes: intermediate phenotypes, including brain and nervous systems, that do not involve overt behaviour; mediate path between genes and behaviour Child’s genotype → child’s phenotype Gene expression: developmental changes - Regulator genes: genes that control activity of other genes; turning off and on Gene expression: dominance patterns - Alleles: - Dominant and recessive alleles - Homozygous and heterzygous - Polygenic inheritance: - Traits are governed by more than one gene - Most relevant type for traits and behaviours of interest to behavioural scientists Child’s environment → child’s phenotype Because of the continuous interaction of genotype and environment, a given genotype may develop differently in different environments - Examples: - Phenylkentonuria (PKU) - Effects of abusive parenting interact with child’s genotype to produce adult outcomes Parental contributions to child’s environemnt - Gene-environment correlations - Parents’ behaviour, preferences, activities are genetically influenced, and these shape the child’s environment - Non-transmitted parental alleles (genetic nurture) Child’s phenotype → child’s environment Children are active creators of their environments - They evoke certain kinds of responses from others - They select surroundings and experiences that match their interests, talents, and personality characteristics Child’s environment → child’s genotype Although the structure of DNA remains “fixed” (mutations aside), certain epigenetic mechanisms can alter functioning of genes - Create stable changes in their expression - Some changes can be passed on to next generation; this altering mediated by the environment Methylation: epigenetic mechanism which silences gene expression most studied in humans - Early life stress, nutrition, toxins and other environmental factors can lead to difference in methylation levels - What is epigenetics? Understanding how our basic biology is influenced by adverse early experiences is relevant for the health and welfare of children Other key points High heritability does not imply immutability: - Experience still plays a role - Interventions are effective Studies of heritability to date have primarily included weird participants: - Lack of diversity in research results in sampling bias  - Goal is to discover genetic and environmental contributions to individual differences in human traits, but with representation in the range of participants included in this research, estimates of heritability could be estimated correctly Environments and complex phenotypes are hard to measure Structures of the Brain Neurons - All neurons have 3 main components: - Cell body: contains basic biological material; keeps neuron functioning - Dendrites: neural fibres that receive input from other cells and conduct it towards cell body as electrical impulses - Axon: neural fibres that conduct electrical signals away from the cell body to connections with other neurons Synapses: microscopic junctions between the axon terminal of one neuron and then dendritic branches or cell body or another neuron(s) Glial cells - Cells in the brain providing critical supportive functions - Form myelin sheath around axons - Myelin sheat: fatty sheath that forms around certain axons in the body; increases spedd and efficiency of neuronal information transmission The cortex - Cerebral cortex constitutes 80% of the human brain - Lobes: major areas of the cortex associated with general categories of behaviour - Occipital lobe: processes visual information - Temporal lobe: associated with memory, emotions, auditory processing - Parietal lobe: spatial processing - Frontal lobe: organizing behaviour, planning ahead - Association areas: lie between major sensory and motor areas, processing and integrating input from there The cortex: cerebral laterialization Cerebral hemispheres: 2 halves of the cortex - For the most part, sensor input from one side of the body goes to the opposite hemisphere of the brain - Corpus callosum: a dense tract of nerve fibers; enables the 2 hemispheres to communicate - Cerebral lateralization: specialization of the brain’s hemispheres for different modes of processing Brain Development Occurs in Stages - Neurogenesis: “baby” neural cells develop inside the neural tube, which eventually becomes the brain and spinal cord - Migration: cells spread out to form all the layers of the brain - Differentiation: once in place turn into mature brain cells (neurons), neurons start to make connections and “talk” to each other Neurogenesis and neuron development - Neurogenesis: - proliferation of neurons through cell division - Begins 42 days after conception - Mostly complete about halfway through gestation  - Then neurons migrate to ultimate destinations Growth, branching and formation of spines: formations on dendrites of neurons that increase capacity of dendrites to form connections with other neurons Myelination: formation of myelin around axons of neurons; speeds and increases information-processing abilities Developmental processes Synpatogenesis: - The process by which neurons form synapses with other neurons - Results in trillions of connections Synapse elimination: - The normal developmental process - Synapses rarely activated get eliminated Overgrowth and Pruning: - Captures experience by fine tuning to what is needed - Can be adaptive (period of opportunity) - But brain is also vulnerable depending on the nature of the experience Individuality is the product of BOTH biological inheritance and personal experiences The importance of Experience Plasticity: capacity of brain to be modeled or changed by experience - Some experiences are “expected” e.g. visual and auditory input; caregiving - Other experience are dependent on the individual e.g. exposure to english or french; sensitive and consistent caregiving Expeected experiences Expected-experience plasticity: describes the role of general human experience in shaping brain development - Heightened vulnerability - Cross-modal reorganization - Sensitive periods Senstive periods: the ability to change the brain decreases over time Experience-dependent plasticity: occurs when neural connections are created and reorganized throughout life as a result of experiences Brain damage and Recovery - Timing is a crucial factor in the ultimate impact of brain damage - Brain can rewire if damaged early in life, when compared with damage later in life; possible because of plasticity, extent of damage also a factor - Worst time to suffer brain damage is very early, during prenatal development; may lead to disorders Point 1: the process of brain development takes a long time Point 2: the child’s brain is not a smaller version of the adult’s brain PRACTICE QUESTIONS: LECTURE 1 Elise is an 11 month old child who has learned that when she points to objects her mother responds with a word. When Elisa is around her mother she points to as many objects as she can see. This is the best illustrates which basic question about child development? A. Nature and nurture B. The active child C. Individual differences D. Research and children’s welfare Answer: B. the active child Short answer quesion: A group of researchers conducted a study to see whether features of children’s temperament were associated with amount of time spent exploring a new piece of playground equipment. They found that children who high on a “shyness” rating spent less time exploring than children who scored lower. The researchers conclude that shyness causes children to be more cautious. Are they justified in their interpretation? why or why not? Answer: Researchers are not justified because their design is correlational. They cannot make a cause-and-effect claim. Short answer question: Provide one example that illustrates how research on child development could be used to develop social policy Answer: Research on childr