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Chapter 12

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Psychology 1000

CHAPTER 12 Sunday, February 2, 2014 11:51 AM DEVELOPMENTAL PSYCHOLOGY: ISSUES AND METHODS • Four broad issues guide developmental research: o Nature and Nurture o Critical and sensitive periods: A critical period is an age range in which certain experiences must occur for development to proceed normally or along a certain path • A sensitive period is an optimal age range for certain experiences, but if those experiences occur at another time, normal development will still be possible o Continuity versus discontinuity - is development continuous and gradual or discontinuous o Stability versus change • Developmental psychologists address these issues by plotting (describing) developmental functions that portray how different processes change with age. The following five developmental functions are shown with different shapes: o No change- an ability present at or before birth that remains relatively constant across the lifespan o Continuous change (continuity) - an ability not present, or very immature, at birth that develops gradually over months or years and then remains constant over age o Stages (discontinuity) - an ability that progresses in stages, with relatively rapid shifts from a lower level of performance to a higher level o Inverted U-shaped function - an ability that emerges after birth, peaks and disappears with age o U-shaped function- an ability that is present early in life, disappears temporarily, and emerges later • Using a cross-sectional design, we would compare people of different ages at the same point in time → it is widely used because data from many age groups can be collected relatively quickly, but a key drawback is that the different age gorups, called cohorts, grew up in different historical perids • To avoid this problem, a longitudinal design repeatedly tests the same cohort as it grows older → unfortunately, it is time consuming and, as years pass, our sample may shrink substantially as people move, drop out of the study, or die • Sequential design combines the cross-sectional and longitudinal approaches → we can repeatedly test several age cohorts as they grow older and determine whether they follow a similar developmental pattern (most comprehensive but also the most time-consuming and costly) PRENATAL DEVELOPMENT • Consists of three stages of physical growth: o The germinal stage constitutes approximately the first two weeks of development, beginning when one sperm fertilizes a female egg (ovum) → this female egg is called a zygote (through repeated cell division the zygote becomes a mass of cells that attaches to the mother's uterus about 10 to 14 days after conception o The embryonic stage extends from the end of the second week through the eighth week after conception, and the cell mass now is called an embryo • Two life-support structures, the placenta and umbilical cord, develop at the start of this stage • Located on the uterine wall, the placenta contains membranes that allow nutrients to pass form the mother's blood to the umbilical cord • In turn, the umbilical cord contains blood vessels that carry these nutrients and oxygen to the embryo, and waste products back from the embryo to the mother • Supplied with nutrients, embryonic cells divide rapidly and become specialized • Bodily organs begin to form, and by week eight the heart of the 2-cm-long embryo is beating, the brain is forming, and facial features, such as eyes, can be recognized • At the ninth week after conception the embryo is called a fetus - during this fetal stage, which lasts until birth, muscles become stronger and other bodily systems continue to develop → at about 24 weeks the eyes open, and by 28 weeks the fetus attains the age of viability, meaning that it is likely to survive outside the womb in case of premature birth Genetics and Sex Determination • At conception, an egg and sperm unite to form the zygote, which now contains the full set of 23 pairs found in other human cells • The 23rd pair determines the baby's sex (XX- female, XY-male) • The Y chromosome contains a specific gene, known as the TDF (testis determining factor) gene, that triggers male sexual development • At roughly 6-8 weeks after conception the TDF gene initiates the development of testes - once formed, the testes secrete sex hormones called androgens that continue to direct a male pattern of organ development Environmental Influences • Teratogens are environmental agents that cause abnormal prenatal development. The placenta prevents many dangerous substances from reaching the embryo and fetus, but some harmful chemical molecules and diseases can pass through • Sexually transmitted diseases can pass from mother to fetus and produce brain damage, blindness and deafness, depending on the disease • Mercury, lead, radiation, and many other environmental toxins also produce birth defects, as can many drugs. Fetal alcohol syndrome (FAS) is a group of severe abnormalities that results from prenatal exposure to alcohol o FAS children have facial abnormalities that results from prenatal exposure to alcohol o Psychological symptoms of FAS may include intellectual (IQ) and fine-and gross- motor impairments and poor adaptive functioning o The threshold level of alcohol exposure needed to produce FAS is not known • Maternal smoking increases the risk of miscarriage, premature birth, and low birth weight o Because of second-hand smoke, regular tobacco use by fathers also has been linked to low infant birth weight and increased risk of respiratory infections o Babies of pregnant mothers who regularly use heroin or cocaine are often born addicted and experience withdrawal symptoms after birth • Kisilevsky and Muir (1991) found that relatively loud sounds elicited reliable increases in fetal heart rate and body movements during the 3rd trimester of pregnancy • Fetuses also learn - they stop responding to repeated presentations of vibroacoustic and auditory stimuli, reflecting short-term memory • They also have long-term memory for sounds they hear repeatedly during fetal development •Fetuses also learn about odours from their pregnant mother's diet. The newborns of mothers who habitually consume anise-flavoured foods and drinks also preferred anise odours, while those of non-anise consuming mothers responded either neutrally or showed aversion to anise odours INFANCY AND CHILDHOOD The Amazing Newborn •William James suggested that the newborn's world is a "buzzing, blooming confusion" - that is, that they are passive, disorganized, and have an empty mind Newborn Sensation and Perception •Robert Fantz (1961) used the preferential looking procedure to study infants' visual preferences o Placed infants on their backs, showed them two or more stimuli at the same time, and filmed their eyes to record how long they looked at each stimulus o Infants preferred complex patterns, such as realistic or scrambled drawings of a human face, to simple patters and solid colours •Infants do not have poor visual acuity - when gratings (black and white vertical stripes) are paired with an equally bright grey field, and the side of the grating and size of the stripes are varied across trials, infants look longer at the grating when the stripes are wide. As the width is reduced, at some point their preference disappears, defining newborn's resolution threshold at about 20/800, or 40 times worse than normal adult acuity of 20/20 •Newborns readily turn toward off-centred auditory and tactile targets→ thus newborns orient to significant stimuli in their environment, the most important being their mother's face, voice and smell, optimizing their access to food, warmth and social stimulation Newborn Learning •Within hours after birth, they distinguish the familiar face of their mother from that of a female stranger-they look longer at the mother's face •A new visual preference can be established in newborns by using the visual habituation procedure - the same stimulus is presented repeatedly until infant looking time declines (usually by 50%) •Philip Zelazo used an auditory habituation procedure to study infant memory o Recorded 2-day-old's head-turning toward an off-centred, recorded speech sound o After about 16 presentations, infants stopped turning to face the now familiar sound - they were not simply fatigued because • By the end of habituation, many infants were turning away from the sound, perhaps trying to avoid it; • They readily turned toward a novel sound (Beagle), indicating that they could discriminate between some adult speech sounds; • Partial habituation to the osund lasted for at least 24 hours, reflecting the operation of long-term memory •Newborns can learn through classical and operational conditioning and imitation •Meltzoff and Moore reported that newborns will imitate some adult facial expressions → they suggest that this innate ability helps infants recognize people and engage them in social exchange Sensory-Perceptual Development •Newborns' visual field in each eye expands to almost adult size by 6 months of age, while grating acuity improves in a continuous developmental function from 20/800 at birth to 20/100 by 6 months of age, and then progresses more slowly until it reaches adult levels by about 4 years of age • Researcher, using visual habituation and preference procedures, have shown that around 3-4 months of age, infant pattern perception is organized according to certain Gestalt principles • Auditory pattern perception is also relatively advanced in young infants, who can detect tiny changes in adult speech sounds that differentiate ne work from another (called phonemes) by 1 to 2 months of age • As early as 2 months of age, infants remember a short melody after listening to it repeated 15 times; and, they discriminate if from a novel melody • Masataka hypothesized that his primitive early musical appreciation reflects an early stage in the musical appreciation reflects an early stage in the evolution of our communication system composed of melodies rather than words Physical, Brain, and Motor Development • Thanks to maturation , the genetically programmed biological process that governs our growth, our bodies and movement (motor) skill
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