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Development Across the Life Span

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Development Across the Life Span

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  1. Development Across the Life Span Chapter 8

  2. Issues in Studying Human Development • Human development – the scientific study of the changes that occur in people as they age from conception until death • Topics include personality, cognition, biological processes, and social interaction in the context of changes that occur as a result of the process of human development

  3. Research Designs • Research in human development is affected by the problem of age • In any experiment, the participants who are exposed to the independent variable (deliberately manipulated) should be randomly assigned to the different experimental conditions • The problem is that in developmental research the age of people in the study should always be an independent variable • But, people can’t be randomly assigned to different age-groups

  4. Research Design • Special designs used in researching age-related changes • Longitudinal design – one group of people is followed and assessed at different times as the group ages • Advantages: see real age-related changes as those changes occur in the same individuals • Disadvantage: lengthy amount of time, money, and effort involved in following participants over the years • Disadvantage: loss of participants when they move away, lose interest, or die • Cross-sectional design – several different age-groups are studied at one particular point in time • Advantage: quick, relatively inexpensive, and easier to accomplish • Disadvantage: doesn’t compare individuals as they age; instead, individuals of different ages are being compared to one another • Cross-sequential design – participants are first studied by means of a cross-sectional design but are also followed and assessed longitudinally

  5. Research Design • Differences between age-groups are often a problem in developmental research • Ex. If comparing the IQ scores of 30 year olds to 80 year olds to see how aging affects intelligence • Questions arise concerning the differing educational experiences and opportunities those 2 age-groups have had that might affect IQ scores, in addition to any effects of aging

  6. Nature versus Nurture • Nature – refers to heredity, the influence of our inherited characteristics on our personality, physical growth, intellectual growth, and social interactions • Nurture – the influence of the environment on personality, physical growth, intellectual growth, and social interactions • Anything that can influence development that does not come from within the person • Most developmental psychologists now agree that who people are and what they become is the product of an interaction between nature and nurture • But, this doesn’t mean that the nature vs. nurture controversy is over • Ex. Intelligence is still a “hot topic” with regard to how much is inherited and how much is learned • Researchers and theorists assume a large genetic influence • Whereas many believe that culture, economics, nutrition in early childhood, and educational opportunities have a greater impact • FYI: research on identical twins suggests that genetics are responsible for about 50% of intelligence

  7. The Basic Building Blocks of Development: Chromosomes, Genes, and DNA • Genetics – the science of heredity and inherited traits • DNA (deoxyribonucleic acid) – special molecule that contains the genetic material of an organism • Gene – section of DNA having the same arrangement of chemical elements • Genes are located on chromosomes • Chromosome – tightly wound strand of genetic material or DNA • Rod-like structures found in the nucleus of each cell in an organism

  8. Chromosomes, Genes, and DNA • Humans have 46 chromosomes in each cell of the body • 23 come from the mother’s egg • 23 come from the father’s sperm • Most characteristics are determined by the first 22 pairs, called autosomes • The 23rd pair determine the person’s sex, and are called sex chromosomes • XX = female • XY = male

  9. Dominant and Recessive Genes • The 46 chromosomes can be arranged in pairs (one member of each pair comes from the mother and the other comes from the father) • Dominant – a gene that actively controls the expression of a trait • Recessive – a gene that only influences the expression of a trait when paired with an identical recessive gene • Ex. Hair color • brown is the most dominant hair color gene (B) • Blond is the most recessive hair color gene (b) • BB = brown hair • Bb = brown hair • bB = Brown hair • bb = blonde hair

  10. Dominant and Recessive Genes • In reality, the patterns of genetic transmission of traits are usually more complicated that just dominant and recessive • Almost all traits are controlled by more than one pair of genes in a process called polygenic inheritance • Sometimes certain kinds of genes tend to group themselves with certain other genes • Ex. genes for blond hair and blue eyes • Other genes are so equally dominant or recessive that they combine their traits • Ex. Gene for blond hair and gene for red hair • If a child gets both a blond and a red gene, instead of one or the other controlling the child’s hair color, they may blend together to form strawberry-blond

  11. Genetic and Chromosome Problems • Several genetic disorders are carried by recessive genes • these diseases are inherited when a child gets 2 recessive genes, one from each parent • Examples: • Cystic fibrosis: disease of the respiratory and digestive tracts • Sickle-cell anemia: blood disorder • Tay-sachs disorder: fatal neurological disorder • Phenylketonuria (PKU): inability to break down phenylalanine, an amino acid controlling coloring of the skin and hair • If levels of phenylalanine build up, brain damage can occur, and if untreated, results in severe intellectual disabilities

  12. Genetic and Chromosome Problems • Sometimes the chromosomes itself is the problem • Each egg and sperm are only supposed to have 23 chromosomes • But, sometimes when these cells are created a chromosome can end up in the wrong cell, leaving one cell with only 22 and the other with 24 • If either of these cells survives to “mate” the missing or extra chromosome can cause mild to severe problems in development • Examples • Down syndrome: there is an extra chromosome in what would normally be the 21st pair • Symptoms include physical characteristics of almond-shaped, wide-set eyes, and intellectual disability

  13. Genetic and Chromosome Problems • Other chromosome disorders occur when there is a problem with the sex chromosomes (the 23rd pair) • Examples • Klinefelter’s syndrome: the 23rd set of chromosomes is XXY • The extra X produces a male with reduced masculine characteristics, enlarged breasts, obesity, and excessive height • Turner’s syndrome: the 23rd pair is missing an X • Females with a single X chromosome tend to be very short, infertile, and sexually underdeveloped

  14. Prenatal Development • From conception to the actual birth of the baby is a period of approx. 9 months • During which a single cell becomes a complete infant • Also, during this time, many things can have a positive or negative influence on the developing infant

  15. Fertilization, The Zygote, and Twinning • Ovum – the female sex cell, or egg • Fertilization – the union of the ovum and sperm • Zygote – cell resulting from the uniting of the ovum and sperm • When an ovum and a sperm unite in the process of fertilization, the resulting single cell will have a total of 46 chromosomes and is called a zygote • Normally, the zygote will begin to divide • First into two cells, then four, then eight, and so on, with each new cell also having 46 chromosomes • Because the DNA molecules produce duplicates, or copies, of themselves before each division • Eventually, the mass of cells becomes a baby • Sometimes this division process doesn’t work exactly this way, and twins or multiples are the result

  16. Fertilization, The Zygote, and Twinning • 2 kinds of twins • Monozygotic twins – identical twins formed with one zygote splits into two separate masses of cells, each of which develops into a separate embryo • The infants will be the same sex and have identical features because they posses the same set of 46 chromosomes • Dizygotic twins – often called fraternal twins, occurring when two individual eggs get fertilized by separate sperm, resulting in two zygotes in the uterus at the same time • The woman’s body either releases 2 eggs at one time or releases another egg in a later ovulation period after the first conception • This is more likely to happen to women who are taking fertility drugs to help them get pregnant

  17. Fertilization, The Zygote, and Twinning • For developmental psychologists, twins provide an important way to look at the contribution of nature and nurture to human development • Researchers may seek out identical twins who have been separated at birth • Looking at all the ways those twins are alike in spite of being raised in different environments • Sometimes in the twinning process, the mass of cells does not completely split apart • When this occurs, conjoined twins are the result, and they will be joined a the point where the two cell masses remained “stuck” • This joining may involve only soft tissues or may involve the sharing of certain body parts • Text page 304-305

  18. The Germinal Period • Germinal period – first 2 weeks after fertilization, during which the zygote moves down to the uterus and begins to implant in the lining • Once fertilization has taken place, the zygote begins dividing and moving down to the uterus, the muscular organ that will contain and protect the developing infant • Takes about 2 weeks • Followed by about a week during which the mass of cells, now forming a hollow ball, firmly attaches itself to the wall of the uterus • The placenta also begins to form during this period • Placenta is a specialized organ that provides nourishment and filters away the developing baby’s waste products • The umbilical cord also begins to develop at this time, connecting the organism to the placenta

  19. The Germinal Period • Cells also begin to differentiate, or develop into specialized cells • In preparation for becoming all the various kinds of cells that make up the human body • Ex. Skin cells, heart cells, etc • Perhaps the most important of these cells are the stem cells, which stay in a somewhat immature state until needed to produce more cells • Researchers are looking into ways to use stem cells found in the umbilical cord to grow new organs and tissues for transplant or to repair neurological damage

  20. The Embryonic Period • Embryo – name for the developing organism from 2 weeks to 8 weeks after fertilization • Organism is called an embryo after it is firmly attached to the lining of the uterus • Embryonic period – the period from 2-8 weeks after fertilization, during which the major organs and structures of he organism develop • By the end of the 8 weeks, the embryo is about 1 inch long and has primitive eyes, nose, lips, teeth, and little arms and legs, as well as a beating heart • Although no organ is fully developed or completely functional, nearly all are “there”

  21. Critical Periods • As soon as the embryo begins to receive nourishment from the mother through the placenta, it becomes vulnerable to hazards • Such as diseases of the mother, drugs, and other toxins that can pass from the mother through the placenta to the developing infant • It is during the embryonic period that we most clearly see critical periods – times during which certain environmental influences can have an impact on the development of the infant • Structural development of the arms and legs is only affected during the time these limbs are developing: 3 ½ - 8 weeks • The heart’s structure is most affected very early: 2 ½ - 6 ½ weeks • Physical and structural problems with the central nervous system: 2 – 5 weeks • Eyes: 3 ½ - 8 ½ weeks • Teeth and roof of the mouth: 7 – 12 weeks

  22. Prenatal Hazards: Teratogens • Teratogen – any factor that can cause a birth defect, such as a drug, chemical, or virus

  23. The Fetal Period • Fetal period – the time from about 8 weeks after conception until the birth of the baby • Fetus – name for the developing organism from 8 weeks after fertilization to the birth of the baby • Fetal period is a time of tremendous growth • The fetus’s length increases by about 20 times and its weight increases from about 1 ounce at 2 months to an average of a little over 7 lbs at birth • The organs continue to develop and become functional • At this time, teratogens will more likely affect the physical functioning of the organs rather than their structure • Ex. The functioning of the central nervous system, eyes, and external sex organs are vulnerable throughout the fetal period

  24. The Fetal Period • 3rd month: muscles begin to contract • 4th month: the mother will begin to feel this movement as a tiny “flutter” or “quickening” at first • 5th month: the flutter will become a “kick” • The last few months: continue the development of fat and the growth of the body • 38th week: the fetus is pushed out of the mother’s body in the process of labor and childbirth and becomes a baby • Babies born before 38 weeks are called preterm and may need life support to survive • This is especially true if the baby weighs less than 5 ½ lbs at birth 3 months 4 months 5 months 38 weeks

  25. The Fetal Period • The most likely time for a miscarriage, or spontaneous abortion, is in the first 3 months, as the organs are forming and first becoming functional • 15-20% of all pregnancies end in miscarriage, many so early that the mother may not have even known she was pregnant • Miscarriages are most likely caused by a genetic defect in the way the embryo or fetus is developing that will not allow the infant to survive • In other words, there isn’t anything that the mother did wrong or that could have been done to prevent the miscarriage

  26. Infancy and Childhood Development • Surprisingly, babies can do a lot more than researchers used to believe they could • A lot of early research on infants just after birth was conducted while babies were still very drowsy from the general anesthesia administered to their mothers during the labor process • Drowsy babies don’t tend to respond well • However, it is now obvious that infants accomplish a great deal throughout infancy • Even in the first few days of life outside the womb

  27. Physical Development • Immediately after birth several things start to happen • The respiratory system begins to function, filling the lungs with air and putting oxygen into the blood • The blood now circulates only within the infant’s system because the umbilical cord has been cut • Body temperature is now regulated by the infant’s own activity and body fat (which acts as insulation) rather than by the amniotic fluid • The digestive system takes the longest to adjust to life outside the womb • This is another reason for the baby’s excess body fat, it provides fuel until the infant is able to take in enough nourishment on its own • That’s why most babies lose a little weight in the first week after birth

  28. Reflexes • Infants have a set of innate involuntary behavior patterns called reflexes • Until a baby is capable of learning more complex means of interaction, reflexes help it to survive • 5 infant reflexes, used to determine whether or not a newborn’s nervous system is working • If a reflex is absent or abnormal, it may indicate brain damage or some other neurological problem

  29. 5 Infant Reflexes • Grasping reflex • Startle reflex • Rooting reflex (when you touch its cheek it will turn toward your hand, open its mouth, and search for a nipple) • Stepping reflex • Sucking reflex

  30. Sensory Development • Most of the sensory systems are fairly well developed at birth, but some require more time to fully develop • Sense of touch is the most well developed at birth • Which makes sense given the amount of amount of skin to womb contact the baby had in the last months of pregnancy • Sense of smell is also highly developed • Breast fed babies can tell the difference between their own mother’s milk scent and another woman’s milk scent within a few days after birth • Sense of taste is nearly fully developed • At birth, infants show a preference for sweets (human breast milk is very sweet) • By 4 months babies develop a preference for salty tastes (possibly due to exposure to the salty taste of their mother’s skin) • Sour and bitter tastes produce spitting up and the making of horrible faces

  31. Sensory Development • Hearing is functional before birth but may take a little while to reach full potential • The fluids of the womb first must clear out of the auditory canals completely • From birth, newborns seem most responsive to high pitches, like a woman’s voice, and low pitches, like a man’s voice • Vision is the least functional sense at birth • The eye is a very complex organ and takes a while to fully develop • The rods, which see in black and white and have little visual acuity, are fairly well developed at birth • But the cones, which see color and provide sharpness of vision take about 6 months to fully develop • So, the newborn has relatively poor color perception until about 2 months of age and has fairly “fuzzy” vision, like that of a nearsighted person • The lens of the newborn stays fixed until the muscles that hold it in place mature • Until then, the newborn is unable to shift what little focus it has from close to far • Thus, newborns have a fixed distance for clear vision, about 7-10 inches, which is the distance from the baby’s face to the mother’s face while nursing

  32. Sensory Development • Newborns also have visual preferences at birth, as discovered by measuring the amount of time infants spend looking at different things • Prefer complex patterns over simple ones • Prefer 3 dimensions over 2 • Suggests that they possess depth perception • Prefer human faces and human voices • Which makes it easier for them to form relationships with their caregivers and to develop language later on

  33. Classic Study: The Visual Cliff • Gibson & Walk: tested babies for depth perception on the visual cliff • Visual cliff is a table that has an apparent drop-off on one side • The surface of the table on both the deep and shallow side is covered in a patterned table cloth, so that the different size of the patterns is a cue for depth • Remember size constancy, if something looks smaller, people assume it is farther away • The whole table is covered by a clear-glass top, so that a baby can safely be placed on or crawl across the deep side

  34. Classic Study: The Visual Cliff • Infants tested on the visual cliff ranged from 6-14 months in age • The were placed on the middle of the table and then encouraged (usually by their mothers) to crawl over either the shallow or the deep side • Most babies, 81%, refused to crawl over the deep side, even though they could touch it with their hands and feel that is was solid • They were upset and seemed fearful when encouraged to crawl across • This was interpreted as a very early sign of the concept of depth perception

  35. Motor Development • There is a tremendous development of motor skills from birth to about 2 years of age • Remember, theses ranges are averages and an infant may reach these milestones earlier or later than the averages and still be considered to be developing normally

  36. 6 Motor Milestones • Raising head and chest: 2-4 months • Rolling over: 2-5 months • Sitting up with support: 4-6 months • Sitting up without support: 6-7 months • Crawling: 7-8 months • Walking: 8-18 months This pattern is seen in early control of the neck muscles and the much later development of the control of the legs and feet

  37. Cognitive Development • By the time the average infant has reached the age of 1 year, it has tripled its birth weight and added about a foot to its height • The brain triples its weight in the first 2 years, reaching about 75% of this adult weight • By age 5, the brain is at 90% of its adult weight • This increase makes a tremendous amount of major advances in cognitive development possible • Cognitive development – the development of thinking, problem solving, and memory

  38. Piaget’s Theory: Four Stages of Cognitive Development • One of the 3 ways of examining the development of cognition is the work of Jean Piaget • Piaget developed his theory from detailed observations of infants and children, especially his own 3 children • He made significant contributions to the understanding of how children think about the world • His theory shifted the commonly held view at the time that children’s thinking was that of “little adults” toward recognition that it was actually quite different from adult thinking

  39. Piaget’s Theory: Four Stages of Cognitive Development • Piaget believed that children form mental concepts or schemes as they experience new situations and events • Scheme – a mental concept formed through experiences with objects and events • Ex. Is Sandy points to a picture of an apple and tells her child “that’s an apple,” the child forms a scheme for “apple” that looks something like the picture • Piaget also believed that children first try to understand new things in terms of schemes they already possess, a process called assimilation • Ex. The child might see an orange and say “apple” because both objects are round • When corrected, the child might alter the scheme for apple to include “round” and “red” • The process of altering or adjusting old schemes to fit new information and experiences is called accommodation • Piaget also proposed 4 distinct stages of cognitive development that occur from infancy to adolescence

  40. Piaget’s Theory: Sensorimotor Stage 1 • Sensorimotor stage – first stage of cognitive development in which the infant uses its senses and motor abilities to interact with objects in the environment • Birth-2 years • At first, infants only have the involuntary reflexes present at birth to interact with objects and people • As their sensory and motor development progresses, they begin to interact deliberately with objects by grasping, pushing, tasting, etc. • Infants move from simple repetitive actions (ex. Grabbing their toes) to complex patterns (ex. Trying to put a shape into a sorting box)

  41. Piaget’s Theory: Sensorimotor Stage 1 • By the end of the sensorimotor stage, infants have fully developed a sense of object permanence • Object permanence – the knowledge that an object exists even when it is not in sight • Ex. The game of “peek-a-boo” is important in teaching infants that their mother’s smiling face is always going to be behind her hands • Object permanence is a critical step in developing language (and eventually abstract thought) • Because words themselves are symbols of things that may not be present • Symbolic thought – the ability to represent objects in one’s thoughts with symbols such as words • Becomes possible by the end of the sensorimotor stage • Children at age 2 are capable of thinking in simple symbols and planning out actions

  42. Piaget’s Theory: Preoperational Stage 2 • Preoperational stage – second stage of cognitive development in which the preschool child learns to use language as a means of exploring the world • Ages 2-7 • Children can now move freely in their world and no longer have to rely only on senses and motor skills • They can now ask questions and explore their surroundings more fully • Pretending and make-believe play become possible because children at this stage can understand, through symbolic though, that something can “stand” for something else • Ex. A line of wooden blocks can “stand in” for a train

  43. Piaget’s Theory: Preoperational Stage 2 • Children in this stage are limited in several ways • They are not yet capable of logical thought • They can use simple mental concepts but are not able to use those concepts in a more rational, logical sense • They believe that anything that moves is alive (called animism) • They tend to believe that what they see is literally true • Ex. When children see Santa Claus in a book, on TV, or at the mall, Santa becomes real to them • They don’t think about how Santa might get to every child’s house in one night or why those toys he delivers are the same ones they saw in the store last week • They may be able to count up to 10 or 20, but they won’t realize that two rows of the same number of items are the same, if one row is spaced farther apart and looks longer • They focus on the appearance of the 2 rows • This is called conservation

  44. Piaget’s Theory: Preoperational Stage 2 • Conservation – the ability to understand that simply changing the appearance of an object does not change the object’s nature • Conservation of number • Conservation of liquid

  45. Piaget’s Theory: Preoperational Stage 2 • Another limitation of this stage is egocentrism – the inability to see the world through anyone else’s eyes but one’s own • The child thinks that everyone else must see that they see and think that what is important to them must be important to everyone else • Ex. A 2 year old who has crawled out of her crib is told by her mother “I don’t want to see you in that living room again tonight!” so the next time she comes into the room she puts her hands over her eyes, thinking that if she can’t see her mother, her mother can’t see her • Egocentrism is not the same thing as being egotistical or selfish • Ex. A 4 year old boy may want to buy his grandmother an action figure for her birthday because that’s what he would want, and therefore, what she must want as well

  46. Piaget’s Theory: Preoperational Stage 2 • Centration – the tendency of young children to focus only on one feature of an object while ignoring other relevant features • Remember that children in this stage are overwhelmed by appearance (like in the conservation tasks) • Children will focus, or center, on the length of the row of items and ignore the number of items • Centration is one of the reasons children in this stage often fail to understand that changing the way something looks doesn’t change its substance (like in the conservation tasks) • Another reason children fail conservation tasks is because of irreversibility – the inability of the young child to mentally reverse an action • Ex. In the conservation of liquid task, the child fails to conserve the volume of liquid as it takes on a different shape in the taller glass • Not only because the child centers on the height of the liquid but also because the child cannot imagine pouring the liquid back into the first glass and having it be the same amount again

  47. Piaget’s Theory: Concrete Operations Stage 3 • Concrete operations stage – third stage of cognitive development in which the school-age child becomes capable of logical thought processes but is not yet capable of abstract thinking • Ages 7-12 • Children are now capable of conservation and reversible thinking • Centration no longer occurs as children become capable of considering all the relevant features of any given object • They begin to think more logically about beliefs such as Santa Clause and ask questions, eventually coming to their own more rational conclusions • They are in school, learning all sorts of science and math and are convinced that they know more than their parents at this point