Chapter 5 Perceptual Physical Motor Development in Infancy Physical Growth First Two Years Changes in Height and Weight o Birth weight typically doubles by 5 months 15lbs and triples by the first birthday 22lbs Height increases by about half in the first year to 30 inches o It has been shown that a babies tend to grow in spurts rather than in an even progression o Parents must gain in muscle strength with the increasing weight of the baby and some suffer from the physical strain Changes in Body Proportions o Cephalocaudal principle head to tail growth of the head and upper body precede growth in the lower body Eight weeks after conception the head is half the fetus s length at birth it is 25 of the body length whereas by adulthood the head accounts for 12 of body length and the legs account for about 50 o Proximal principle near to far the body grows from the center outward This principle reverses just before puberty Childproofing the Environment crawl walk or run Nutrition in Infancy o Collective sets of precautions should be taken to ensure the safety of babies who begin to o Formulas made for mothers who choose not to breast feed are nutritionally acceptable and meet the needs fro fats protein carbs minerals and vitamins However there is research that shows several health advantages for breast milk over formula Breast feeding promotes the early development of the infant s brain and has positive effects on long term cognitive intellectual development Breast milk offers the baby a distinct immunological benefit that cannot be duplicated in formula Immunological protection can be transmitted to the infants in the colostrum a thin yellowish fluid secreted by the breast for several days before milk is produced The colostrum contains antibodies that cannot be replicated in formula Infants who are breast fed are less likely to become obese in childhood Mother s who breast feed return more quickly to their pre pregnancy weight There is also evidence of a lower rate of breast cancer and ovarian cancer in mothers who breast feed AAP recommends that mothers breast feed their infants exclusively for the first six months of life and six months after including solid food o Less than 50 of women make an attempt to breast feed o Baby s nutrition is NOT the same as adults Development of the Brain Structure of the Brain o Proliferation of nerve cells is extremely rapid during the early prenatal stage resulting in approximately 100 billion nerve cells in a newborn The neuron transmits impulses from the dendrites to the cell body and from the cell body to the axon o Synapse a microscopic gap where the axon of one cell butts up against the dendrite of another cell o Neurotransmitters chemicals that transmit impulses across the synapse o At approximately 28 weeks of gestation a process known as myelination occurs where axons develop an insulating fatty coating that improves the efficiency of nerve impulse transmission It continues through childhood and to some extent into adulthood Methods of Study for Perceptual Development o Synapses begin to develop in very large numbers prenatally and continue to increase in extraordinary large numbers throughout he first 3 years of life in a process called synaptogenesis Plasticity of the Brain o Plasticity if one part of the nervous system becomes damaged or unable to function other parts of the system will be able to take over A dramatic demonstration of plasticity is shown in surgical hemispherectomy the radical removal of half of a child s brain in the treatment of extreme cases of brain seizures After surgery the child s brain begins to reprogram itself along with persistent therapy o After the end of the second year the rate of production of new synapses disappears The elimination process is based on a simple principle pathways that get used repeatedly survive those that go unused disappear This use it or lose it principle results in a leveling of the number of synapses from the end of the second year through approximately the tenth year The repetitions of certain pathways ensure the survival of the neurons and the synapses that make up the path Pruning a massive and destructive process in which synapses and cells that are not stimulated are eliminated This process results in about 50 of the synapses in an adult brain that were in a 3 year old o Thus children who experience more varied more patterned more organized more repetitious and more consistently challenging interaction with their environment will have better developed brains than children who have these experiences to a lesser degree Sensation refers to the ability to passively receive and register information concerning internal and external events and to transmit the information to the central nervous system Perception refers to the infants active searching for information and the processing of that sensory information by the brain There are challenges to researching sensation and perception in infants 1 infants are much more vulnerable to injury than older age children 2 Infants are incapable of expressing their willingness to participate in a research study 3 Infants are incapable of providing verbal response to questions or probes o Researchers must design safe methods of study for infants Also they must inform parents and have them sign a consent form to participate in the research activity Visual preference method the researcher presents pairs of stimuli to the baby The researcher determines which stimulus the infant s looking at by the refection of the fixated stimulus on the pupil of the infant s eye Electroencephalography the measurement and interpretation of electrical activity in the brain Variations in the brain wave patterns to different stimuli are interpreted as indications that the infant has perceived the stimuli as different Habituation dishabituation researchers take advantage of the fact that like adults infants react to changes in sound smell taste or visual display by staring blinking ducking reaching or blushing and or by changes in heart rate and respiration o As a particular stimulus is repeated over and over at the same intensity infants habituate to the stimulus the intensity of their responses steadily decrease o The researchers look for changes in habituation when a new stimulus is received High amplitude sucking researchers use of a special pacifier with an internal sensing device that indicates when the infant s rate or intensity of sucking increases If an infant
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