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  1. 1. PSYC 50 Developmental Psychology SECTION 3: INFANCY Chapter 5: Physical Development in Infancy PHYSICAL GROWTH AND DEVELOPMENT IN INFANCY  Cephalocaudal and Proximodistal Patterns o Cephalocaudal pattern: the sequence in which the earliest growth always occurs at the top—the head— with physical growth in size, weight, and feature differentiation gradually working from top to bottom. o Proximodistal pattern: the sequence in which growth starts at the center of the body and moves toward the extremities.  Height and Weight o The average North American newborn is 20 inches long and weighs 7 ½ pounds. o 95% of full term newborns are 18-22 inches long and weigh between 5 ½ and 10 pounds. o In the first several days of life, most newborns lose 5- 7% of their body weight. Once they adjust to sucking, swallowing, and digesting, they grow rapidly, gaining an average of 5-6 ounces per week during the 1st month. o Doubled their birth weight by the age of 4 months and have nearly tripled it by 1st birthday. o Grow 1 inch per month during 1st year. o Rate of growth is slower in the 2nd year. o 2 years – 26 to 32 pounds, reached 1/5 of adult weight. o 2 years – 32 to 35 inches in height, nearly half of adult height.  The Brain o Neuron: nerve cell that handles information processing at the cellular level. o The Brain’s Development Because the brain is still developing so rapidly in infancy, the infant’s head should never be shaken.  Shaken baby syndrome – includes brain swelling and hemorrhaging.  At birth, brain is about 25% of its adult weight.  2nd birthday, 75% of adult weight  Myelin sheath – insulates nerve cells and also helps nerve impulses travel faster.  Myelination –the process of encasing axons with fat cells, begins prenatally and continues after birth.  Myelination for visual pathways, completed in 1st 6 months. Auditory myelination, until 4 or 5 years of age. Some continue even into adolescence.  One of the most dramatic changes in the 1st 2 years of life is the spreading connections of dendrites to each other.  Another important aspect at the cellular level is the dramatic increase in connections between neurons.  Synapses – tiny gaps between neurons where chemical interactions connect axons and dendrites, allowing information to pass from neuron to neuron.  Using the electroencephalogram (EEG), which measures the brain’s electrical activity, researchers have found that a spurt in EEG activity occurs at about 1 ½ to 2 years of age. Other spurts seem to take place at about 9, 12, 15, and 18 to 20 years.  Spurts of brain activity may coincide with important changes in cognitive development.  Charles Nelson (1999, 2003), by attaching up 128 electrodes to a baby’s scalp, he has found that even newborns produce distinctive brain waves that reveal they can distinguish their mother’s voices from another woman’s even while they are asleep. o Brain’s Lobes and Hemispheres  Forebrain, the highest level of the brain. Consists of a number of structures, including the cerebral cortex-80% of the brain’s volume and covers the lower portions of the brain.  Cerebral cortex – perception, language, and thinking  The cerebral cortex is divided into 2 halves, or hemispheres. Each hemisphere is divided into 4 main areas called lobes: Frontal – voluntary movement and thinking Occipital – vision Temporal – hearing Parietal – processing information about body
  2. 2. sensations.  Lateralization – specialization of function in one hemisphere of the cerebral cortex or the other. o Early Experience and the Brain  Neural connections are formed early in life. The infant’s brain literally is waiting for experiences to determine how connections are made. Before birth, it appears that genes mainly direct how the brain establishes basic wiring patterns.  Neurons grow and travel to distant places awaiting further instructions.  After birth, environmental experiences guide the brain’s development.  Michael Rehbein  Sleep Newborns sleep 16-17 hours a day, although some sleep more and others less. The range is from about 10 hours to about 21 hours, and the longest period of sleep is not always between 11PM and 7AM. o REM Sleep  Half of an infant’s sleep is REM sleep, and infants often begin their sleep cycle with REM sleep rather than non-REM sleep.  3 months-time spent in REM sleep falls to 40%, and REM sleep no longer begins their sleep cycle.  REM sleep might promote the brain’s development in infancy.  Infants sleep far more than children and adults, and a much greater amount of time is taken up by REM sleep in infancy that at any other point in the life span. o Shared Sleeping  Sharing a bed with a mother is a common practice in many cultures, whereas in others, newborns sleep in a crib, either in the same room as the parents, or in a separate room.  Some child experts believe that shared sleeping is beneficial, promoting breast feeding, responding more quickly to the baby’s cries, and detecting potentially dangerous breathing pauses in the baby.  American Academy of Pediatrics Task Force on Infant Positioning and SIDS (AAPTFIPS) (2002) discourages shared sleeping.  Sudden Infant Death Syndrome – a condition that occurs when an infant stops breathing, usually during the night, and suddenly dies without an apparent cause.  It is recommended that the infant’s bedding provide firm support and cribs should have side rails. o SIDS  Highest cause of infant death in the US with nearly 3,000 infant deaths annually attributed to SIDS.  Risk is highest at 4-6 weeks of age.  Since 1992, the AAP has recommended that infants be placed to sleep on their backs to reduce the risk of SIDS. In addition to sleeping in a prone position, researchers have found that the following are risk factors for SIDS:  Low birth weight infants are 5 to 10 times more likely to die of SIDS.  Infants whose siblings have died of SIDS are 2-4 times as likely to die of it.  6% of infants with sleep apnea, a temporary cessation of breathing in which the airway is completely blocked, usually 10 seconds or longer, die of SIDS.  More common in lower socioeconomic status.  More common in infants who are passively exposed to cigarette smoke.  More common if infants sleep in soft bedding.  Nutrition o Nutritional Needs and Eating Behavior  From birth to 1 year, human infants nearly triple their weight and increase their length by 50%.  Nutritionists recommend that infants consume approximately 50 calories/day for each pound they weigh.  Scheduled feeding versus demand feeding  Does the same type of nutrition that makes us healthy adults also make young infants healthy?  For growing infants, high-calorie, high- energy foods are part of a balanced diet.  French fries were the most common vegetables the babies ate. o Breast versus Bottle Feeding  Human milk or an alternative formula is the baby’s source of nutrients and energy for the first 4 to 6 months of life.  The growing consensus is that breast feeding is better for the baby’s health.  Which women are least likely to breast feed? They include mothers who work full time outside of the home, under age 25, without a high school education, African American mothers, and mothers in low- income circumstances.  Intervention – counseling focused on the benefits of breast feeding; free loan of a breast pump.  Circumstances when mothers should not breast feed: 1. Infected with AIDS or some other infectious disease that can be transmitted through her milk. 2. Active tuberculosis
  3. 3. 3. Taking any drug that may not be safe for the infant. What are some of the benefits of breast feeding? They include these benefits during the first two years of life and later:  Appropriate weight gain and lowered risk of childhood obesity.  Fewer allergies  Prevention or reduction of diarrhea, respiratory infections (such as pneumonia and bronchitis), bacterial and urinary tract infections, and otitis media (a middle ear infection).  Denser bones in childhood and adulthood.  Reduced childhood cancer and reduced incidence of breast cancer in mothers and their female offspring.  Lower incidence of SIDS  Improved neurological and cognitive development  Improved visual acuity o Malnutrition in Infancy  Marasmus: a wasting away of body tissues in the infant’s first year, caused by severe protein-calorie deficiency.  Kwashiorkor: a conditioned caused by a deficiency in protein in which the child’s abdomen and feet become swollen with water; usually appears between 1 to 3 years of age.  Toilet Training o The ability to control elimination depends on both muscular maturation and motivation. o Many toddlers are physically unable to control elimination at 2 years of age. When toilet training is initiated, it should be accomplished in a warm, relaxed, supportive manner. MOTOR DEVELOPMENT  Dynamic Systems Theory: the perspective on motor development that seeks to explain how motor behaviors are assembled for perceiving and acting. o In order to develop motor skills, infants must perceive something in the environment that motivates them to act and use their perceptions to fine-tune their movements. o When infants are motivated to do something, they create a new motor behavior to complete the new desired act. The new behavior is the result of many converging factors: 1. The development of the nervous system and the body’s physical properties, including its possibilities for movement 2. The goal the child is motivated to reach. 3. The environmental support for the skill. o Infants explore and select possible solutions to the demands of the new task; they assemble adaptive patterns by modifying their current movement patterns.  Reflexes are built-in reactions to stimuli; they govern the newborn’s movements, which are automatic and beyond the newborn’s control. o Sucking reflex – occurs when newborns automatically suck an object placed in their mouth. This enables newborns to get nourishment before they have associated a nipple with food. o Rooting reflex – occurs when the infant’s cheek is stroked or the side of the mouth is touched. In response, the infant turns his head toward the side that was touched in an apparent effort to find something to suck. o Moro reflex – a neonatal startle response that occurs in reaction to a sudden, intense noise or movement. When startled, the newborn arches its back, throws its head back, and flings out its arms and legs. Then the newborn rapidly closes its arms and legs to the center of the body. o The moro reflex is believed to be a way of grabbing for support while falling. o Grasping reflex – occurs when something touches the infant’s palms. The infant responds by grasping tightly. Reflex Stimulation Infant’s Response Developmental Pattern Blinking Babinski Grasping Moro (startle) Rooting Stepping Sucking Swimming Tonic neck Flash of light, puff of air Sole of foot stroked Palms touched Sudden stimulation, such as hearing loud noise or being dropped Cheek stroked or side of mouth touched Infant held above surface and feet lowered to touch surface Object touching mouth Infant put face down in water Infant placed on back Closes both eyes Fans out toes, twists foot in Grasps tightly Startles, arches back, throws head back, flings out arms and legs and then rapidly closes them to center of body Turns head, opens mouth, begins sucking Moves feet as if to walk Sucks automatically Makes coordinated swimming movements Forms fists with both hands and usually turns head to the right Permanent Disappears after 9 months-1 year Weakens after 3 months, disappears after 1 year Disappears after 3-4 months Disappears after 3-4 months Disappears after 3-4 months Disappears after 3-4 months Disappears after 6-7 months Disappears after 2 months  Gross Motor Skills: motor skills that involve large-muscle activities, such as walking. o The Development of Posture  Within a few weeks, can hold their heads erect, and soon they can lift their heads while prone.  By 2 months, babies can sit while supported on a lap or an infant seat  6 or 7 months, can sit independently  1st year, standing develops gradually
  4. 4.  8 months, learn to pull themselves up and hold on to a chair.  10 – 12 months, can stand alone o Learning to Walk  Walking upright requires balancing on one leg while swinging the other leg forward and simultaneously shifting the weight from one leg to the other.  If infants can produce forward stepping movements so early, why does it take them so long to learn to walk? Because the key skills in learning to walk require so many concurrent movements, infants need about a year to solve this difficult biomechanical problem. o Development in the Second Year  Become more motorically skilled and mobile. No longer content with being in a playpen, they want to move all over the place.  Pediatricians also recommend that exercise for infants should not be of the intense, aerobic variety. Babies cannot adequately stretch their bodies to achieve aerobic benefits. o Cultural Variations in Guiding Infant’s Motor Development  Jamaican mothers regularly massage their infants and stretch their arms and legs; this practice is linked to advanced motor development.  Mothers in the Gusii culture of Kenya also encourage vigorous movement in their babies.  Algonquin infants in Quebec, Canada, spend much of their first year strapped to a cradleboard.  Fine Motor Skills: motor skills that involve more finely tuned movements, such as finger dexterity. o A significant achievement in their interactions with their surroundings comes with the onset of reaching and grasping. SENSORY AND PERCEPTUAL DEVELOPMENT  What Are Sensation and Perception o Sensation: the product of interaction between information and the sensory receptors—the eyes, ears, tongue, nostrils, and skin. o Perception: the interpretation of what is sensed.  The Ecological View o Ecological view: the view that perception functions to bring organisms in contact with the environment and to increase adaptation. o Affordances: opportunities for interaction offered by objects that are necessary to perform functional activities.  Visual Perception o Visual preference method: a method used to determine whether infants can distinguish one stimulus from another by measuring the length of time they attend to different stimuli.  In Robert Fantz (1963) experiment, infants preferred to look at patterns rather than at color or brightness. Fantz used a looking chamber to study infant’s perception on stimuli. o Habituation: decreased responsiveness to a stimulus after repeated presentation of the stimulus. o Dishabituation: recovery of a habituated response after a change in stimulation. o Tracking: a technique to determine if an infant can see or hear. Newborns typically turn their eyes and heads in the direction of an interesting sound or sight, especially the human voice and face. o Equipment: videotape equipment allows the researchers to investigate elusive behaviors. o Visual perception  Visual acuity and color  Newborns cannot see small things that are far away. The newborn’s vision is estimated to be 20/600 on the well-known Snellen chart. In other words, an object 20 feet away is only as clear to the newborn as it would be if it were 600 feet away from an adult with normal vision (20/20).  By 6 months, vision is 20/100 or better, and by about the 1st birthday, the infant’s vision approximates that of an adult.  At birth, babies can distinguish between green and red. Cones are present by 2 months.  Perceiving patterns  What does the world look like to infants?  Perceptual constancy: in which sensory stimulation is changing but perception of the physical world remains constant.  Size constancy: the recognition that an object remains the same even though the retinal image of the object changes.  Shape constancy: the recognition that an object’s shape remains the same even though its orientation to us changes.  Depth perception  An important contributor to depth perception is binocular vision, which involves the fact that we have two eyes separated by several inches that give us slightly different views of the world.  Newborns do not have binocular vision; it develops at about 3 to 4 months of age.  Visual expectations  Infants not only see forms and figures at an early age but also develop expectations about future events in their world by
  5. 5. the time they are 3 months of age.  Other Senses o Hearing  During the last two months of pregnancy, the fetus can hear sounds as it nestles in its mother’s womb: It hears the mother’s voice, music, and so on. o Touch and pain  Newborns do respond to touch. o Smell  Newborns can differentiate odors. o Taste  Sensitivity to taste might be present even before birth.  Intermodal Perception: the ability to relate and integrate information from two or more sensory modalities, such as vision and hearing. o In one study, as early as 3 ½ months old, infants looked more at their mother when they also heard her voice and longer at their father when they also heard his voice. o Thus, babies are born into the world with some innate abilities to perceive relations among sensory modalities, but their intermodal abilities improve considerably through experience.  Perceptual-Motor Coupling o Locomoting in the environment teaches babies about how objects and people look from different perspectives, or whether surfaces will support their weight. Individuals perceive in order to move and move in order to perceive. Perceptual and motor development do not occur in isolation from one another but instead are coupled. REFLECTION: 1. What three pieces of advice about the infant’s physical development would you want to give a friend who has just had a baby? Why those three? 2. How much sensory stimulation should caregivers provide for infants? A little? A lot? Could an infant be given too much sensory stimulation? Explain. Reference: Santrock, J.W. (2006). Life-Span Perspective.10th Edition. McGraw-Hill. New York. Prepared by: Mrs. Maria Angela L. Diopol Instructor