Chapter 4: Physical Development in Infancy Life-Span Development Twelfth Edition Chapter 4: Physical Development in Infancy ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Patterns of Growth: Cephalocaudal Pattern: sequence in which the earliest growth always occurs from the top downward Also applies to gains in motor development Proximodistal Pattern: sequence in which growth starts in the center of the body and moves toward the extremities ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Height and Weight: Average North American newborn is 20 inches long and 7 ½ pounds 95% of full-term newborns are 18-22 inches long and weigh between 5 ½ and 10 lbs. Newborns lose 5-7% of their body weight in the first few days of life They typically gain 5-6 ounces per week during the first month Weight usually triples by their 1st birthday Newborns gain approximately 1 inch per month during the first year Growth slows considerably during the 2nd year ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. The Brain: Brain continues developing past infancy Shaken Baby Syndrome: brain swelling and hemorrhaging from child abuse trauma Brain imaging technologies cannot typically be used with babies EEGs show regular spurts in the brain’s electrical activity Spurts may coincide with important changes in cognitive development At birth, the brain is 25% of its adult weight; at 2 years of age, it is 75% of its adult weight The brain does not mature uniformly ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Forebrain: portion of the brain farthest from the spinal cord; includes cerebral cortex Cerebral Cortex: folded surface covering the forebrain Cerebral cortex is divided into 2 hemispheres, each with 4 lobes Frontal lobe: voluntary movement, thinking, personality, and intentionality Occipital lobe: vision functions Temporal lobe: hearing, language processing, and memory Parietal lobe: spatial location, attention, and motor control ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Lateralization: specialization of function in one hemisphere of the cerebral cortex or the other Some functions are lateralized, some are not Complex functions involve communication between both hemispheres ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Neurons: brain nerve cells that communicate through electrical and chemical signals Axons carry signals away from the cell body Dendrites carry signals toward the cell body Myelin sheath is a layer of fat cells that insulate axons Helps electrical signals travel faster Terminal buttons release chemicals (neurotransmitters) into synapses Synapses: tiny gaps between neurons ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Changes in Neurons: Myelination: the process of encasing axons with fat cells Begins prenatally and continues into adolescence Connectivity among neurons increases New dendrites grow Connections among dendrites increase Synaptic connections increase More synaptic connections are created than will ever be used Leads to a “pruning” of unused connections ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Changes in regions of the brain: “Blooming and pruning” of synapses varies by brain region Pace of myelination varies as well ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Depressed brain activity has been found in children who grow up in a deprived environment Enriched environments promote faster brain development than deprived ones After birth: sights, sounds, smells, touches, language, and eye contact help shape the brain’s neural connections Repeated experience wires (and rewires) the brain Brain is both flexible and resilient ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Typical newborns sleep 16-17 hours per day Infants vary in their preferred times for sleeping Most have moved closer to adult-like sleep patterns by 4 months of age Factors involved in night waking: Daytime crying and fussing Distress when separated from mother Breast feeding Co-sleeping ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Cultural variations influence infant sleeping patterns Babies average much more REM sleep than do older children or adults REM sleep may provide infants with added self-stimulation REM sleep may also promote brain development We do not know whether infants dream or not ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. The practice of shared sleeping, in which a newborn shares a bed with mother, varies among cultures Potential benefits: Promotes breast feeding and a quicker response to crying Allows mother to detect potentially dangerous breathing pauses in baby American Academy of Pediatrics discourages shared sleeping Increases risk of injury (rolling over baby) and SIDS ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. SIDS (Sudden Infant Death Syndrome): infants stop breathing and die without apparent cause Highest cause of infant death in U.S. annually Highest risk is 2-4 months of age Risk decreases when infant sleeps on its back and when a pacifier is used ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Other risk factors associated with SIDS: Siblings who died from SIDS Sleep apnea or low birth weight Infants passively exposed to cigarette smoke Being from lower SES or being African American or Eskimo Infants placed in soft bedding Infants with abnormal brain stem functioning involving serotonin ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Experts recommend that infants consume 50 calories per day for each pound they weigh U.S. parents typically do not feed infants enough fruits and vegetables By 15 months, French fries are the most common vegetable eaten Increasing rates of overweight and obese infants Other factors: Mother’s weight gain during pregnancy and pre-pregnancy weight Breast feeding vs. bottle feeding ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. American Academy of Pediatrics strongly endorses breast feeding throughout the first year Benefits for baby can include: Fewer gastrointestinal and lower respiratory tract infections Potentially decreased risk of asthma Less likely to become overweight or obese Less incidence of diabetes Less likely to experience SIDS ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Benefits for mother can include: Lower incidence of breast and ovarian cancer Lower incidence of Type 2 diabetes Breast feeding does not: Help mother return to pre-pregnancy weight Guard against osteoporosis Decrease likelihood of experiencing post-partum depression ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Women less likely to breast feed: Mothers who work full-time outside of the home Mothers under age 25 Mothers without a high school education African-American mothers Mothers in low-income circumstances ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Mother should not breast feed if: She has AIDS or other infectious diseases that can be transmitted through milk She has active tuberculosis She is taking a drug that may not be safe for the infant No psychological differences have been found between breast-fed and bottle-fed infants Most breast- vs. bottle-feeding studies are correlational and do not imply causation ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Dynamic Systems View: Infants assemble motor skills for perceiving and acting Motor skills represent solutions to goals Development is an active process in which nature and nurture work together Development of nervous system Body’s physical properties and possibilities for movement Goal the child is motivated to reach Environmental support for the skill ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Reflexes: built-in reactions to stimuli; generally carry survival mechanisms Rooting Reflex: when the infant’s cheek is stroked, the infant will turn its head to the side that was touched Moro Reflex: automatic arching of back and wrapping of arms to center of body when startled Grasping Reflex: infant’s hands close around anything that touches the palms Some reflexes continue throughout life; others disappear several months after birth ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Gross Motor Skills: skills that involve large-muscle activities Walking, grabbing for objects Gross motor skills require postural control Posture is a dynamic process linked with sensory information in the skin, joints, and muscles Infants can produce stepping movements needed for walking from a very early age They lack the ability to stabilize balance on one leg at a time Infants learn what kinds of places and surfaces are safe for locomotion ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Development in the 2nd Year: Toddlers become more skilled and mobile Motor activity is vital to the child’s development of competence and independence By 18-24 months, toddlers can: Walk quickly or run stiffly Balance on their feet in a squat position Walk backward Stand and kick a ball without falling Jump in place ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Cultural Variations: mothers in developing countries tend to stimulate their infants’ motor skills more than mothers in more modern countries Infants can reach motor milestones slightly earlier if provided with physical guidance or given opportunities for exercise Even when activity is restricted, many infants still reach milestones at a normal age ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Fine Motor Skills: involve finely tuned movements Reaching and grasping is a significant milestone for infants Palmer grasp: grasping with the whole hand Pincer grip: grasping with the thumb and forefinger Perceptual-motor coupling is necessary for infants to coordinate grasping Experienced infants look at objects longer, reach for them more, and are more likely to mouth the objects ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Sensation: occurs when information interacts with sensory receptors (eyes, ears, tongue, nostrils, and skin) Perception: the interpretation of what is sensed Ecological View: we directly perceive information that exists in the world around us The perceptual system selects from the rich information provided by the environment Perception enables interaction with, and adaptation to, one’s environment ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Visual Preference Method: infants look at different things for different lengths of time They look at preferred objects longer Habituation: decreased responsiveness to a stimulus after repeated presentations Dishabituation: recovery of a habituated response after a change in stimulation ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Newborn’s vision is about 20/600 (an object 20 feet away appears as if it were 600 feet away) By the age of 6 months, vision is 20/100 or better Vision approximates that of an adult by the infant’s first birthday Infants show an interest in human faces soon after birth The way they gather information about the visual world changes rapidly with age ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Eleanor Gibson and Richard Walk studied development of depth perception using a “visual cliff” Infants 6-12 months old can distinguish depth Infants 2-4 months old show heart rate difference when placed on deep side of cliff Infants develop binocular depth cues by about 3-4 months of age ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Fetuses can hear and learn sounds during the last two months of pregnancy and can recognize their mother’s voice at birth Newborns: Cannot hear soft sounds as well as adults Are less sensitive to pitch Are fairly good at determining the location of a sound ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Touch and Pain: newborns respond to touch and can feel pain Smell: newborns can differentiate odors Preference for mother’s smell by 6 days Taste: sensitivity to taste may be present before birth ©2009 The McGraw-Hill Companies, Inc. All rights reserved.

©2009 The McGraw-Hill Companies, Inc. All rights reserved. Intermodal Perception: the ability to integrate information from two or more sensory modalities Babies are born with some innate abilities to perceive relations among senses Their abilities improve considerably through experience Perceptual–Motor Coupling: action guides perception, and perception guides action ©2009 The McGraw-Hill Companies, Inc. All rights reserved.