Lifespan overheads, chapter 4: physical development in infancy & toddlerhood 1 Chapter 4: Physical Development in Infancy and Toddlerhood Body Growth body size and muscle/fat o by the end of 1st year, height increases by 50% o by 2 years old, height increases by 75% o by 5 months weight has doubled o at 1 year weight has tripled o at 2 years weight has quadrupled o “baby fat” peaks around 9 months o muscle tissue develops slowly Individual and group differences o In infancy girls are slightly shorter and lighter and have a higher ratio of fat to muscle than boys. o Some children just grow more quickly than others. o skeletal age: X-raying the long bones of the body to see the extent to which cartilage has hardened into bone o African-American children are slightly ahead of Caucasian children at all ages o girls are considerably ahead of boys body proportions o cephalocaudal trend: at birth, the head is ¼ of total body length yy age 2 the head is 1/5 of body length o proximodistal trend: head, chest, and trunk arms and legs hands and feet Brain Development neurons o 100 to 200 billion neurons (nerve cells). o Synapses: spaces between adjacent neurons o By end of 2nd trimester, production of neurons is over o After birth, they start to form synaptic connections o synaptic pruning o Neurons that get stimulated establish new synapses o glial cells create myelin sheaths; multiply rapidly from the 4th month of pregnancy through the 2 nd year of life. Lifespan overheads, chapter 4: physical development in infancy & toddlerhood 2 the cerebral cortex o accounts for 85% of the brain’s weight, contains the most neurons. o last part of the brain to stop growing o different regions have specific functions Frontal Lobe: motor control, executive functions One of the last regions to develop. It will not finish growing until the early 20s! Parietal Lobe: controlling incoming sensory information Occipital Lobe: handles visual information Temporal Lobe: auditory information is processed o lateralization of the cortex: LEFT spontaneous language complex movement memory for words, numbers anxiety, positive emotions RIGHT memory for music memory for geometric patterns face recognition negative emotions o may be reversed in left-handed people o Most newborns show greater activity in the LH when listening to speech, whereas the RH reacts more to non- speech sounds and stimuli that cause a negative emotion o Plastic brain! still adaptable. If a part of the brain is damaged, other parts will take over the tasks. Once lateralization is complete (age 8-10), the brain is less able to adapt to damage Lifespan overheads, chapter 4: physical development in infancy & toddlerhood 3 brain growth spurts and sensitive periods: o sensory deprivation research keep a month-old kitten in the dark for 3 or 4 days, visual areas of the brain degenerate. 2 months in the dark: damage is permanent severe stimulus deprivation affects overall brain growth. o intermittent growth spurts in the brain from infancy to early adulthood 1st year of life: 3-4 months, when they begin to reach 8 months, when they begin to crawl 12 months, when they begin to walk 1 ½ and 2 years, when they start to use language what “wires” a kid’s brain during these periods is experience impoverished environments threaten this development. so does overwhelming the child with expectations beyond their current capacities o states of arousal: By 2, the child is sleeping 12 to 13 hours a day, but most of the sleep happens in one extended period, with maybe one or 2 naps during the day once the baby is in the middle of their first year, the brain secretes more melatonin at night than during the day Lifespan overheads, chapter 4: physical development in infancy & toddlerhood 4 Influences on early physical growth heredity nutrition o Breast versus bottle feeding: 2/3 of North American mothers breast feed Breast fed babies in poverty-stricken nations are less likely to be malnourished; 6 to 14 times more likely to survive the first year of life mother is less likely to get pregnant while nursing breast and bottle fed youngsters in industrialized nations do not differ in intelligence or emotional adjustment o chubby babies: infants and toddlers can eat nutritious foods freely, without risk of becoming too fat malnutrition: o 40 to 60% of the world’s children are malnourished o In the US, 12% of children are malnourished o Globally 4 to 7% are severely affected Marasmus Kwashiorkor Emotional Well-Being Nonorganic failure to thrive Learning capacities Learning: changes in behaviour as a result of experience. classical conditioning: o Helps babies recognize which events usually occur together in the everyday world, so they can anticipate what is about to happen next. Nursing + stroking sucking Stroking sucking Lifespan overheads, chapter 4: physical development in infancy & toddlerhood 5 operant conditioning: o In the early weeks of life, infants’ behaviours like sucking and head turning can be conditioned in this way. o E.g. using special pacifiers to study preferences o E.g. the mobile study Habituation and dishabituation: o habituation is the gradual reduction in the strength of a response due to repetitive stimulation o dishabituation: responsiveness returns to a high level when the stimulus is changed imitation: newborns have a primitive ability to learn through imitation. Infants as young as 2 days old can imitate a variety of facial expressions. o primitive reflex? o newborns imitate many facial expressions even after short delays; suggests that the behavior is voluntary Motor Development Gross motor development: control over actions that help infants get around in the environment (crawling, standing, walking). Fine motor development: smaller movements, like reaching, grasping. cephalocaudal trend: motor control of the head comes before control of arms and trunk, which come before control of legs. proximodistal trend: head, trunk, and arm control happen before coordination of hands and fingers. Each new skill is a joint product of: 1) the CNS 2) movement possibilities for the body 3) environmental supports for the skill 4) the goal the child has, like getting a toy or crossing the room Lifespan overheads, chapter 4: physical development in infancy & toddlerhood 6 Fine motor development: reaching opens up a whole new way to explore the environment o Newborns make poorly coordinated swipes at objects, called prereaching; drops away at around 7 weeks. o At 3 months, voluntary reaching appears and improves o Once babies can reach, they start to modify their grasp. A newborn’s grasp reflex is replaced by the ulnar grasp: fingers closing against the palm. By end of 1st year, use the thumb and forefinger in the pincer grasp. Perceptual Development Perception: the ability to organize and interpret incoming sensations. hearing: o 3 days old: turn eyes and head in direction of a sound. o can detect almost all sounds in human languages at birth o by 6 months old they screen out sounds that are not useful in their own language. o second half of the 1st year, recognize familiar words in spoken language o 7 to 10 month olds preferred speech with natural breaks to speech with pauses in unnatural places. vision: By 2 months, babies can focus on objects and discriminate colours as well as adults can. o Visual acuity improves steadily (20/600 at birth; to 20/100 by 6 months; 20/20 at 11 months) o Depth perception: ability to judge the distance of objects from one another and from ourselves. visual cliff (Gibson & Walk, 1960):crawling babies cross the shallow side but react with fear to the deep side precrawlers’ abilities to use other cues to depth: Motion Binocular cues Pictorial cues Lifespan overheads, chapter 4: physical development in infancy & toddlerhood 7 independent movement and depth perception: the more experience a baby has crawling, the better their depth perception, memory for object locations o pattern and face perception: newborns prefer to look at patterned rather than plain stimuli 3-week old infants look longest at black and white checkerboards with few squares, whereas 8 and 14 week olds prefer those with many squares When shown a picture of a human face, 1-month olds limit their visual exploration to the border of the stimulus. By 2 months, they thoroughly explore the internal features of a pattern By 4 months, they even see subjective boundaries that aren’t there! By 2-3 months, they prefer faces to other similar configurations by 3 months, they can make fine distinctions among the features of different faces. By 7 to 10 months they consistently treat positive faces as different from negative ones o Intermodal perception: Newborns turn in the general direction of a sound Pacifier study 3-4 month old babies can relate a child’s or adult’s moving lips to the corresponding sounds in speech by 7 months, can link a happy or angry voice with the appropriate face of a speaking person Understanding perceptual development Eleanor & James Gibson’s differentiation theory: a built-in tendency to search for order and consistency, a capacity that gets more fine-tuned with age. We learn to get better at differentiating the features of various objects and patterns. An alternative view: babies impose meaning on what they perceive, constructing categories of objects and events in the surrounding environment.