2 Questions What is neoteny? What are the basic patterns of physical growth in infancy?How do genes and environment influence growth?What are the differences between individual and group growth curves?List some major milestones and range of age of acquisitionWhat are some differences in the ordering of these milestones
3 Principles of Physical Development Directionality: follows several characteristic directionsCephalocaudal
6 Principles of Physical Development Proximodistal: development from inside outMass-to-specific: gross motor skills (large muscles) develops first followed by fine motor (small muscles) skillsPrinciple of Hierarchical Integration: simple skills develop independently and are later integrated into more complex skills.Independence of Systems
10 Head circumference An index of brain size but not necessarily meaningful for individualsconcern below 3rd percentile or above 97thCan be used as a predictor of early outcome in premature infantsat birth and at one month or later corrected ageIts staying the course that its importantallowing for catch-up growthreach growth channel by months
11 Babies have big heads Newborn head is 25% of own body length Head length is 40% of mature length at birthAdult head is only ~15% of body length
12 Why?Why such large heads?Why such rapid, early growth in head size?
13 Neonteny:Mickey has a baby face Flat with small nose and cheekbonesSmall lower jawBig cranium and forehead
14 Neoteny: Holding on to infant-like characteristics Neoteny characterizes human body formBig heads and facesLarge eyesSmaller muzzleSpine attached at base of skullBrain continues growth after birthEssential constraint in human evolution
15 Neoteny characterizes human behavior Late sexual reproductionPlay and curiosity throughout life spanCultural flexibility
16 Head growth allows brain growth Rapid, decelerating growthAt birth,1 lb.15% of total body birthweight25% of final (adult’s) brain weightAt 6 months50% of final (adult’s) brain weight
17 At the same time - Myelinization Fatty sheaths develop and insulate neuronsDramatically speeding up neural conductionAllowing neural control of bodyGeneral increase in first 3 years is likely related to speedier motor and cognitive functioningallowing activities like standing and walkingEndangered by prenatal lead exposure
18 Infancy is a period of rapid, decelerating physical growth. Rapid, decelerating growth characterizesHead circumferenceBody lengthWeight
19 Height and Weight Growth During the First Two Years 10541.31533.110039.41430.99537.41328.7Boys9035.41226.5Boys8533.51124.38031.51022.0KilogramsCentimetersInches7529.5919.8Pounds7527.6817.66525.67Girls15.4Girls6023.6613.25521.7511.05019.748.84517.736.64015.724.436912151821243691215182124Age in MonthsAge in Months
20 Genes and environment Body size influenced by multiple genes each has a small effectsome do not function until after birthwhen individual differences emergeBody size influenced by environmentnutritionuterus can also constrain or promote growth
21 Genes and environment example Japanese-American infantsSmaller than European-American infantsgeneticsBut larger than Japanese national infantsdietary differencesHigher socioeconomic statusTaller, heavier kids who grow fasterProfessional 3 year olds: 1/2” tallerIn England
22 Historical increase in body size Mean height of schoolchildren increased by 0.70 cm per decadeindependent of race, sex, and age.decrease in short children (<10th percentile)
23 Rapid, decelerating growth: Length Birth length 20”add 10” by one yearadd 5” more by 2 yearsTwo year height approximately 1/2 adult heightBoys
24 Rapid, decelerating growth: Weight GirlsNewborn girl (7.25 lbs.)Gain 1.3 pounds per month for the first 6 months100% biggerDouble birth weightThen 1 pound per month through 12 months50% biggerTriple birth weightThen less than a half a pound per month through 36 months
25 Group curves Large samples Many children at a given age (e.g., 3 months)Find median (50th %ile), %se.g. at 17 months, only 5% < 75 cm.Longitudinal data may have been collectedbut at monthly intervalsWhat does individual growth in length look like?
26 Common view Individual follows continuous growth curves Portrait of group is portrait of individualBut parents report ofgrowing by leaps and boundsgrowth spurtsgrowing overnightwere dismissed
30 Growth jumps or spurts Growth occurs in spurts, jumps of almost a cm. (.9)separated by periods of no growth [stasis]of 2 to 15 daysTotal growth is sum of spurtsLonger stasis continues, more likelihood of a spurtbut spurts aperiodic
31 Saltatory growth is the rule prenatalinfantchildadolescent
35 Practical consequences Fussiness and hunger during growth periodsSleep patternsless before, more during?
36 Growth in height and weight follows a very predictable trend – unless there are extenuating factors, such as nutritional deficiencies, extreme stress, neglect, etc. Extreme neglect also affects brain development, as shown on right above.There is an interaction of biological factors and environmental factors in producing physical development—for example, effects of extremes on growth.
37 Motor DevelopmentMotor development influences and is influenced by other components of developmentIntelligence is dependent on sensorimotor activities, PiagetInstitutionalized infants – delayed motor skillsMotor activities impact emotional development, fear of heights
38 Motor development Overall patterns Individual differences Individual development
39 Norms versus Individual Differences Motor Milestones
40 Motor Development is Orderly Occurs in a specific sequenceReflexive movements (First 3-4 months): involuntary, undirected movementsPostural Reaction (approximately 2-3 months): the higher brain centers (cortex) begin functioninginhibits lower brain centerscauses primitive reflexes to disappearcoordinate movements of head, trunk and limbs so body can adjust its posture to environmentVoluntary Motor MilestonesControlled by higher brain centers (cortex)
42 Individual differences WHO Motor Development Study: Windows of achievement for six gross motor development milestones. WHO MULTICENTRE GROWTH REFERENCE STUDY GROUP.Acta Pædiatrica, 2006; Suppl 450: 86/95
43 Individual variability in locomotion BimodalityFirst WalkThelen
44 Stages in Infant Development and Feeding Birth through 6 monthsBreast milkORIron-Fortified infant formula
47 The Advantages of Breastfeeding Advantages for ChildProtects against infection—less diarrheaEnhances vaccine responseReduced risk of otitis media and respiratory infectionsDecreased risk of SIDSProtection from allergies; less eczemaHigher IQsLess risk of childhood cancer, diabetes, etc.
48 Breastfeeding Advantages for Mother Delays fertility and menstruationReduces risk of breast cancer (Am J. of Epidemiology, 1986) Breast cancer could be reduced by up to 25% through breastfeeding.Reduced risk of uterine, ovarian and endometrial cancers.Greater emotional health (less anxiety; more mutuality)Decreased osteoporosis (4 x greater in non-breastfeeders)Promotes postpartum weight loss (especially in lower body fat)
49 So, if the benefits of breastfeeding outweigh formula, why aren’t all children breastfed? InconvenientSome medications can be passed in breast milkSleep patternsExhaustion for momCan be painfulSocial tabooPumping