Infancy: Physical Development

							Infancy: Physical
  Development
Physical Growth and
   Development
           Sequences of Physical Development


• Cephalocaudal Development
   – Upper part of the head to the lower parts of the body


• Proximodistal Development
   – Trunk outward – from body’s central axis toward periphery
       What Patterns of Growth Occur in Infancy?


• Weight doubles at about 5 months; triples by first birthday


• Height increase by 50% in first year


• Infants grow 4 to 6 inches in second year; and gain 4 to 7 pounds


• Growth appears continuous but actually occurs in spurts
        Growth Curves for Weight and Height




Figure 5.1
      Changes in the Proportions of the Body




Figure 5.2
                            Reflexes


• Reflexes
  – Simple, unlearned stereotypical responses, elicited by certain
    types of stimulation

  – Survival vs. Primitive
     • Survival function
     • Neural functioning is determined by testing reflex
                              Reflexes


• Rooting
   – Baby turns head and mouth toward stimulus that strokes the cheek,
     chin, or corner of mouth
   – Facilities finding mother’s nipple for sucking


• Sucking
   – Babies will suck almost any object that touches the lips
   – Will become replaced by voluntary sucking
                             Reflexes


• Moro or startle reflex
   – Back arches, legs and arms are flung out and then brought back
     toward chest into a hugging motion
   – Elicited by loud noises or bumping the baby or sudden position
     changes

• Grasping or palmar reflex
   – Using four fingers, babies grasp fingers/objects pressed against
     the palms of their hands
   – Most babies can support their own weight
                              Reflexes


• Stepping reflex
   – Mimics walking when held under arms
   – Usually disappears by 3 or 4 months


• Babinski reflex
   – Fans or spreads toes in response to stroking foot
   – Usually disappears at end of first year


• Tonic-neck reflex
   – While lying on back, baby turns head to one side. Arm and leg on
     that side extend, while opposite side flex.
              Sensation and Perception

• Sensation: Stimulation of the sense organs.
• Perception: Interpretation of that stimulation.

• Process of integrating disjointed sensations into
  meaningful patterns through perception


• Measuring Sensation/Perception
  – Habituation/Dishabituation
                                Vision


• Visual acuity at Birth
   –   Estimate of 20/600
   –   Best see objects 7 to 9 inches from eyes
   –   Greatest gains in visual acuity between birth and 6 months
   –   By about 3 to 5 years of age, approximate adult levels


• Neonates have poor peripheral vision
   – 30 degree angle; By 7 weeks increases to 45 degrees; By 6 months of
     age, equal to adult (90 degrees)
   – Able to track movement within one day of birth
      • Preference for moving objects
                               Vision


• Visual accommodation
   – Self-adjustments made by eye lens to bring objects into focus
   – Neonates show little or no visual accommodation
      • Focus on objects 7 to 9 inches away


• Convergence
   – Does not occur until 7 or 8 weeks


• Color perception
   – At birth, cones are less well developed than rods
   – Fully mature around 3 months (Distinguish between blue/green)
   – By 4 months can distinguish between similar colors/hues
             Convergence of the Eyes




Figure 4.5
             The Looking Chamber




Figure 4.4
                         Visual Preferences


• Preferences
   – Moderately complex
   – Movement
   – Contour


• Infants prefer faces
   – Discriminate maternal and stranger faces
   – Prefer attractive faces
   – Pay most attention to edges
  Preferences for Visual Stimuli in 2-Month-Olds




Figure 5.12
      Eye Movements of 1- and 2-Month-Olds




Figure 5.13
                         Depth Perception


• Depth Perception
   – Develops around 6 months (onset of crawling)


• Research using the Visual Cliff
   – Gibson and Walk (1960)
   – Heart-rate response to determine fear
   – Relationship between crawling and fear of heights
       • Avoidance of the cliff and infants’ posture
                            Hearing

• Fetuses respond to sound
   – Can localize sound


• Startled by loud noises

• Neonates respond to amplitude and pitch

• Show preference for mothers’ voices

• Responsive to sounds and rhythms of speech
   – Capable of perceiving phonemes of other languages
   – Show no preference for specific languages
                      Hearing


• DeCasper & Spence (1986)

  – Newborns can remember and prefer a story read by
    mom during the last 6 weeks of pregnancy.
  – Exposed to 3 ½ hours of story.
   A Neonate Sucking to Hear Her Mother’s Voice




Figure 4.7
                   Development of Hearing
• By 1 month, infants perceive differences between similar speech
  sounds


• By 3½ months discriminate caregivers’ voices

• Infants perceive most speech sounds present in world languages
   – By 10 to 12 months, lose capacity to discriminate sounds not found
     in native language


• By 6 months, they can detect high frequency sounds nearly as
  well as preschoolers.


• By 6 months, they can appreciate distance.
                          Smell and Taste


• Smell
   – Well-developed at birth
   – Demonstrate aversion for noxious and preference for pleasant
     odors
       • Vanilla and Strawberry
   – Recognize familiar odors
   – Recognize mom by 6 days


• Taste
   – Sensitive to different tastes
   – Demonstrate facial expressions in response to tastes
   – Prefer sweet tastes
              Facial Expressions Elicited by
             Sweet, Sour, and Bitter Solutions




Figure 4.6
                         Touch and Pain


• Touch
   – Sensitive to touch
   – Touch elicits many reflex behaviors


• Pain
   – Past belief that neonates are not sensitive to pain
   – Neonates not cognitively equipped to ruminate about pain
      • Conditionable – distress when confronted with situation that
        previously presented itself as painful
Development of the Brain and
      Nervous System
                      What Are Neurons?


• Basic unit of nervous system
   – Receive and transmit messages


• Neurons vary according to function and location, but all contain
   – Cell Body
   – Dendrites
   – Axon


• Neurotransmitters
             Anatomy of a Neuron




Figure 5.3
                       Brain Development


• Growth Spurts in Brain Development

   – Prenatal - during 4th and 5th months
       • Proliferation of neurons


   – 25th week prenatal through end of second year after birth
       • Proliferation of dendrites and axon terminals
                  How Do Neurons Develop?

• As child matures
   – Cells grow in size and weight.
   – Axons grow in length
   – Dendrites and axon terminals proliferate
   – Connection networks become more complex
• Myelin
   – Makes messages more efficient
   – Myelination occurs with maturation
   – Inhibition of myelination results in disease
       • Multiple sclerosis
• Neurotransmitters
   – Increases during infancy.
   – Receptors continue specialization.
   Increases in Neural Connections in the Brain




Figure 5.6
                               The Brain


• Command center of organism

   – Brain of neonate weighs less than one pound
   – By first birthday, the brain triples in weight, reaching nearly 70% of
     adult weight
   Growth of Body Systems as a Percentage of
             Total Postnatal Growth




Figure 5.4
                How Do Nature and Nurture
           Affect the Development of the Brain?

• Brain development is affected by maturation (nature) and
  sensory stimulation and motor activity (nurture)

   – Rats in enriched environment
       • More synapses per neuron
   – Human infants have more neural connections than adults
       • If activated by experience, connection survives
       • If not activated, connection does not survive
   – Adequate nutrition is necessary
                 Nutritional Needs of Children


• Infants require breast milk or iron fortified formula


• Solid foods may be introduced about 4 to 6 months
    – Iron-enriched cereal, strained fruits, vegetables, and meats


• Whole cow’s milk delayed until 9 to 12 months
Why Do Women Bottle-feed or Breastfeed their Children?


• Choice to breastfeed is influenced by
   – Domestic and occupational arrangements
   – Attitudes regarding benefits for bonding and infant health
   – Fear of pain, unease with breastfeeding, and public breastfeeding
   – Community and familial support
   – Level of education


• Colostrum early form of breast milk
   – High level of nutrients into low volume
                   Advantages of Breast Milk


• Some advantages of breast milk

   – Conforms to digestion process
   – Possesses needed nutrients
   – Contains mother’s antibodies
   – Protects against childhood lymphoma, ear infections, etc.
   – Helps protect against infant diarrhea
   – Is less likely than formula to cause allergies
   – Helps prevent obesity later in life
   – Maternal health benefits
   – Human newborns prefer it
                Disadvantages of Breast Milk


• Disadvantages of breast milk
   – HIV, alcohol, drugs, and environmental hazards may be transmitted
     through breast milk
   – Mother must be adequately nourished
   – Physical demands on mother


• What about mothers who smoke?
   – No harmful effects on infants have been noted
Motor Development
                What Is Motor Development?


• Developments in the activity of muscles, and changes in posture,
  movement, and coordination
• Follows cephalocaudal and proximodistal patterns
   – Lifting and holding head before torso
   – Voluntary reaching
   – Locomotion
       • Sequence – Rolling over, sitting, crawling, creeping, walking,
         running
                      Control of the Hands


• Newborns track objects with eyes but do not reach for them
• Grasp reflex
   – Grasp but do not release intentionally


• Voluntary grasping
   – Ulnar grasp
   – Pincer grasp


• Visual – motor coordination
             Pincer Grasp




Figure 5.7
                            Locomotion


• Moving from one place to another
• Sequence with variation in ages of initiation
   – Roll over, sit, crawl, creep, walk (supported and unaided)
• Muscle strength, density of bones, balance, and coordination
  improve
   – Climb steps, run, walk backward, kick a ball, jump
             Motor Development in Infancy




Figure 5.8
             Creeping




Figure 5.9
              Walking




Figure 5.10
        What Are the Roles of Nature and Nurture
                in Motor Development?

• Maturation (nature)
   – Myelination and differentiation is needed for certain voluntary motor
     activities


• Experience (nurture)
   – Experimentation to achieve milestones
   – Slight effect in training to accelerate motor skills


• Reaction range
   – Limits for the expression of inherited traits
              Native American Hopi Infant
              Strapped to a Cradle Board




Figure 5.11