Infants grow rapidly in the first 2 years, with the greatest amount of growth occurring during the first year.
Birthweight
By 5 months, birthweight has doubled
By 1 year, birthweight has tripled
By end of second year, birthweight has quadrupled
Length
By end of year 1, average baby is 30 inches tall
By end of year 2, child is 3 feet tall
Not all parts grow at same rate (head)
Length of a newborn is 19” (average).
By the end of 1st year, baby is 30” tall (average).
By the end of 2nd year, baby is 3 feet tall! (average).
• The cephalocaudal principle states that growth follows a direction and pattern that begins with the head and upper body parts and then proceeds to the rest of the body.
• The proximodistal principle states that development proceeds from the center of the body outward.
• The principle of hierarchical integration states that simple skills typically develop separately and independently, but that these simple skills are integrated into more complex ones.
• The principle of the independence of systems suggests that different body systems grow at different rates.
Nervous system is brain and nerves
Neurons
Infants born with 100 and 200 billion neurons
Dendrites receive messages; Axons: Send messages to other neurons
Communication between cells is chemical and uses neurotransmitters through synapse
Synaptic Pruning: Cells that are not needed die off
Neurons increase in size
Axons become coated with myelin
Myelin: Fatty substance that protects and speeds transmission of nerve impulses
Brain triples its weight in the first 2 years of life
Neurons become arranged by function
Some move to cerebral cortex, the upper layer of brain
Some go to subcortical levels, where they regulate basic function
Plasticity, sensitive period
Rhythms and States
Rhythms: Repetitive, cyclical patterns of behavior
States: The degree of awareness an infant displays to both internal and external stimulation
Sleep: Perchance to Dream?
Newborns sleep 16 to 17 hours daily (10-20)
Sleep stages are fitful and “out of sync” during early infancy
Most do not sleep through the night for several months
Rapid eye movement (REM) is associated with dreaming
Infant brain waves are different than the dreaming sleep of adults
This active REM-like sleep takes up half of infant’s sleep
Autostimulation is the brain stimulating itself
SIDS: The Unanticipated Killer
Sudden infant death syndrome (SIDS): Unexplained death of a seemingly healthy baby
Affects about 2,500 infants in the United States every year
No cause has been found
Leading cause of death in the first year of life
“Back-to-sleep” guidelines have decreased incidence of SIDS
The Basic Reflexes
Reflexes are unlearned, organized, involuntary responses that occur automatically in the presence of certain stimuli.
Swimming reflex
Eye-blink reflex
Some reflexes stay throughout life, others disappear
Babinski, Moro, rooting, grasping, startle
By 6 months, infants can move by themselves
Crawling between 8 and 10 months
Support themselves on furniture and walking by 9 months
Walk alone by 1 year
Most sit unsupported by 6 months
Fine Motor Skills
By 3 months, infants coordinate movements of limbs
Grasp objects by 11 months
By age 2, drink from cup without spilling
Motor skill development follows a sequential pattern
Simple skills are added to more sophisticated ones
As infants get older, they use pincer grasp: thumb and index finer meet to form a circle
Sensation: The stimulation of sense organs
Perception: Our interpretation and analysis of a sensory stimulus
Visual Perception
Newborns can’t see beyond 20 feet
By 6 months, the average infant’s vision is 20/20
Depth perception develops at 6 months
Infants prefer patterns and complex stimuli
Infants prefer to look at faces
Auditory – begins prenatally, sensitive high and low pitch, sound localization compares to adults at 1 yr
Smell/Taste – react to unpleasant taste/smell from birth, recognize mothers smell when breastfed, prefer sweet
Pain – sensitive at birth (circumcision?)
Touch/tactile – most highly developed sense
