Infancy: Physical Development. Chapter 4 Development Across the Life Span. Growth and Stability: Physical Growth. Over the first 2 years of a human’s life, growth occurs at a rapid pace!. Height & Weight Growth.
Development Across the Life Span
The greatest height & weight increases occur during the 1st year of life, but children continue to grow through infancy & toddlerhood.
--By age 5 months, the average infant's birthweight has doubled to about 15 pounds.
(progression through the 1st 2 years)
At birth, the head is ¼ of the neonate’s body. By adulthood, it is only 1/8th the size of the body.
1) The CEPHALOCAUDAL PRINCIPLEstates that growth follows a pattern that begins with the head and upper body parts and then proceeds to the rest of the body.
2) The PROXIMODISTAL PRINCIPLEstates that development proceeds from the center of the body outward.
3) The PRINCIPLE OF HIERARCHICAL INTEGRATIONstates that simple skills typically develop separately and independently but are later integrated into more complex skills.
4) The PRINCIPLE OF INDEPENDENCE OF SYSTEMSsuggests that different body systems grow at different rates.
Different body systems mature at different rates.
For instance, the nervous system is highly developed during infancy.
Infants are born with between 100 and 200 billionNEURONS! (the nerve cells of the nervous system).
As the infant's experience in the world increases, neurons that do not become interconnected become unnecessary and die off.
The basic element of the nervous system
-- Neurons increase in size.
-- Neurons become coated with MYELIN,a fatty substance that helps insulate neurons and speeds transmission of nerve impulses.
-- The brain is made up of neurons, and triples its weight in the first two years of life.
* As they grow, neurons become arranged by function.
* Some move into the CEREBRAL CORTEX,the upper layer of the brain.
* Others move to subcortical levels, which regulate fundamental activities such as breathing and heart rate (and are below the cerebral cortex).
Networks of neurons become more complex over the first few years of life.
Brain development occurs because of genetic patterns and environmental influences.
The brain is relatively plastic
-- Infants who grow up in severely restricted environments are likely to show differences in brain structure and weight.
-- Research with non-humans reveals that a SENSITIVE PERIOD exists which is a specific but limited time span, usually early in an organism's life, during which the organism is particularly susceptible to environmental influences relating to some particular facet of development.
*Some are apparent right after birth, others emerge over the course of the 1st year as the nervous system becomes more integrated
-- An infant's STATEis the degree of awareness it displays to both internal and external stimulation.
-- Includes various levels of wakeful behaviors (alertness, crying, etc.) and various levels of sleep (active, quiet)
-- Changes in state are reflected in brain waves measured by a device called anEEG, or electroencephalogram.
REM sleep increases & the total amount of sleep falls as we age.
US rates have dropped 38% since 1992 as parents have learned to have babies sleep on their backs.
Basic REFLEXES,unlearned, organized, involuntary responses that occur automatically in the presence of certain stimuli, represent behavior that has survival value for the infant.
50% of children are able to perform each skill at the month indicated, but the specific timing varies widely!
(Norms are based on scales developed by developmental psychologists & pediatricians)
BRAZELTON NEONATAL BEHAVIORAL ASSESSMENT SCALE (NBAS)
Nutrition during infancy is extremely important! Without proper nutrition, infants cannot reach their physical potential and also may suffer cognitive and social consequences.
In developing countries, the number of underweight children under age 5 is substantial.
Malnutrition, the condition of having an improper amount and balance of nutrients produces several results.
--susceptibility to disease
--lower IQ scores
--Malnutrition can also cause MARASMUS,a disease characterized by the cessation of growth in infants.
--Older children are susceptible to KWASHIORKOR,a disease in which a child's stomach, limbs, and face swell with water.
Single-parent and minority families are more likely to have kids under age 3 living in poverty.
Nutrition as Fuel for Motor Development: Breast or Bottle??
In spite of this, only half of mothers in U.S. breast-feed
Most babies can begin to eat solid foods at about 4-6 months.
Experts recommend infants be breast-fed for 6-12 months.
Infants come to understand the world around them through sensation & perception
Binocular vision, the ability to combine both eyes' vision to see depth and motion is achieved at 14 weeks.
May support the existence of specialized brain cells (genetic influence on visual preferences)—but environmental influences too!
In a classic experiment, Robert Fantz found that 2- and 3-month-old infants preferred to look at more complex stimuli.
--This skill is poorer in infants than adults because of infants' smaller heads.
--It reaches adult level at 1 year.
--Infants can differentiate changes in melodies and sounds - a requirement for language - and their mother's voice from other voices
The weight gain of premature infants who were systematically massaged is greater than those who did not receive the massage!
Knowing what we know about pain & touch…
-Risks: infection, irritation, bleeding, reduced sexual pleasure
-Minor benefits: slightly lower risk of urinary track infections
~Cultural & psychological issues involved in decision!
Eventually infants use the MULTIMODAL APPROACH TO PERCEPTION in which information collected by various individual sensory systems is integrated and coordinated.
This approach is evidence of the sophisticated perceptual abilities of infants (combining sensory inputs!)