Infancy: Physical Development

Growth and Stability: Physical Growth Over the first 2 years of a human’s life, growth occurs at a rapid pace.

Average birth weights (progression through the 1 st 2 years)  --By age 5 months, the average infant's birthweight has doubled to about 15 pounds.  --By age 1, the infants' birthweight has tripled to approximately 22 pounds.  --By the end of its second year, the average child weighs four times its birthweight.  --By age 1, the average baby stands 30 inches tall.  --By the end of the second year the average child is three feet tall.

At birth, the head is ¼ of the neonate’s body. By adulthood, it is only 1/8 th the size of the body. Decreasing Proportions…

 Not all parts of the body grow at the same rate. The 4 Major Principles Governing Growth The CEPHALOCAUDAL PRINCIPLE states 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 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 are later integrated into more complex skills. The PRINCIPLE OF INDEPENDENCE OF SYSTEMS suggests that different body systems grow at different rates.

Maturation Rates Different body systems mature at different rates. For instance, the nervous system is highly developed during infancy.

The nervous system comprises the brain and the nerves that extend throughout the body.  Infants are born with between 100 and 200 billion NEURONS ( 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 Neuron The basic element of the nervous system

More About Neurons… -- 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. The infant's brain is 3/4 its adult size by age two

More About Neurons… * 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).

Neuron Networks Networks of neurons become more complex over the first few years of life.

PLASTICITY is the degree to which a developing structure (e.g., the brain) or behavior is susceptible to experience The brain is relatively plastic -- Infants who grow up in severely restricted environments are likely to show differences in brain structure and weight. Brain development occurs because of genetic patterns and environmental influences.

-- 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. (brain development, continued)

Development of Body Rhythms One of the major body rhythms is an infants state -- An infant's STATE is 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 an EEG, or electroencephalogram.

The major state occupying the infant is sleep. On average, newborns sleep hours daily, ranging from hours a day. Sleep stages are fitful and "out of sync" during early infancy. By the end of the first year most infants are sleeping through the night.

The Infant’s Cycle of Sleep Infants have a cycle of sleep similar to but different than REM - RAPID EYE MOVEMENT, ( the period of sleep found in adults and children and is associated with dreaming).  Brain waves are different than the dreaming sleep of adults.  This active REM-like sleep takes up half an infants sleep at first.  Researchers think the function of REM sleep in infants is to provide a means for the brain to stimulate itself (autostimulation).

Motor Development  Basic REFLEXES, unlearned, organized, involuntary responses that occur automatically in the presence of certain stimuli, represent behavior that has survival value for the infant. swimming reflex eye blink reflex

More about reflexes in motor development… Some reflexes stay throughout life; others disappear over time. Some researchers believe reflexes stimulate the brain toward development. Reflexes are genetically determined and universal and may be remnants from the past. Reflexes can serve as helpful diagnostic tools for pediatricians because they appear and disappear on a regular timetable

Gross Motor Skills (rolling over, sitting upright, walking) By 6 months infants can move by themselves. Most can sit unsupported by 6 months Crawling appears between 8-10 months. Infants can walk holding on to furniture by 9 months and most can walk alone by 1 year.

Fine Motor Skills (coordination, sophistication) By 3 months infants can coordinate movements of limbs. Infants can grasp an object by 11 months. By age 2, infants can drink from a cup without spilling.

Milestones of Motor Development 50% of children are able to perform each skill at the month indicated, but the specific timing varies widely!

It is important to keep in mind that developmental NORMS are the average performance of a large sample of individuals of a certain age and mask substantial individual differences. (Norms are based on scales developed by developmental psychologists & pediatricians)

A common technique to determine infants’ normative standing: BRAZELTON NEONATAL BEHAVIORAL ASSESSMENT SCALE (NBAS) NBAS is a measure used to determine infants' neurological and behavioral responses to their environment. a. supplements the Apgar b. 27 categories of responses c. interactions with others d. motor behavior e. physiological control f. response to stress

More about norms Norms should be based on large, heterogeneous samples. The time at which specific motor skills appear is in part determined by cultural factors. There are certain genetic constraints on how early a skill can emerge

Nutrition in Infancy Fuels Motor Development Nutrition during infancy is extremely important. Without proper nutrition, infants cannot reach their physical potential and also may suffer cognitive and social consequences.

Malnutrition & It’s Effects Malnutrition, the condition of having an improper amount and balance of nutrients produces several results. --slower growth --susceptibility to disease --lower IQ scores

Malnutrition & It’s Effects, continued -- 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.

Risks of malnutrition are greater in underdeveloped countries and in areas with high poverty rates. Undernutrition is more common in developed countries (deficiency in the diet).

a. all essential nutrients b. natural immunity to childhood diseases c. more easily digested d. health advantages for mother (lower cancer) e. emotional advantages for both mother and child f. bonding? In spite of this, only half of mothers in U.S. breast-feed For the first four to six months of life there is no better food for an infant than breast milk! Why? Nutrition as Fuel for Motor Development: Breast or Bottle??

Breast Milk Advantages

Introducing Solid Foods  Most babies can begin to eat solid foods at about 4-6 months.  Foods are introduced gradually.  Weaning, the cessation of breast-feeding, occurs on average in the U.S. at 3-4 months.  Experts recommend infants be breast-fed for 6-12 months.

Development of the Senses Infants come to understand the world around them through sensation & perception SENSATION is the stimulation and responsiveness of the sense organs. PERCEPTION is the sorting out, interpretation, analysis, and integration of stimuli involving the sense organs and brain.

Visual Perception: Seeing the World Newborn infants cannot see beyond a distance of 20 feet. By 6 months, the average infant's vision is 20/20. Binocular vision, the ability to combine both eyes' vision to see depth and motion is achieved at 14 weeks. Gibson's "visual cliff" experiments showed that most infants between 6-14 months would not crawl over the apparent cliff. The “visual cliff” experiment examines the depth perception of infants

Infants show clear visual preferences that are present at birth  Infants prefer to look at patterns and complex stimuli.  Infants prefer to look at faces.  Minutes after birth they show a preference for certain colors, shapes, configurations May support the existence of specialized brain cells (genetic influence on visual preferences)—but environmental influences too.

Auditory Perception: The World of Sound It is clear that infants hear from the time they are born—and even before! (prenatally) Infants are more sensitive than adults to high and low frequencies but not to the middle ranges.

Sound localization permits infants to discern direction from which a sound is emanating.  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

Smell and Taste in Infancy  Infants react to unpleasant tastes and smells from birth.  Newborns can detect their mother's smell, but only when breastfed.  Infants have an innate sweet tooth.

Sensitivity to Pain and Touch Infants are born with the capacity to feel pain. Touch is one of the most highly developed sensory systems in a newborn.  The rooting reflex is strong.  Infants gain information about the world through touch.  Even the youngest infants respond to gentle touches and are calmed by them

Initially, information is collected and interpreted by individual sensory systems, but… 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)

The infants growing perceptual ability is aided by the development of affordances (action possibilities connected to a situation or stimulus).  Example: Julissa learns that her toy truck has several affordances: It can be grabbed and squeezed, chewed, thrown across the room at the cat, etc.)