Chapter 5- The First Two Years:Biosocial Development

Body Changes• Average weight: double the birthweight by

month 4, triple it by age 1, much of it is fat• Average height: grow 14 inches from birth to

age 2 • These numbers are norms, an average

measurement.

Body ChangesBody Size

• Head-sparing- biological mechanism that protects the brain when malnutrition disrupts body growth. – The brain is the last part of the body to be

damaged by malnutrition.

• Percentile- point on a ranking scale of 0 to 100. – 50th percentile is the midpoint with ½ the sample

being higher and ½ lower.

Sleep

• Average newborn sleeps 16 hours per day

• Specifics vary due to age, characteristics, and social environment

• Ample sleep correlates with normal brain maturation, learning, emotional regulation, academic success and psychological adjustment

Sleep

• REM Sleep: Rapid eye movement sleep,

dreaming, rapid brain waves

• Slow-wave sleep: quiet sleep, increases at 3-4 months

• Co-sleeping: custom of parents and children sleeping in same room, more common in Asia, Africa and Latin America than in Western cultures

Brain Development

• Neuron- the billions of nerve cells in the central nervous system.

• Cortex- the outer layers of the brain.• Axon- a fiber that extends from a

neuron and transmits electrochemical impulses from that neuron to the dendrites of other neurons.

Brain Development

• Dendrite- a fiber that extends from a neuron and receives electrochemical impulses transmitted from other neurons via their axons.

• Synapse- the intersection between the axon of one neuron and the dendrites of other neurons.

• Neurotransmitter- a brain chemical that carries information from the axon of a sending neuron to the dendrites of a receiving neuron.

Brain Development

Transient Exuberance

• The great but temporary increase in the number of dendrites in an infant’s brain from birth to age 2

• Enables neurons to connect and communicate with other neurons

• This is followed by pruning where unused neurons and misconnected dendrites die

Stress and the Brain

• If it produces too many stress hormones in infants, the brain will not be able to have normal stress responses.

• Occurs in infants who are terrified and experience other forms of stress.

• Can continue to occur when the infant is an adult

Necessary and Possible Experiences

Experience-related aspects of brain function:

• Experience-expectant : require basic common experiences in to develop normally (i.e. people who love them)

• Experience-dependent: these happen to some infants but not all, not necessary for brain function (i.e. language baby hears)

Brain Development

• prefrontal cortex: the area for anticipation, planning, and impulse control

• Shaken baby syndrome- a life-threatening injury occurring when an infant is forcefully shaken back and forth, rupturing blood vessels and breaking neural connections .

• Self-righting- inborn drive to fix a developmental deficit– All people have self-righting impulses for physical

and emotional imbalances.

Sensation and Movement

• Sensation- The response of a sensory system (eyes, ears, skin, tongue, nose) when it detects a stimulus.

• Perception- The mental processing of sensory information when the brain interprets a sensation.

• Sensory development- typically precedes intellectual and motor development

Sensation and Movement

Hearing develops during the last trimester of pregnancy and is already quite acute at birth; the most advanced of the newborn’s senses.

Vision is the least mature sense at birth. – Newborns focus only on objects between 4

and 30 inches away.– Binocular vision, the ability to coordinate the

two eyes to see one image, appears at 3 months.

Smelling, Tasting, and Touching

• Function at birth and adapt to social world

• Babies recognize each person’s smell and handling

• Basic Infant Care differs by culture– Massage important in some cultures

• Infant senses function to help babies join the human family

Sensation and Movement

• Gross motor skills- Physical abilities involving large body movements, such as walking and jumping.

• Fine motor skills- Physical abilities involving small body movements, especially of the hands and fingers, such as drawing and picking up a coin.

Gross Motor Skills

Ethnic Variations

• Gene differences in different ethnic groups

• Cultural patterns of child rearing affect sensation, perception, and motor skills

Surviving in Good Health

• About 10 billion babies were born 1950-2010 worldwide

• More than 2 billion died before age 5

• Immunization has saved many people– The risks of diseases are far greater than the

risk from immunization.

Surviving in Good Health

Surviving in Good Health

Surviving in Good HealthNutrition

• For every infant disease (including SIDS), breast-feeding reduces risk and malnutrition increases it.

• Breastfed babies are less likely to develop allergies, asthma, obesity, and heart disease.

• As the infant gets older, the composition of breast milk adjusts to the baby’s changing nutritional needs.

Malnutrition

• Protein-calorie: when not enough food of any kind is consumed

• Stunting: being too short for your age due to severe and chronic malnutrition

• Wasting: being very underweight due to malnutrition

Malnutrition

• Marasmus: severe malnutrition during infancy where child stops growing, tissues waste away and then usually dies

• Kwashiorkor: disease of chronic malnutrition during childhood where child becomes more likely to get other diseases such as measles, diarrhea and influenza