Psych Ch. 5: Physical Development In Infancy and Childhood

Parts of the body grow at different rates, in two growth patterns:

Cephalocaudal and Proximodistal

Cephalocaudal trend of growth

the head develops more rapidly than the lower body, and by age two the lower portion of the body catches up (“from top to bottom”)

Proximodistal trend of growth

growth proceeds from the center of the body outwards (“from the inside out”)

Growth norms

height and weight averages for children of the same age

skeletal age

the best estimate of a child’s physical maturity. Done by measuring bone density/development

neurons

nerve cells that store and transmit information

synapses

tiny gaps between neurons

neurotransmitters

chemicals released by neurons that send messages across synapses

the process of brain growth

• programmed cell death makes space for neural fibers and synapses

• stimulation is vital to the survival of neurons

• synaptic pruning returns neurons to an uncommitted state to support future development

Glial cells

• make up about half of the brain’s volume

• multiply rapidly from fourth month of pregnancy through second year of life

myelination

coating of neural fibers with myelin, an insulating fatty sheath

brain development is jointly influenced by…

genetically programmed events and the child’s experiences

electroencephalogram (EEG)

used to examine brain-wave patterns for stability and organization

Event-related potentials (ERPs)

used to detect general location of brain wave activity

Neuroimaging techniques that provide more precise information:

• Position emission tomography (PET)

• Functional Magnetic Resonance Imaging (fMRI)

• Near-infrare spectroscopy (NIRS)

Limitations of measures of brain functioning

• PET requires injection of radioactive substance

• PET and fMRI require subject to remain motionless (not suitable for young children)

• NIRS only examines the functioning of the cerebral cortex (observations and self-reports are needed to help clarify relationships between a stimulus and the pattern of the brain activity produced)

Cerebral cortex

• largest brain structure, containing 20 billion neurons

• sensitive to environmental influences for a much longer period than any other part of the brain

frontal lobes

cortical regions with the most extended period of development

prefrontal cortex

• lies in the front of areas controlling the body

• responsible for complex thought

• undergoes rapid growth during preschool and school years, and again in adolescence

lateralization

specialization of the brain’s two hemispheres (the two hemispheres of the cerebral cortex differ in their motor, cognitive, and emotional functions

left hemisphere

in most people, responsible for verbal activities and positive emotion

right hemisphere

handles spatial abilities and negative emotion

brain plasticity depends on…

the timing of lateralization

benefits of breastfeeding

• ideally suited to infants’ needs

• provides some protection against respiratory and intestinal infections

• helps increase spacing among siblings

reducing the risk of obesity:

• breastfeed for the first six months

• avoid giving babies unhealthy foods

• provide toddlers with opportunities for energetic play

marasmus

caused by diet low in all essential nutrients

kwashiorkor

caused by an unbalanced diet very low in protein

iron-deficiency anemia

affects up to half of children younger than age 5 wordwide

Classical conditioning

• made possible by infant reflexes

• requires an unconditioned stimulus (UCS) to consistently reproduce an unconditioned, or reflexive, response (UCR)

• neutral stimulus is presented just before or at the same time as the unconditioned stimulus

• if learning occurs, neutral stimulus alone - now a conditioned stimulus (CS) will produce a response similar to the reflexive response, now a conditioned response (CR)

operant conditioning

• infants operate on the environment

• stimuli that follow their behavior change the probability that the behavior will occur again

• plays a vital role in the formation of social relationships

• reinforcer: stimulus that increases the occurrence of a response

• punishment: removing a desirable stimulus or presenting an unpleasant one to decrease the occurrence of a response

habituation

gradual reduction in the strength of a response due to repetitive stimulation

recovery

return to a high level of responsiveness when a new stimulus is introduced

novelty preference

• recovery to a new stimulus

• assesses recent memory

familiarity preference

• recovery to a familiar stimulus

• assesses remote memory

statistical learning

the ability to detect fundamental structure of complex flow of information by extracting frequently occurring patterns fairly automatically

• built-in, broadly applied capacity that is functional at birth

• operates across sensory modalities, time and space, and species

• must be constrained, or young learners would be overwhelmed by number of statistical patterns in their surroundings

imitation

learning by copying the behaviors of others

• seen even in newborn primates, including chimps

• some investigators believe that newborns imitate as much as older children and adults do

• other argue that imitative behaviors are automatic responses to stimuli that decline with age

mirror neurons

specialized cells in motor areas of the cerebral cortex in primates that may underlie early imitation

gross mother development

control over action that help infants get around the environment

fine motor development

control over smaller movements, such as reaching and grasping

motor skills as dynamic systems

• according to dynamic systems theory of motor development, mastery of motor skills involve acquiring increasingly complex systems of action

the acquisition of each new skill is a joint product of:

• CNS development

• the body’s movement capacities

• goals the child has in mind

• child’s perceptual and cognitive capacities

• environmental supports of the skill

examples of cultural variants in infant rearing affecting motor development

• delaying sitting and walking in sandbag reared infants in China

• earlier walking among Kipsigis and West Indians

• delayed gross motor milestones in Western cultures

reaching and grasping

• prereaching: newborns poorly coordinated swipes toward objects

• at 3-4 months, purposeful forward arm movements

• at 5-6 months, reaching for objects in darkended room

• reaching is largely controlled by proprioception

ulnar grasp

clumsy motion in which fingers close against the palm

pincer grasp

well-coordinated grasp using thumb and index finger

Age ranges for reaching milestones

• newborn: prereaching

• 3-4 months: ulnar grasp

• 5-6 months: transferring object from hand to hand

• 9 months: pincer grasp

perception

active process in which we organize and interpret what we sense

speech perception

• around 5 months, infants become sensitive to syllable stress patterns in native language

• at 7-9 months, infants divide speech stream to word-like units and detect syllable stress patterns

• adults style of communicating with infants facilitates analysis of speech structure

perceptual narrowing effect

perceptual sensitivity that becomes increasingly attuned with age to information most often encountered. Evident in the perception of faces, musical rhythm, and speech sounds

visual development is supported by…

rapid maturation of the sys and visual centers in the cerebral cortex

emergence of sensitivity to depth cues

• motion at 3-4 weeks

• binocular depth cues at about 8 weeks

• pictorial depth cues beginning at 3-4 months

• independent movements promote depth perception

pattern perception

• newborns prefer patterned over plain stimuli

• with age, infants prefer increasingly complex patterns

• increasing knowledge of objects and actions supports pattern perception

size constancy

perception of an objects size as the same, despite changes in the size of its retinal image

shape constancy

perception of an objects shape as stable despite changes in shape projected on retina

intermodal stimulation

simultaneous input from more than one modality, or sensory system

intermodal perception

perception of the intermodal input as an integrated whole

amodal sensory properties

information that overlaps two or more sensory systems

differentiation theory

• infants actively search for invariant features of the environment in a constantly changing perceptual world

• later, infants notice stable relationships among features of a stimulus

affordances

action possibilities that a situation offers an organism with certain motor capabilities

cognitive point of view

the belief that babies impose meaning on what they perceive