Chapter 5 - Physical Development In Infants And Toddlers

25 July 2022
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Cephalocaudal Principle
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Growing from the top and extending downward Head develops first Toddlers have disproportionately large head and trunk
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Features of human growth
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Indicators are height and weight Boys achieve half their adult height by 2 years, girls by 18 months
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Muscle fibers
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Are present at birth Muscles become longer and thicker through childhood as the individual fibres fuse together Process accelerates in adolescence
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Fat
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Layer of fat appears under the skin near the end of the fetal period It accumulates rapidly during the first year after birth, which we call baby fat Children become leaner during preschool but acquire more fat during early elementary years Occurs more rapidly during adolescence, especially in girls
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Children at risk for obesity show signs around the ages of...
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4 to 6 years
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Bone
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Begins to form during prenatal development Embryonic period: middle of cartilage (flexible tissue) turns to bone Fetal period: ends of cartilage structures (epiphyses) turns to bone The structure is then hard at each end and in the middle Working from the middle, cartilage turns to bone until the enlarging middle section reaches the epiphyses, ending skeletal growth
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Secular growth trends
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Changes in physical development from one generation to the next that are related to environmental factors Today, adults and children are taller and heavier than people of previous generations
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Average does not always mean normal
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The normal range for developmental milestones is much larger then what is considered "typical"
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3 Mechanisms of Physical Growth
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1) Heredity 2) Hormones 3) Nutrition
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Mechanisms of Physical Growth - Heredity
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Correlation for height between identical twins is larger than fraternal twins Moderate correlation between the average height of the two parents' heights and the child Heredity plays a role in determining height and the rate at which it is achieved
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Mechanisms of Physical Growth - Hormones
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Chemicals that are released by glands and travel in the bloodstream to act on other areas of the body Pituitary gland (in the brain) secretes growth hormone Thyroid gland (in the neck) secretes thyroxin
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Growth hormone (GH)
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Secreted during sleep, sometimes after exercise GH travels to the liver and triggers the release of somatomedin Not even GH can lead to dwarfism
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Somatomedin
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Causes muscles and bones to grow Triggered by GH
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Thyroxin
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Needed for nerve cell development and basic cell functioning Cognitive delay results without enough Can make the pituitary gland ineffective and therefore retarding physical growth Too much is linked to anxiety problems
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Mechanisms of Physical Growth - Nutrition
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40% of energy is devoted to growth in a 2 month old and they need to consume many calories to support it Best to introduce food one at a time in order to isolate allergies or sensitivities Breast feeding is good By 2 years, children need less to eat and they often become picky eaters which is a part of independent growth (they are unsure what is safe to eat)
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Breast feeding benefits
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Contains maternal protective antibodies Babies can develop allergies to formula In developing nations, risk of contaminated water when bottle feeding
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Challenges to healthy growth in children
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1) Malnutrition 2) Diseases 3) Accidents
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Malnutrition
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A lack of adequate nutrition indicated, in part, by children being small for their age Especially damaging during infancy because growth is so rapid during this time Malnourished children are often listless and inactive in order to conserve energy Parents need to be shown how to foster development A combination of food availability, nutrition education and behavioural change is necessary to prevent malnutrition
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Diseases
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More than half of the 5.9 million deaths of children under the age of 5 could be prevented by basic, affordable interventions Certain disorders are increasing in prevalence for children Asthma in children under 15 has increased 9% Education of parents on the importance of vaccines is very important 5 conditions that account for the majority of childhood deaths: pneumonia, diarrhea, measles, malaria and malnutrition
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Accidents
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While infant mortality is usually related more to birth defects and low birth weight, after the first year of life children are more likely to die from accidents than any other single cause Motor vehicle accidents are the most common cause of accidental death usually because they aren't restrained properly Also die often from burns or suffocation when they aren't supervised properly
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Neuron
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Basic unit of the brain and nervous system Specializes in receiving and transmitting information
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Cell body
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At the centre of the neuron and contains the basic biological machinery that keeps the neuron alive
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Dendrite
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Branch-like extensions off the neuron that allow for intercellular communication
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Axon
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Tube-shaped structure attached to the cell body that transmits electrical messages received through dendrites to other neurons
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Myelin
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The fatty sheath that insulates the axon and speeds up information transfer
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Terminal buttons
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Small knob structures at the end of the axon that release neurotransmitters
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Neurotransmitters
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Chemicals that carry information to nearby neurons They affect the firing of surrounding neurons
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Synapse
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The gap between one neuron and the next
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Cerebral cortex
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The wrinkled surface of the brain Made up of about 10 billion neurons Regulates many of the functions we think of as being distinctly human Consists of two halves
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Cerebral hemispheres
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The right and left halves of the cerebral cortex
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Corpus callosum
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Millions of axons in a thick bundle that link the right and left hemispheres of the cerebral cortex
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Frontal cortex
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An area at the front of the brain that is responsible for your ability to make and carry out plans and for your personality For most, the ability to produce and understand language, to reason, and to compute is due to the neurons in the left hemisphere Artistic and musical abilities, perception of spatial relationships, and ability to recognize faces and emotions comes from neurons in the right hemisphere
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Emerging brain structures
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Beginning of brain development occurs in zygotic period At 3 weeks after conception, neural plate forms At 4 weeks, neural plate folds to form the neural tube which later becomes the brain and spinal cord When the ends of the tube fuse shut, neurons are produced in one small region of the neural tube At 10 weeks, production of neurons begins At 28 weeks, the developing brain has all of the neurons it will ever have Neurons form at the rate of 4000 per second From the neuron manufacturing site in the neural tube, neurons migrate to their final positions in the brain The brain is built in stages, starting with the innermost layers Neurons in the innermost layers are positioned first then moving outward Layering process continues until all 6 layers are in place At 4th month, axons acquire myelin and this process continues into adolescence Neurons that carry sensory information are the first to acquire myelin and the neurons in the cortex are the last In the months after birth, the brain grows rapidly: the axons and dendrites grow longer, the dendrites sprout new limbs, and the number of synapses and dendrites increases After baby's first birthday, synapses disappear gradually
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Neural plate
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A group of cells forming about 3 weeks after conception that develops into the neural tube, brain and spinal cord
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Synaptic pruning
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A period in infancy and later in adolescence during which synapses begin to disappear as the brain weeds out unnecessary or under-utilized connections between neurons
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Electroencephalogram (EEG)
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Measurement of electrical activity A pattern of brain waves If a region of the brain regulates the function, the region should show distinctive EEG patterns during that function
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Functional magnetic resonance imaging (fMRI)
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measures the flow of blood in the brain using magnetic fields
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Positron emission tomography (PET Scan)
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traces glucose uptake in the brain
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Functional near infrared spectroscopy (fNRIS)
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Measures blood flow in the brain and is less invasive than fMRI and easier to use on infants Silent method
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Frontal cortex - more detailed
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Begins to function early, seen in 5 day old babies Regulates primarily deliberate, goal-oriented behaviour Regulates feelings and emotional experience Left hemisphere regulates language processing Right hemisphere regulates recognizing non-speech sounds, emotions and faces Regulating emotion and intentional behaviours is a function of the frontal cortex
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Neuroplasticity
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the extent to which brain organization is flexible Some believe the organization of brain function is predetermined genetically Others believe experience helps determine the functional organization of the brain If children sustain brain injuries, they may have a developmental problem such as impaired language skills but the brain's plasticity allows them to recover the function as other neurons take over the processing The brains organization and function can be affected by experience but its development follows some general biochemical instructions so most people end up with similar brain organization
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Motor skills
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coordinated movements of the muscles and the limbs e.g. crawling must be done in a specific way and in the right sequence
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Locomotion
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to move around in the world
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Fine-motor skills
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activities, such as grasping, holding, and manipulating objects, that involve small-muscle groups opposable thumbs allow us to do this
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Gross-motor skills
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activities, such as running, throwing, and jumping, that require large-muscle groups requires the coordination of the large muscle groups
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Reflexes
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unlearned responses that are triggered by a specific form of stimulation e.g. rooting and sucking reflexes help them get the life sustaining nutrients they need e.g. blinking and withdrawal reflexes help them avoid unpleasant stimulation
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Babinski reflex
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a baby's toes fan out when the sole of the foot is stroked from heel to toe significance: unknown
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Blink reflex
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a baby's eyes close in response to bright light or a loud noise significance: to protect eyes
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Moro reflex
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a baby throws its arms out and then inward (as if embracing) in response to a loud noise or when its head falls significance: may help a baby cling to its mother
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Palmar reflex
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a baby grasps an object placed in the palm of its hand significance: precursor to voluntary walking
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rooting reflex
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when a baby's cheek is stroked, it turns its head toward the stroking and opens its mouth significance: helps a baby find the nipple
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stepping reflex
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a baby who is held upright and is moved forward begins to step rhythmically significance: precursor to voluntary walking
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sucking reflex
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a baby sucks an object when it is placed in its mouth significance: permits feeding
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withdrawal reflex
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a baby withdraws its foot when the sole is pricked with a pin significance: protects a baby from unpleasant stimulation
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Locomotion progress
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4 months: sit upright with support 7 months: sit upright without support 9 months: stand if holding on to an object for support 14 months: stand alone and walk with assistance 15 months: walk alone 24 months: climb steps, walk backward, kick ball
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Dynamic systems theory
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new perspective that upholds that motor development involves many distinct skills, organized and reorganized over time to meet the demands of specific tasks ex) walking requires maintaining balance, moving limbs, perceiving the environment and having a reason to move
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Posture and balance
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Babies and toddlers are top heavy requires visual system, inner-ear mechanisms and large-muscle group activation once they can stand they must continuously adjust their posture to keep them from falling down by a few months old, they use visual cues and inner-ear mechanism
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Stepping
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have to be able to stand in order to step happens around 10 months old variety of techniques to encourage stepping
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Perceptual factors
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use perceptual factors to determine if a surface is ok to walk on if unsuitable they will resort to crawling on slopped surfaces they will resort to a slide or scoot backwards
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Coordinating skills
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mastering skills requires the coordination of many individual skills Requires differentiation and integration need to know when to integrate certain behaviours and when to inhibit them
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Differentiation
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mastery of component skills
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Integration
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combining component skills in a sequential order
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Beyond walking
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running comes fast after walking key goal is to launch body in the air and maintain balance when landing
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Reaching and grasping
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4 months: can reach for objects; but not a smooth process - short, disjointed movements 5 - 6 months: coordinate different motions in each hand 7 - 8 months: use thumbs to grasp objects 12 months vs 24 months: differences in spoon use as a result of changing wrist movements - in this year there is a big change in their ability to use their wrists
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Handedness
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young children use left and right hands interchangeably by kindergarten, handedness is well established and difficult to reverse heredity and experience play a role - modern cultures favour right handedness
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Maturation, experience and motor skill
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Progress in large muscle or fine-motor skills is due to a combination of genetics and experience Improvement from experience is limited to specific muscle groups
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Senses
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Sense organ translates the physical stimulation into nerve impulses that are sent to the brain
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Smell
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Newborns have a keen sense of smell Respond positively to pleasant smells and negatively to unpleasant smells Can recognize familiar odours
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Taste
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Newborns have a highly developed sense of taste Can differentiate between tastes Have a sweet tooth Can detect changes in the mother's breast milk
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Touch
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Respond reflexively to touch
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Pain
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tricky to measure, very subjective their nervous system can transmit pain they respond in stereotypical ways to pain-provoking stimuli chronic pain can cause intense stress which can impact development facial expressions and heart rate are good indicators
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Hearing
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Fetus can hear at 7-8 months gestation can get startled, blinks and movements are good indicators infants don't hear as well as adults can hear sounds in human range; i.e. not to high or low pitched by 4.5 months they can recognize their own name can differentiate vowels and consonant sounds at 30 months they have full auditory capacity
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Auditory threshold
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the quietest sound that a person can hear infants is lower than adults
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Auditory (sound) localization
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ability to detect where a sound is coming from they can detect general location and distance of sound
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Seeing
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infants look at patterned stimuli more than non-patterned stimuli they have an immature and inefficient optical system for detecting color
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Visual acuity
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the smallest pattern that can be dependently distinguished
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Color detection
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they detect wavelength (color) with neurons called cones in the retina by 3 - 4 months color perception capabilities is similar to adults
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Cones
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specialized neurons in the retina of the eye
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size constancies
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the realization that an objects actual size remains the same despite changes in the size of retinal image at 4-5 months they realize objects do not constantly change size as they move closer or farther away
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shape constancy
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when a door opens, the shape changes but we know it is still the same size
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perceptual constancies
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brightness and color are other peceptual constancies they are achieved in rudimentary form by 4 months
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Depth
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objects have 3 dimensions: 1) height 2) width 3) depth we use perceptual processing to infer depth - retinal disparity - texture gradient - relative size - interposition
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Visual cliff
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apparatus used to determine if infants can infer depth glass-covered platform infants can detect a difference between the shallow and deep sides of a cliff, but adults fear it
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retinal disparity
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left/right eyes see different versions of the same scene a cue used to infer depth for distant objects, images are at a similar position on the retina for near objects, images appear in different positions
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texture gradient
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cue for depth perception arising from an object's surface texture near objects: finer details distant objects: coarser details
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relative size
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cue for depth perception based on an object's size distant objects: are smaller near objects: are larger
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interposition
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cue for depth perception based on the degree to which an object is blocked from view by another object distant objects: partially obstructed near objects: in full view
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edges
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lines that mark the boundaries of objects important for defining objects help to distinguish stationary objects; elements that move together are part of the same object infants use edges and motion to distinguish objects
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two anatomically separate visual systems
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1) determining perception of objects 2) interpreting visual information from objects that are moving
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the face in seeing
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general principles of perception explain how infants perceive faces faces have stimuli that move (eyes/mouth) faces have contrast (eyes, lips, teeth)
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integrating sensory information
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soon after birth, infants coordinate info from different senses infants recognize by sight and object that they have felt previously infant learn to integrate what they see with what they hear - e.g. nursing mother provides visual and taste cues to her baby adults faces have adult voices, children faces have child voices