Early Physical Development

Mr. Koch

AP Psychology

Andover High School

Prenatal Development�(these stages of prenatal development are out of the scope of the CED but provided for background and context)

• Conception
• A single sperm fertilizes a single ovum (egg) to create a zygote
• “germinal stage” - process of rapid cell division and then differentiation
• At about 10 days, attaches to wall of uterus
• Outer cells form placenta, inner cells develop into embryo

Prenatal Development �(these stages of prenatal development are out of the scope of the CED but provided for background and context)

• Embryonic Stage
• Stage from 2-9 wks after conception
• Organs begin to form and function
• Develops heart, nervous system, stomach, esophagus, ovaries or testes
• Develop eyes, ears, nose, jaw, mouth lips
• By end have tiny arms w/ elbows, hands, fingers
• Legs have knees, ankles, toes

Prenatal Development�(these stages of prenatal development are out of the scope of the CED but provided for background and context)

• Fetal Stage
• 7 month period of prenatal development, spanning 9 weeks from conception to birth
• Begins to look distinctly human
• Organs grow and start to function
• By 3 months: can kick, make fist, turn head, open mouth, swallow, frown
• In 6^th month: eyelids open, has tastebuds, well-developed grasp, can breathe regularly as long as 24 hrs. at a time
• Could potentially survive premature birth by end of 6^th month
• Organ systems typically functional by end of 7^th month
• 8^th & 9^th month: respond to light & touch, hear outside sounds
• Can also learn – respond differently to sound of mother (faster heartbeat) and stranger (slower heartbeat)

Teratogens

• Potentially harmful agents (i.e. viruses, chemicals) that can affect prenatal development
• Placenta screens out most harmful substances, but these sneak through
• Especially harmful if during embryonic stage
• “critical period” in prenatal development
• If heart, eyes, ears, hands, feet don’t appear, cannot form later – if formed incorrectly, defects are permanent
• Teratogens during fetal stage affect size, behavior, intelligence, and health

Teratogens

• Disease
• Can be born with HIV or experience physical defects from other diseases like rubella
• Drugs (both legal and illegal)
• Can experience withdrawal symptoms after birth
• can lead to premature birth, underweight, tense, fussy, delayed physical growth & motor development, behavior & learning problems
• Note: concern over supposed “crack baby” epidemic in the 80s and 90s never materialized in long term
• Smoking/nicotine
• Can cause respiratory problems, irritability, social/attention problems, greater risk for nicotine addiction later in life, can harm brain development
• Can cause reduction of nutrients that can lead to premature and underweight birth, which can cause cognitive and behavioral problems

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Teratogens

• Alcohol
• Can kill fetal brain cells – depresses fetal nervous system, putting at risk for birth defects & mental retardation
• Fetal Alcohol Syndrome (FAS)
• Characterized by mental retardation, possible physical malformations
• Behavioral and psychological problems also linked to genetic mutations, maternal illness (flu), stress, depression, etc. in first 6 months
• Fortunately, vast majority of infants (>90% in western nations) are born without mental or physical problems

Newborns

• How do we study capabilities of infants?
• Very difficult – present stimuli & monitor response
• Eye movements, changes in heart rates, sucking rates, brain waves, body movements, and skin conductance
• Habituation = decrease in responding with repeated stimulation

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• Can see at birth
• Blurry, but able to see large, close objects
• Seem to prefer faces and seem prepared to distinguish from other visual stimuli
• Born with limited hearing capabilities
• Notice single note differences of tone, turn head toward sounds, particularly attuned to sounds of speech
• Similar sense of smell & taste to adults, but less developed
• Breast-fed infants show preference for smell of own mother to others
• In general, infants’ sensory abilities seem to dispose to focus attention on caregiver

Newborn Reflexes

• Born with numerous reflexes that aid survival
• Involuntary, unlearned motor behaviors
• Ex. “rooting” reflex, sucking, etc.
• Most disappear in 3-4 months when brain development allows voluntary control of muscles and development of motor skills

Brain Development

• Born with overabundance of neurons, but immature (connections poorly developed)
• After birth, neural networks develop rapidly until puberty when “pruning” process gains importance

Maturation

• Brain development helps

enable maturation

• Natural growth or change that

unfolds in a fixed sequence,

relatively independent of

environment

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• Must be biologically prepared for certain changes to develop
• Fine and Gross Motor Coordination enables skills that lead to independence
• Age of maturation will vary, but sequence rarely does
• However, research shows that once properly matured, experience can impact efficiency, effectiveness of development
• Once again, nature and nurture interact