5.1: Reading ASSIGNMENT                                        

5.1: Reading ASSIGNMENT                                         Date 2/9/25

Conception 

• Conception:  When a sperm fertilizes an egg, to create a new life. Human reproduction is both natural and wondrous.
  
  

• Egg (Ovum):

  • Released by a woman’s ovary.

  • A woman is born with all the immature eggs she will ever have.

  • Only 1 in 5000 will mature and be released.

• Sperm:

  • A man begins producing sperm at puberty.

  • Sperm production continues 24/7 throughout life but slows with age.

  • More than 1000 sperm are produced per second.

• Fertilization Process:

  • About 200 million sperm are deposited in the reproductive tract.

  • They race upstream toward an egg 85,000 times their size.

  • Sperm releases digestive enzymes to break through the egg’s protective layer.

  • Once one sperm penetrates, the egg blocks all others.

  • Within half a day, the egg and sperm fuse, creating a single cell.

• The Probability of Existence:

  • Out of millions of sperm, only one wins.

  • Your existence is the result of a long chain of successful conceptions

  • If any event had changed, you might not have existed.

Prenatal Development 

Stages of Development

• Zygote (conception to 2 weeks)
  
  

  • Fewer than half survive beyond 2 weeks.

  • Rapid cell division occurs, forming about 100 identical cells in the first week.

  • Cells begin to differentiate (specialize in structure and function).

  • Around 10 days after conception, zygote attaches to the uterine wall.

  • Inner cells become the embryo; outer cells become the placenta (transfers nutrients & oxygen).

• Embryo (2 to 9 weeks)

  • Organs form and begin functioning.

  • Heart starts beating within the first 6 weeks.

  • In 1 in 270 cases, zygote splits into two, forming identical twins.

• Fetus (9 weeks to birth)
  
  

  • Looks human by 9 weeks.

  • By the sixth month, organs like the stomach develop enough for survival if born prematurely.

  •  The fetus can hear the mother’s voice in the womb and respond  - 

  • After birth, newborns prefer their mother’s voice & language.

  • If the mother spoke two languages, the newborn showed interest in both.

  • Newborns cry in the intonation of their mother’s native language (e.g., French = rising tone, German = falling tone).

Fetal Learning & Memory

• Fetuses can learn before birth

•  Around 2 months before birth, they adapt to repeated sounds (e.g., a honking device placed on the mother’s belly).

•   Memory: After 4 weeks, they recognize and react less to familiar sounds.

Teratogens & Risks

• The placenta filters harmful substances but some, called teratogens( e.g., viruses, drugs), can cause harm.

• Alcohol use during pregnancy:

  • Alcohol use during pregnancy is dangerous!

  • Alcohol affects both mother and baby’s central nervous system.

  • Can make the baby more likely to like alcohol later in life.

  • Experiments  with rats showed babies preferred alcohol if the mother drank while pregnant.

  • Even small amounts of alcohol can harm the baby (binge drinking or occasional drinking).

  • Heavy drinking → birth defects, behavior problems, hyperactivity, lower intelligence.

  • Fetal Alcohol Syndrome (FAS):

    • 1 in 800 infants affected.

    • Causes lifelong physical & mental abnormalities.

    • Can cause small head size & abnormal facial features

    • Epigenetic effect: Alcohol modifies DNA, turning genes on/off abnormally. Alcohol during pregnancy messes up the instructions, causing parts of the baby’s brain or body to develop incorrectly.

 The Competent Newborn

• Babies are born with built-in reflexes to help them survive.

• Withdrawal Reflex → Moves limbs away from pain.

• Breathing Reflex → If something blocks their breathing (like a cloth), they turn their head and swipe at it.

• Feeding Reflexes:

  • Rooting Reflex → When touched on the cheek, babies turn their head toward the touch and search for a nipple.

  • Sucking Reflex → Once they find a nipple, they automatically start sucking, which requires coordinated tonguing, swallowing, and breathing.

  • Crying → Babies cry when hungry; this motivates parents to feed them.

How Do Researchers Study Infants' Abilities?

• William James thought newborns experienced a "blooming, buzzing confusion."

• 1960s research proved babies can communicate through:

  • Gazing (looking at things)

  • Sucking (on pacifiers)

  • Turning their heads

Habituation (Getting Used to Things)

• Definition: Babies stop responding to things they see or hear repeatedly.

• Example: A baby will react to a new sound but stop noticing it after hearing it many times.

• Used to study what infants notice and remember.

What Do Newborns Prefer to Look At?

• Face Recognition Study:

  • Babies prefer to look at faces rather than other objects.

  • When shown mixed-up cat-dog pictures, babies focused on the face of the new animal.

• Face Preference:

  • Newborns turn toward human voices.

  • Prefer objects 8-12 inches away (which is the distance from a baby to their mother’s face when nursing).

Sense of Smell & Memory

• Babies recognize their mother’s scent within days of birth.

• Study:

  • 1-week-old babies turned toward a gauze pad that smelled like their mother’s bra.

  • Long-Term Memory of Scents:

    • Mothers who used chamomile-scented nipple cream → Babies preferred chamomile-scented toys 21 months later.

    • Suggests early scent memories last for a long time.

Brain Development

• Maturation:

  • Maturation is the sequence of biological growth that allows changes in behavior, largely uninfluenced by experience.

  • Growth is genetically driven, similar to how a flower grows according to its genetic instructions.

  • Early milestones include standing before walking and using nouns before adjectives.

  • Severe deprivation or abuse can delay development.

  • Both genetic growth (nature) and experiences (nurture) interact in development.

Brain Development:

• Prenatal Development:
  
  

  • The brain grows very fast before birth, creating about 250,000 new nerve cells every minute. 

  • It makes more neurons than needed, reaching the highest number at 28 weeks of pregnancy, then adjusting to around 23 billion at birth.

• Infancy and Childhood:

  • A baby is born with almost all the brain cells it will ever have, but the brain is not fully developed yet. 

  • After birth, the connections between brain cells grow quickly, helping the baby learn to walk, talk, and remember things.

• Age 3-6 Development:

  • The frontal lobes grow quickly between ages 3 to 6, helping preschoolers learn to focus, make decisions, and control their actions better.

• Association Areas:

  • Areas linked to thinking, memory, and language are the last to develop.

  • As these areas develop, mental abilities increase, leading to improved cognitive function.

• Neural Pruning:

  • A pruning process removes unused neural links (connections the synapses)and strengthens those that are used. This process helps the brain become more efficient.

Motor Development

• Physical Coordination: Developing the brain allows infants to gain physical skills as muscles and the nervous system mature.

• Universal Sequence:

  • Babies roll over before sitting unsupported.

  • They crawl on all fours before walking.

  • This sequence is not learned by imitation, but due to brain maturation (blind children follow the same pattern).

• Timing Differences:

  • 25% of babies walk by 11 months, 50% by their first birthday, and 90% by 15 months 

  • In the U.S., infant stomach sleeping dropped from 70% to 11%, and SIDS deaths halved after the 1994 campaign

Genes & Maturation:

• Genes Guide Development: Identical twins often walk on the same day 

• Rapid cerebellum development at age 1 helps prepare infants for walking.

  • Early experiences have little effect on physical skills, like walking, bowel, and bladder control.

• Toilet Training: Toilet training won’t be successful if a baby’s muscles and brain aren’t developed enough. No amount of begging or punishment will help until the baby’s body is ready to control their bathroom habits.

Brain Maturation and Infant Memory

• Infantile Amnesia: Early memories rarely form before age 3. Example: Preschoolers who were 4–5 years old during a fire evacuation could recall the alarm and its cause 7 years later, while 3-year-olds could not.
  
  

• Earliest Conscious Memory: Studies show the average age for earliest memory is about 3.5 years. As children grow (ages 4–8), memory recall improves, allowing them to remember experiences for longer.
  
  

• Brain Development: The parts of the brain that help with memory, like the hippocampus and frontal lobes, keep developing until the teenage years, which helps improve memory.

• Rovee-Collier’s Experiment (1965):
  
  

  • Infants can learn and remember simple actions.

  • Experiment: A mobile (a crib toy with hanging parts) was tied to a baby’s foot. The baby learned to kick to move the mobile.

  • Results: Babies remembered this association even a month later but did not recognize a different mobile.

• Childhood Language Memories:
  
  

  • Even if people forget a language spoken as a child, their nervous system retains traces of it.

  • Study: British adults who had no conscious memory of Hindi or Zulu could relearn sound contrasts from those languages even at age 40.

Summary: Conception occurs when a sperm fertilizes an egg, beginning prenatal development, which progresses through the zygote, embryo, and fetus stages. Babies start learning in the womb, recognize sounds, and are influenced by teratogens like alcohol, which can cause Fetal Alcohol Syndrome. At birth, infants have automatic reflexes for survival, and their brain and motor skills develop in a universal sequence, with genetic maturation guiding milestones like walking. While early experiences shape cognitive growth, motor development is largely driven by biology, and even forgotten childhood languages can leave lasting traces in the brain.