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Physical Development in Infancy and Toddlerhood (Comprehensive Study Notes)

Learning Goals

  • Goal 1: Body Growth

  • Goal 2: Brain Development and Learning Capacities

  • Goal 3: Motor Development

  • Goal 4: Perceptual Development

Body Growth

  • Infants grow rapidly over the first 2 years; weight gains are matched by increases in length. Growth is not uniform across all body parts. There are gender and ethnic differences in infant weight and length.

  • Decreasing proportions in the neonate: At birth, the head represents rac{1}{4} of the neonate’s body. By adulthood, the head is rac{1}{8} the size of the body. This is due to differential growth rates across body parts.

  • Growth pattern in infancy: faster growth than at any other time, occurring in spurts. Key data:

    • Newborn: height = 20\text{ inches} , weight = 7.5\text{ pounds}

    • End of year 1: height = 32\text{ inches}, weight = 22\text{ pounds} (growth cited as 50\%\text{ greater than birth height} in some summaries; height increases from 20 to 32 inches = 12\text{ inches}, a 60\% increase).\n - End of year 2: height = 36\text{ inches}, weight = 30\text{ pounds} (height increase from birth: 16\text{ inches}; weight quadruples from birth to 30 pounds).

  • Individual and group differences:

    • Growth norms: average height and weight by age

    • Gender and ethnic differences are apparent

    • Individual variation due to nutrition and other factors

    • Skeletal age is the best estimate of physical maturity

Nutrition and Breastfeeding

  • Breastfeeding is crucial for development in the first two years and has multiple benefits:

    • Ensures nutritional completeness

    • Provides correct fat–protein balance

    • Helps ensure healthy physical growth

    • Protects against disease

    • Protects against faulty jaw and tooth development

    • Ensures digestibility

    • Smooths transition to solid foods

  • Ethical/practical note: Mothers in the developing world are often unaware of the benefits of breastfeeding and may rely on low-grade commercial formula and ingredients.

Preventing Overweight in Children

  • Recommendations to reduce overweight risk:

    • Breastfeed exclusively for the first six months

    • Avoid foods high in sugar, salt, and saturated fats

      • Children under 2 years old should NOT be given candy/gor processed sugars and should instead be encouraged to eat whole foods such as fruits, vegetables, and whole grains.

    • Provide opportunities for energetic play; limit TV viewing

    • Babies wake up a lot more when breastfed compared to being given formula because they digest breast milk more quickly, leading to more frequent feedings.

Brain Development and Learning Capacities

  • The Nervous System and Brain: The Foundations of Development

  • Environmental influences on brain development:

    • Plasticity: the degree to which a developing structure (e.g., the brain) or behavior is modifiable due to experience

      • Neuroplasticity

    • Sensitive period (0-2 years old): a specific but limited time, usually early in life, during which the organism is particularly susceptible to environmental influences relating to some development facet

      • Genes provide basic foundation of cognitive structure but enviroment and experience can either enhance or inhibit the expression of these genetic potentials, shaping individual developmental outcomes.

Sleep Patterns

  • Sleep patterns: infancy sleep–wake cycles gradually shift toward a night–day schedule; total sleep time declines over time

  • Factors influencing sleep changes:

    • Brain development

    • Cultural beliefs and practices

    • Parents’ needs and schedules

    • Increased melatonin secretion

    • Attachment to caregiver

SIDS (Sudden Infant Death Syndrome)

  • Definition: the sudden and unexplained death of an infant between 1 month and 1 year old that remains unexplained after investigation; exact cause unknown, though risk factors exist and ways to reduce risk are known

  • Prevalence: about 2,300 babies in the United States die of SIDS each year

Classical Conditioning

  • Classical Conditioning: Pairing a neutral stimulus with a stimulus that prompts a reflexive response

  • Purpose: helps infants recognize which events typically occur together

  • Result: the environment becomes more orderly and predictable

Operant Conditioning

  • Operant Conditioning: the infant acts on the environment (operant)

  • Key components:

    • Reinforcer: increases the occurrence of a response

    • Positive reinforcement: presents desirable stimulus

    • Negative reinforcement: removes an unpleasant stimulus

    • Punishment: decreases the occurrence of a response

    • Positive punishment: presents an unpleasant stimulus

    • Negative punishment: removes a desirable stimulus

Reinforcement and Punishment (Summary)

  • Reinforcement (increases desirable behavior):

    • Positive reinforcement: adds a stimulus

    • Negative reinforcement: removes a stimulus

  • Punishment (decreases undesirable behavior):

    • Positive punishment: adds a stimulus

    • Negative punishment: removes a stimulus

Motor Development

  • Motor development involves both gross-motor and fine-motor skills; new achievements build on previous ones

  • Gross-motor development: crawling, standing, walking

  • Fine-motor development: reaching, grasping

  • The rate of motor progress varies widely

Gross- and Fine-Motor Development in the First Two Years (Milestones)

  • Graspes cube: 3 months, 3 weeks

  • Sits up alone: 7 months

  • Crawls: 7 months

  • Pulls to stand: 8 months

  • Plays pat-a-cake: 9\text{ months}, 3\text{ weeks}

  • Walks alone: 11\text{ months}, 3\text{ weeks}

  • Scribbles vigorously: 14\text{ months}

  • Jumps in place: 23\text{ months}, 2\text{ weeks}

Perceptual Development

Milestones of Reaching and Grasping

  • Newborn: prereaching

  • 3–4 months: ulnar grasp

  • 4–5 months: transferring object from hand to hand

  • 9 months: pincer grasp

Developments in Hearing

  • 4–7 months: sense of musical phrasing

  • 6–7 months: distinguishes musical tunes based on variations in rhythmic patterns

  • 6–8 months: screens out sounds not used in native languages

  • 6–12 months: detects sound regularities in human speech

  • 7–9 months: begins to divide speech stream into wordlike units

Visual Development

  • Supported by rapid maturation of eyes and visual centers in the brain

  • Milestones:

    • 2 months: focus

    • 4 months: color vision

    • 6 months: acuity, scanning, and tracking

    • 6–7 months: depth perception

The Development of the Senses

Smell and Taste; Sensitivity to Pain and Touch

  • Infants are born with the capacity to experience pain

  • Touch is one of the most highly developed sensory systems in a newborn and one of the first to develop

  • Infants are born with a developed sense of smell and can distinguish mom’s smell if breastfeeding

  • Infants have an innate preference for sweetness

Visual Perception

  • Newborns can see up to about 20\text{ inches} away

  • By 6 months , many infants have 20/20 vision

Auditory Perception

  • Infants hear before birth and have good auditory perception after birth

  • They can differentiate their mother’s voice from other voices