Genetic basis: extra copy of chromosome 21 (Trisomy 21)
Causes are not fully clear
Prenatal Development
Prenatal development lasts about 9 months (~266 days) and unfolds in three stages:
Germinal (zygote) stage
Embryonic stage
Fetal stage
The Germinal Stage
First 2 weeks after fertilization
Zygote attaches to uterine wall; basic structures form:
Amniotic sac: protects the fetus
Umbilical cord: supplies blood
Placenta: endocrine organ that supplies hormones
The Embryonic Stage
Weeks 3 to 8
Formation of vital organs
By 8 weeks, distinct features appear
The embryonic stage is highly vulnerable to environmental influences
The Embryonic Stage and Teratogens
Teratogens: substances that cause disorders or defects in a developing embryo or fetus
Any chemical that alters normal development
The Fetal Stage
Week 9 to birth
By the end of month 4: fingernails, eyebrows, eyelashes, external body parts, movement
Ongoing refinement of organs, features, and body systems through birth
Physical Development: Birth through Childhood
Development of the Brain
We have nearly all the neurons we will ever have at birth
Brain is about 25% of adult weight at birth
Major question: what changes occur from birth to adulthood?
Early development shows rapid increases in brain size due to neural connections
By 6 months: brain ~50% of adult size; by 2 years ~75%; by 5 years ~95%
Early brain development follows an orderly sequence: primary motor cortex, then sensory cortices (visual and hearing), then refinement of sensory and motor abilities
Environmental Impacts on Brain Development
Developing brain is highly neuroplastic
Early environmental enrichment enhances brain development
Lab animals in enriched environments develop larger brains due to increased neuron size and greater axon/dendrite complexity
Physical Growth
First 6 months: infants double birth weight
First year: triple birth weight; grow ~50% taller
Growth slows around age 3; about 2-3 inches per year until adolescence
Motor Development
Newborn reflexes serve protective and nutritive functions
Key reflexes and expected durations:
Rooting: head turns, mouth opens; drops out around 9 months
Moro (startle): arm extension; drops out around 3 months
Darwinian (grasping): strong fist; drops out around 2 months
Swimming: coordinated swimming in water; drops out around 6 months
Tonic neck: head turning; drops out around 6 months
Babinski: toes fan; drops out around 6-9 months
Walking: stepping motions; drops out around 2 months
Placing: foot against edge of surface; drops out around 1 month
Motor Development: Progression to Complex Skills
From 14-18 months: walking and climbing (cerebellum development)
From 30-35 months: bladder and bowel control (potty training)
Cognitive Development
What is Cognitive Development?
Questions about remembering, perspective-taking, logical reasoning, and symbol use
Piaget’s Theory of Cognitive Development
Jean Piaget emphasized age-related changes in thinking
Key processes:
Assimilation: interpreting new information using existing schemas
Accommodation: restructuring knowledge to fit new information better
Four Stages of Cognitive Development
Sensorimotor (Birth to ~2 years)
Preoperational (~2 to 7 years)
Concrete Operational (~7 to 12 years)
Formal Operational (12+ years)
The Sensorimotor Stage: Birth to ~2 Years
Learning about the world via sensory experiences
Object permanence develops gradually: objects continue to exist when out of sight
Early numerical understanding and imitation of others
Operational momentum concept: tendency to overestimate the outcomes of addition and underestimate subtraction
The Preoperational Stage: ~2 - 7 Years
Children begin using symbols and language
Emergent imagination and pretend play; language development accelerates
Concepts remain immature; “pre-concepts” present
Key features:
Centration: focusing on one perceptual factor at a time
Conservation: changing form does not change essential properties
Egocentrism: self-centered viewpoint; limited Theory of Mind
Theory of Mind still developing
Key Features of the Preoperational Stage
Carnet of cognitive biases and limitations as described above
The Concrete Operational Stage: ~7 - 12 Years
Logical operations emerge
Mastery of conservation and decentration; ability to evaluate multiple dimensions
Better classification, ordering, and categorization
Thinking remains concrete; struggles with hypothetical or abstract problems
The Formal Operations Stage: 12+ Years
Abstract, hypothetical, and deductive reasoning emerges
Systematic hypothesis testing and complex problem solving
Abilities become more sophisticated into adulthood
Psychosocial Development
Attachment
Attachment is the emotional bond between an infant and caregiver
Developmental sequence:
Indiscriminate attachment (0-6/7 months): social behaviors toward everyone
Specific attachment: increased responsiveness to primary caregivers
Separate attachments: by 12-18 months, interest expands to others beyond the primary caregiver
Measuring Attachment: The Strange Situation
Mary Ainsworth (1979) developed the Strange Situation Task
Procedure:
Child plays with toys in a new room
Mother and a stranger present initially
Mother leaves the room
Mother returns
Observation of infant's reactions to caregiver absence and reunion
Parenting Styles and Development
Three main styles:
Permissive: hands-off, few rules, limited punishment, low structure
Authoritarian: strict rules, high expectations, punitive, limited discussion
Authoritative: balanced approach with clear rules, but also solicits child input and encourages independence
Cultural Differences in Parenting
Effects of parenting styles depend on context and culture
Cultural emphases on family/collective values vs. individual independence affect outcomes
Socioeconomic status and environment also influence parenting and child outcomes
Erikson’s Theory of Psychosocial Development
Eight-stage theory spanning the lifespan
Stages and core tensions (brief):
Trust vs. Mistrust (infancy)
Autonomy vs. Shame and Doubt (toddlerhood)
Initiative vs. Guilt (early childhood)
Industry vs. Inferiority (elementary years)
Identity vs. Role Confusion (adolescence)
Intimacy vs. Isolation (early adulthood)
Generativity vs. Stagnation (middle adulthood)
Ego Integrity vs. Despair (older adulthood)
Erikson’s Eight Stages (Overview)
Infancy (birth to 18 months): Trust vs. Mistrust
Toddler (18 months to 3 years): Autonomy vs. Shame/Doubt
Preschool (3 to 6 years): Initiative vs. Guilt
Elementary (6 to 12 years): Industry vs. Inferiority
Adolescence (12 to 18 years): Identity vs. Role Confusion
Early Adulthood (20 to 40 years): Intimacy vs. Isolation
Middle Adulthood (40 to 60 years): Generativity vs. Stagnation
Older Adulthood (60+ years): Ego Integrity vs. Despair
Erikson’s Summary Table (Table 8-4)
Infancy: Trust vs. Mistrust — if needs are met and caregiver is consistent, child develops trust
Toddler: Autonomy vs. Shame/Doubt — encourage independence to foster autonomy; overprotection leads to doubt
Preschool: Initiative vs. Guilt — encourage questions and exploration; discouragement leads to guilt
Elementary: Industry vs. Inferiority — tasks should be challenging but achievable; fosters competence
Adolescence: Identity vs. Role Confusion — develop stable sense of self and roles; avoid confusion
Early Adulthood: Intimacy vs. Isolation — form meaningful relationships; avoid isolation
Middle Adulthood: Generativity vs. Stagnation — contribute to others’ well-being and achieve goals
Older Adulthood: Ego Integrity vs. Despair — reflect on life with a sense of purpose or experience despair
Language Development
Language Development: What is Language?
Language is a system of symbols and rules for communication
Global language variety: ~7,000 spoken languages and ~300 writing systems
Language is uniquely human; while other animals communicate, human language is more abstract and symbolic
Psycholinguistics
Study of how humans translate sounds and symbols into meaning
Five levels of rules studied:
Phonemes
Morphemes
Syntax
Semantics
Pragmatics
How is Language Acquired?
Theoretical perspectives:
Learning (Behaviorism & Social Learning): Skinner & Bandura
Genetic (Innateness): Chomsky
Interactionist (Learning + Genetics): combination of both
Four Stages of Language Acquisition
Early vocalizations: cooing (4-6 weeks) to babbling (6 months)
By 9-12 months, babbling approaches phonemic inventory
First words around 1 year: 1-12 words; words carry broad meanings (e.g., “up” = “pick me up”)
Condensed speech: ~1-2 years; sentences begin to form
Semantic Relations in First Sentences (Common Patterns)
Matrix of relations showing simple sentence structures and meanings, e.g.:
They name an actor and an action: "Daddy eat"
They modify a noun: "Bad doggy"
They indicate possession: "Mommy shoe"
They describe location: "Dog outside"
They describe an action and a location: "Go home"
They name an action and an object: "Eat lunch"
They describe an actor and an object: "Mommy lunch"
Source material excerpt adapted from Gleason et al. (1998)
Four Stages of Language Acquisition (Continued)
Expanded Language (after ~age 2): rapid vocabulary growth; several hundred words every 6 months
Syntax develops with ongoing rule development; some overgeneralization and simplification occur (e.g., "Deers", "I slept in bed" → "I sleeped in bed")
Language and vocabulary continue to refine through adulthood
Language in the Brain
Two major brain areas:
Broca’s Area (Frontal Lobe): language production; damage leads to Broca’s Aphasia (fluent speech difficulty)
Wernicke’s Area (Temporal Lobe): language comprehension; damage leads to Wernicke’s Aphasia (word-finding and comprehension difficulties)
Example resources: video demonstrations of aphasia (links provided in course materials)
Adolescence: Physical Development
Physical Development in Adolescence
Puberty: rapid physical changes including height/weight growth and secondary sex characteristics
Triggered by hypothalamus signaling the pituitary to release gonadotropins, leading to estrogen/testosterone production
Brain Development in Adolescence
White matter (myelinated axons) continues to grow into the mid-20s
Prefrontal cortex maturation improves control over the midbrain reward system
Reward processing differs in adolescents; limbic system and hippocampus continue maturational changes
Cognitive Development in Adolescence
Continued progression through Piaget’s Formal Operations Stage
Kohlberg’s Theory of Moral Development describes changes in moral reasoning with age
Stages include:
Preconventional Morality (Ages ~3-7): self-interested reasoning based on rewards/punishments
Conventional Morality (Ages ~8-13): conforming to social rules and expectations
Postconventional Morality (about ~25% of adults): universal ethical principles and social contracts
Alzheimer’s disease is the most common form of senile dementia
Successful Aging
Despite decline, life satisfaction and happiness can peak in old age
Two key practices to age well:
Regular exercise slows cognitive and physical decline
Strong social support reduces mortality and cardiovascular risk
Summary of Key Concepts and Connections
Development debates (nature vs. nurture, continuity vs. stages, critical periods) inform interpretation of all subsequent topics
Prenatal and early postnatal experiences set trajectories for brain development and attachment patterns
Genetics and environment interact to shape phenotypes; twin studies help disentangle their contributions
Language and cognitive development progress through well-defined stages with characteristic capabilities and limitations
Adolescence features continued brain maturation, shifts in moral reasoning (Kohlberg), and evolving identity formation (Erikson)
Across the lifespan, psychosocial bonds (attachment, parenting style, identity, intimacy, generativity) influence well-being and adjustment
Aging encompasses physical and cognitive shifts but can be offset by activity, social engagement, and supportive networks
Connections to Foundational Principles
Nature vs. nurture underpins genetic and epigenetic mechanisms; environmental inputs influence brain development and behavior
Piaget’s stages illustrate how cognition becomes more abstract and less concrete over time, guided by assimilation and accommodation
Erikson’s theory emphasizes lifelong psychosocial development with stage-specific crises and resolutions
Kohlberg’s stages describe evolving moral reasoning anchored in social norms and universal ethical principles
Language development integrates genetics, neurology (Broca’s/Wernicke’s areas), and social input (child-directed speech, semantics, pragmatics)
Practical and Ethical Implications
Early intervention and enriched environments can promote better developmental outcomes
Cultural variation in parenting practices calls for culturally sensitive expectations and supports
Understanding critical periods highlights the importance of timely educational and social experiences
Ethical considerations in studying infants (e.g., Strange Situation) require safeguarding child welfare and informed consent from caregivers
Aging and dementia raise societal considerations for healthcare, caregiver support, and social inclusion
Key Formulas and Notable Numbers (LaTeX)
Brain growth milestones:
By 6 months: brain is approximately 0.50 of adult size
By 2 years: approximately 0.75 of adult size
By 5 years: approximately 0.95 of adult size
The prenatal timeline is approximately 9 months (≈ 266 days)
Developmental stage age ranges (summarized):
Sensorimotor: birth to ~2 years
Preoperational: ~2 to 7 years
Concrete Operational: ~7 to 12 years
Formal Operational: 12+ years
Kohlberg’s levels and stages denote progression through moral reasoning from obedience/punishment to universal ethical principles (stages 1–6, grouped into Level One, Level Two, Level Three)
Cross-Reference to Course Materials and Videos (Notes for Further Review)
Strange Situation task by Mary Ainsworth (1979) for attachment assessment
Harlow’s monkey experiments (1950s) on contact comfort
Discovering Psychology videos on child development and language (language development, development milestones)
Eye-tracking research for infant cognition (non-invasive measurement of attention and expectation
Quick Reference: Key Definitions
Attachment: emotional bond between infant and caregiver
Teratogen: substance causing developmental disorders or defects
Chromosome disorders: Down syndrome = Trisomy 21
Epigenetics: regulation of gene expression not caused by changes in DNA sequence
Neuroplasticity: brain’s capacity to reorganize and adapt in response to experience
Conservatism in cognition: understanding that quantity remains the same despite changes in form (conservation)
Theory of Mind: understanding that others have thoughts and perspectives different from one's own
Socioeconomic and cultural factors: essential moderating influences on development and parenting outcomes