Comprehensive Exam Study Notes on Human Development
Principles of Human Development
Core Dimensions of Human Development:
a. Movement/Physical = how our bodies function, how we move and perceive.
b. Cognitive = how we think, how we learn, how we know.
c. Language/communication = how well we comprehend and express our and others thoughts and feelings.
d. Social/Emotional = How we relate to others in families and society at large. How we feel, how we regulate our feelings.
Six Basic Tenets of Healthy Development (Halfon et al., ):
a. Development is an emergent set of developmental capacities
b. Development occurs continuously over the life span.
c. Development is a complex, non-linear process occurring in multiple dimensions, and at multiple levels and phases.
d. Development is sensitive to the timing and social structuring of environmental exposures and experience.
e. Development is an adaptive process that has been engendered by evolution with strategies to promote resilience and plasticity in the face of changing and often constraining environmental contexts.
f. Development is sensitive to the timing and synchronization of molecular, physiological, behavioral, social, and cultural function.
Conceptual Distinctions in Development:
Development as a Function of Age: Age functions merely as a chronological timeline or index variable; age itself is not the underlying causal mechanism driving psychological or physical changes, but rather a temporal structure within which biological maturation and experience unfold.
Development as Growth: Refers specifically to quantitative, additive biological and anatomical increases, such as cellular multiplication, gains in physical height, increases in body weight, and expansion of brain organ mass.
Development as Change: Represents a comprehensive framework that includes both qualitative structural reorganizations and quantitative changes across time; it accounts for functional differentiation, skill acquisition, systemic adaptations, performance shifts, dynamic regression, and organizational maintenance across the lifespan.
Developmental Milestones and Methodological Frameworks
Importance of Studying Milestones and Methods:
Establishes empirical normative baselines required to identify developmental delays, neurodevelopmental variations, and clinical pathology at early stages when plastic interventions are most successful.
Provides mechanisms to evaluate underlying theoretical frameworks concerning how biological maturation interacts with environmental experience.
Utilizes specialized, non-verbal methodologies (such as preferential looking, habituation, high-amplitude sucking, and neuroimaging) to accurately measure cognitive and perceptual competence in non-verbal infants.
Sequence and Timing of Developmental Milestones:
Age
Physical/Movement
Language/
Communication
Cognitive
Social/emotional
2 months
Holds head up when on tummy
Move both arms and both legs
Open hands briefly
Makes sounds other than crying
Reacts to loud sounds
Watches you when you move
Looks at toy for several seconds
Calms down when spoken to or picked up
Looks at your face
Seems happy to see you when you walk up to her
Smiles when you talk to or smile at her
6 months
Roles from tummy to back
Pushes up with straight arms when on tummy
Starting to try and stand
Leans on hands to support self while sitting by themselves
Takes turns making sounds with you
Blows “raspberries”
Makes squealing noises
Puts things in mouth to explore them
Reaches to grab toy they want
Closes lips to signal they don’t want to signal they don’t want food
Knows familiar people
Laughs
Likes to look at themself in a mirror
9 months
Can get to a sitting position by themself.
Moves things from one hand to another
Ability to sit without support.
Can use their hands to scrape food.
Lifts arms up to be picked up
Makes different sounds like mamama or bababa
Responds to name
Uses finger to point at things
Looks for objects when dropped out of sight
Bangs two objects together
Looks for hidden things/plays peek-a-boo
expresses differencing emotions (ex. happy, sad, angry, surprised)
recognizes name when called
is scared/clingy/shy around strangers
Smiles or laughs when you play peek-a-boo
smiles or laughs when playing games/peek-a-boo
reacts when parent leaves room
1 year
Pulls up to stand
Walks, holding onto furniture
Drinks from cup without lid as you hold it
Picks things up between thumb and pointer finger (small bits of food)
Understands no
Waves bye-bye
Calls parents “mama” or “dada”
Puts something in a container
Looks for things they see you hide
Plays games with you
2 years
Kicks a ball
Runs
Walks (not climbs) a flight of stairs with or without help
Eats with a spoon
Says at least two words together
Points to at least two body parts when you ask them to show you
Points to things in a book when you ask
Uses more gestures than just waving and pointing
Holds something in one hand while using the other hand
Tries to use switches, knobs, or buttons on a toy
Plays with more than one toy at the same time
Notices when others are hurt or upset, like pausing or looking sad when someone is? crying
Looks at your face to see how you react in a new situation
3 years
Strings items together like beads
Uses a fork
Puts on clothes by themselves, like loose pants or a jacket
Talks well enough for people to understand majority of the time
Can have a conversation with at least 2 back and forth exchange
Says first name when asked
Can draw a circle when showed how to do so
When warned, knows to avoid hot objects
Joins other children to engage in play
Notices other children and joins them to play
Developmental Plasticity Framework (Kolb) and CDC Milestones:
Kolb's Principles of Developmental Plasticity:
Structural and functional neural circuits are modified in direct response to environmental experience and intrinsic activity.
Plasticity is age-dependent; younger brains generally possess higher synaptic plasticity and compensatory capacity, though early severe insults can alter foundational developmental trajectories.
Plasticity encompasses both adaptive functional reorganization and potential maladaptive synaptic modifications resulting from toxic environmental conditions.
Interconnection with CDC Early Childhood Developmental Milestones:
CDC milestones provide behavioral indicators across social/emotional, language/communication, cognitive, and movement/physical domains at designated age intervals ( months, months, months, months, months, months, months, years, years, etc.).
The presence or absence of specific CDC milestones reflects underlying neurodevelopmental plasticity, where environmental stimulation capitalizes on open sensitive windows to consolidate functional neural pathways.
Neurobiology and Early Brain Development
Neural Structural Architecture and Functional Organization:
Neuron Architecture:
Cell Body (Soma): Contains the cell nucleus and metabolic infrastructure required for cellular survival and neurotransmitter synthesis.
Dendrites: Branching receptive structures specialized to receive chemical signals from adjacent neurons.
Axon: A long singular projection that conducts electrical action potentials away from the cell body toward target cells.
Myelin Sheath: A lipid-dense glial layer insulating the axon, facilitating rapid, saltatory signal transmission along the axon.
Synaptic Terminal Buttons: Axon terminals that store and release neurotransmitters into the synaptic cleft.
Cerebral Brain Organization:
Cerebral Cortex: Structured into two hemispheres and four primary lobes:
Occipital Lobe: Primary visual processing center.
Temporal Lobe: Primary auditory processing, language comprehension, and memory systems.
Parietal Lobe: Somatosensory processing and spatial integration.
Frontal Lobe: Motor execution, planning, working memory, attention, and executive functions.
Major Neurodevelopmental Processes:
Neurogenesis: The biological creation and proliferation of new neurons from neural progenitor cells, occurring predominantly during early prenatal development.
Synaptogenesis: The rapid formation of synaptic connections between neurons; peaks during early infancy in a period of hyper-connectivity (synaptic blooming).
Synaptic Pruning: The selective elimination of redundant, unused, or inefficient synaptic connections driven by environmental experience to maximize neural network efficiency.
Experience-Expectant Plasticity: The structural reorganization of neural circuits in response to species-typical environmental inputs that the brain evolutionarily expects to receive (e.g., standard visual patterns, basic speech sounds, spatial ambient light). Failure to receive expected inputs during strict critical windows leads to irreversible neural deficits.
Experience-Dependent Plasticity: The ongoing generation and structural refinement of neural connections based on unique, individual life experiences, formal education, and specific skill acquisition (e.g., learning to play a musical instrument or acquiring specialized domain knowledge).
Plasticity: The structural and functional adaptability of the nervous system to modify its connectivity, organization, and response patterns in response to intrinsic or extrinsic stimulation.
Critical vs. Sensitive Periods:
Critical Period: A rigid, non-negotiable temporal window during which specific environmental experience is strictly required for the normal structural development of a neural circuit (e.g., ocular dominance column formation in the visual cortex).
Sensitive Period: A flexible developmental period during which neural circuits are maximally susceptible to environmental influences, though structural adaptation can still occur to a lesser extent at later life stages.
Prematurity and Nutritional Interventions:
Prematurity Definition: A live birth occurring prior to completed weeks of gestational age.
Long-Term Effects of Prematurity: Increased incidence of executive dysfunction, motor coordination disorders, cerebral palsy, visual and auditory processing impairments, attentional deficits, learning disabilities, and altered structural brain connectivity.
Impact of Human Milk Feeding (Moniroli et al.):
Human milk provides bio-active factors, long-chain polyunsaturated fatty acids (such as docosahexaenoic acid / DHA), immunoglobulins, and neuroprotective growth factors.
Human milk feeding in preterm infants is associated with enhanced white matter microstructural integrity, accelerated cerebral cortical maturation, reduced risk of necrotizing enterocolitis (NEC), and improved neurodevelopmental performance on standardized cognitive and motor scales.
Prenatal Development and Teratology
Stages and Periods of Prenatal Development:
Germinal Period (8-10 days): Characterized by rapid cell division of the zygote, conversion into a blastocyst, and successful implantation into the endometrial lining of the uterine wall.
Embryonic Period (2-8 weeks): Period of rapid organogenesis, neural tube closure, structural morphogenesis, and cardiovascular system initialization; this stage features the highest structural vulnerability to environmental insults.
Fetal Period (Week to Birth / Weeks to ): Focuses on functional maturation of organ systems, substantial expansion of brain volume, rapid body growth, adipose accumulation, and physiological preparation for extrauterine survival.
Trimester Framework:
First Trimester (Weeks to ): Encompasses the germinal, embryonic, and early fetal periods; foundational anatomical structures form, cardiac action commences, and basic limb development occurs.
Second Trimester (Weeks to ): Characterized by rapid physical expansion, sensory structural maturation, functional fetal movement (quickening), and extensive cortical neural migration.
Third Trimester (Weeks to ): Marked by rapid brain weight increases, pulmonary surfactant production, tissue growth, and refinement of homeostatic regulation (such as temperature control).
Spatial and Developmental Trends in Utero:
Cephalocaudal Development: Growth and anatomical differentiation progress in a head-to-tail direction, where superior structures (head, eyes, brain) develop faster and earlier than inferior structures (trunk, lower extremities).
Proximodistal Development: Structural development proceeds from the central midline axis of the body outward toward the peripheral extremities (trunk and internal organs develop before distal arms, legs, hands, and feet).
Experience-Expectant Development in Prenatal Stage: Spontaneous neural firing within sensory pathways (e.g., retinal waves) and physiological cues from the maternal environment that prime neural architecture for post-natal function.
Experience-Independent Development in Prenatal Stage: Genetically determined cellular differentiation, cell migration, and structural patterning operating autonomously without requiring external sensory input.
Teratology and Environmental Exposure:
Teratogen Definition: Any external environmental agent—biological, chemical, physical, pharmacological, or maternal metabolic condition—that acts on the developing organism during prenatal development to induce structural malformations, physiological disruptions, or behavioral deficits.
Factors Influencing Teratogenicity: Dose magnitude, duration of exposure, timing relative to critical embryonic/fetal sensitive windows, genetic susceptibility of mother and fetus, and maternal metabolic status.
Case Study of Thalidomide:
Prescribed during the late s and early s as a maternal morning-sickness sedative.
Ingestion during the embryonic critical period (specifically between days and post-conception) caused severe congenital limb reduction deformities (phocomelia), ear malformations, and cardiac anomalies, demonstrating strict sensitive window timing in human organogenesis.
The Newborn Period: Reflexes, Sensory Capacities, and Diagnostic Screening
Newborn Involuntary Reflexes:
Rooting Reflex: Tactile stimulation of the newborn's cheek causes the infant to turn the head toward the stimulus and open the mouth; facilitates locate-and-latch behaviors for feeding.
Sucking Reflex: Automatic, rhythmic sucking behavior when an object stimulates the infant's hard palette; required for enteral nutrition.
Moro Reflex: Sudden loss of postural support or sudden loud noise induces arm extension, hand opening, followed by arm adduction and crying; functions as an evolutionary startle mechanism.
Palmar Grasp Reflex: Tactile pressure applied to the newborn's palm evokes involuntary, firm flexion of the fingers around the object.
Babinski Reflex: Stroking the lateral sole of the newborn's foot from heel to toe causes dorsiflexion of the hallux (big toe) and lateral fanning of the remaining toes.
Stepping Reflex: Holding the newborn upright with feet touching a flat surface induces involuntary, rhythmic alternating stepping movements.
Newborn Sensory Capabilities and Development:
Auditory System: Well-developed at birth; newborns demonstrate auditory memory, preference for human speech over non-speech sounds, preference for maternal voice, and recognition of native prosodic language structures experienced in utero.
Visual System: Least developed sense at birth; visual acuity is extremely poor (ranging from to ), fixed focal length at approximately to inches ( to ), limited color discrimination (primarily high-contrast red/white), and immature binocular convergence; undergoes rapid developmental improvement across the first months.
Somatosensory and Tactile System: Highly mature at birth; fully functional pain perception, thermal sensitivity, and responsiveness to soothing tactile pressure (skin-to-skin contact).
Olfactory and Gustatory Systems: Functional at birth; newborns distinguish sweet, sour, and bitter tastants, showing a strong preference for sweet liquids (maternal breast milk), and discriminate maternal amniotic/breast odor.
Developmental Modalities Operating in the Newborn Period:
Cephalocaudal Development: Early post-natal motor control matures from head stability downward through the trunk to lower limbs.
Proximodistal Development: Trunk control and shoulder movements emerge prior to fine motor control of digits.
Experience-Expectant Development: Visual pathway stabilization depends directly on receiving structured binocular visual input post-birth.
Experience-Independent Development: Innate brainstem-driven autonomic functions and biological reflex responses operating independently of external learning experiences.
Experience-Dependent Development: Rapid neural encoding of specific caregiver facial features, specific voice identity, and familiar localized environmental sounds.
Diagnostic Testing, Ethical Issues, and Neonatal Screening:
Purposes of Prenatal Testing: Detect chromosomal abnormalities (e.g., Trisomy ), single-gene defects, structural neural tube defects, and fetal developmental anomalies.
Limitations of Prenatal Testing: Screening assessments yield false-positive or false-negative results; invasive diagnostic options (amniocentesis, chorionic villus sampling) carry minor risks of fetal loss; test results cannot predict exact phenotypic clinical severity or long-term functional impairment.
Ethical and Clinical Issues in Infancy Testing: Questions regarding informed consent, non-directive genetic counseling, parental psychological distress, identification of actionable vs. non-actionable adult-onset genetic markers, and potential insurance discrimination.
APGAR Scale:
Purpose and Scoring: Evaluates newborn physiological condition at minute and minutes post-birth. Assesses criteria rated , , or : Appearance (color), Pulse (heart rate), Grimace (reflex irritability), Activity (muscle tone), and Respiration (respiratory effort). Total score ranges from to .
Limitations: Serves strictly as a immediate clinical tool to guide emergency resuscitation efforts; does not measure long-term cognitive outcomes, intellectual capabilities, or subtle neurological deficits.
Universal Newborn Screening Core Assessment Domains:
Metabolic Disorders: Screening for inherited enzymatic defects (e.g., Phenylketonuria / PKU, Medium-Chain Acyl-CoA Dehydrogenase Deficiency / MCADD).
Endocrine Disorders: Screening for congenital hormonal deficiencies (e.g., Congenital Hypothyroidism, Congenital Adrenal Hyperplasia).
Functional Hearing and Structural Cardiac Screening: Objective assessments including Otoacoustic Emissions (OAE) / Auditory Brainstem Response (ABR) for congenital hearing loss, and pulse oximetry screening for Critical Congenital Heart Disease (CCHD).
Perception, Motor Development, and Cognitive Systems
Paradigm Shifts in Motor and Cognitive Theories:
Preformationism / Experience-Independent Stance: Historical view postulating that developmental outcomes are driven entirely by pre-programmed genetic blueprints, treating environmental experience as irrelevant.
Behavioral Theory / Experience-Dependent Stance: Early reductionist view positing that motor and cognitive behaviors are shaped almost exclusively through external environment conditioning, passive learning, and external reinforcement.
Dynamic Systems Theory / Experience-Expectant Stance: Modern, unified framework viewing motor control and cognitive skills as emergent, self-organizing processes arising from real-time interactions among biological maturation, physical body dynamics, task goals, and environmental contexts.
Esther Thelen's Research on Motor Development:
Investigated the unexpected disappearance of the newborn stepping reflex around to months of age.
Experimental Manipulations:
Submerged infants' legs in warm water: Stepping reflex reappeared due to fluid buoyancy counteracting leg mass.
Added physical weights to infants' legs during active stepping: Stepping reflex ceased.
Theoretical Significance: Proved that reflex disappearance was not caused by cortical neuroanatomical maturation inhibiting subcortical centers, but rather by changes in physical body composition (rapid leg mass accumulation outpacing muscle strength growth). Demonstrates that motor changes are emergent outcomes of dynamic multi-system interaction.
Key Terminology of Dynamic Systems Theory:
Open System: A non-isolated, complex system that continuously exchanges energy, matter, and information across its boundaries with the surrounding environment.
Phase Shift: A sudden, qualitative reorganization of a system's global behavioral pattern when a continuous underlying variable crosses a critical threshold.
Emergence: The spontaneous self-organization of novel, complex behavioral patterns arising from interactions among simpler subsystems without an explicit internal or central blueprint.
Attractor State: A preferred, stable, energy-efficient behavioral pattern or trajectory that a dynamic system tends to occupy.
Control Parameter: An underlying variable whose continuous change induces a system-wide instability, eventually forcing a phase shift into a new structural state (e.g., leg strength acting as a control parameter for independent walking).
Research Methodologies, Neuroscience, and Computational AI Modeling:
Novelty Preference Paradigm: Operates on infants' innate bias to look longer at novel stimuli compared to familiarized stimuli; used to assess visual processing speed, discrimination, and memory encoding.
Electroencephalography (EEG): Non-invasive scalp recording measuring event-related electrical potential changes in cortical neural populations with high temporal precision.
Magnetic Resonance Imaging (MRI) / Functional MRI (fMRI): Imaging modalities offering high spatial resolution; MRI captures structural neuroanatomy, whereas fMRI tracks hemodynamic blood-oxygen-level dependent (BOLD) signals indicating localized neural activity.
Functional Near-Infrared Spectroscopy (fNIRS): Non-invasive optical technique monitoring localized cortical hemoglobin oxygenation changes; highly tolerant to infant head motion compared to fMRI.
Computational Approaches and AI Modeling: Utilizing Google deep learning architectures and Generative AI to construct structural models of infant visual categorization, self-supervised representation learning, and motor skill emergence.
Quinn's Categorization Research (Cat/Dog Paradigm):
Findings: Infants familiarized with continuous series of cat visual stimuli demonstrate significant novelty preference when subsequently presented with a dog stimulus (and vice versa).
Categorical vs. Conceptual Development: Demonstrates that infants construct perceptual categories early in life based on shared visual features (e.g., head shape, facial proportions) before acquiring formal semantic/conceptual domain knowledge.
Infant vs. Adult Category Processing: Like adults, infants utilize categorical representations to simplify complex environmental inputs; unlike adults, early infant categories are highly bound to immediate perceptual input and lack dense semantic networks.
Ayzenberg () Object Recognition Framework:
Mechanisms of Object Recognition (Table ): Outlines core computational properties including holistic visual processing, structural edge/skeletal extraction, volumetric object coding, and viewpoint-invariant visual recognition.
Acuity and Object Recognition Development (Figure ): Illustrates how low initial visual acuity in early infancy acts as a functional filter, forcing the visual system to prioritize broad spatial frequencies and global structural shape prior to fine detail processing.
Conceptual Integration: Connects early perceptual visual constraints directly to functional cognitive development, showing how natural physiological limitations optimize subsequent category and object discovery.
Language Acquisition, Processing, and Developmental Speech-Language Disorders
Basic Linguistic Distinctions:
Language: A complex, rule-governed, arbitrary symbolic system used to represent and communicate thoughts, ideas, and abstract concepts across modalities (spoken, signed, written).
Speech: The peripheral motor execution and oral-acoustic production of articulate vocal sounds that express spoken language.
Voicing: The physiological production of raw sound through vocal fold vibration within the laryngeal assembly.
Dialect: A systematic, rule-governed regional, ethnic, or social variation of a primary language encompassing distinct phonological, lexical, and syntactic structures.
Dimensions of Language and Differential Developmental Rates:
a. Phonology = units of sounds (“lee” sound, “v”, “ing” sound)
b. Morphology = units of meaning (“leave” means go away/depart “ing” means something is happening)
c. Semantics = meaning of words (“leaving” is an act of departing)
d. Pragmatics = use and intent (my goal is to leave)
e. Syntax = rules of the language (“I am leaving this town”)
f. Prosody = rhythm stress, intonation to convey emotion/meaning (do you really mean it this time?)
g. Nonverbal Communication = facial, body gestures (frown, smile)
Prerequisites for Speech Processing in Newborns (Kujala, ):
a. Phoneme discrimination and identification
b. Sound discrimination
c. Binding together sound features
d. Detecting invariant features from variable sound
e. Detecting and learning wordforms
f. Grouping sounds and temporal patterns
g. Extracting wordforms from speech by statistical learning
h. Timing and prosodic cues in wordform learning
i. Tracking phrases and sentences
j. Tracking speech by sequence structure
k. Tracking speech by prosody
l. Tracking speech by auditory stream segregation
Expressive vs. Receptive Language Dimensions:
Expressive Language: The capacity to construct, produce, and execute communicative linguistic output through spoken words, gestures, signs, or written text.
Receptive Language: The capacity to process, decode, comprehend, and interpret incoming linguistic input. Receptive language capabilities systematically precede and exceed expressive language skills across typical development.
Vocalization Milestones and Word Emergence:
Cooing / Early Vocalization Stage: Emerges at 4 to months; consists of vowel-like sounds, gurgling, and pleasure vocalizations.
Canonical / Reduplicated Babbling: Emerges at 7to 8 months; involves repetitive consonant-vowel (CV) syllabic chains (e.g., "ba-ba-ba", "da-da-da").
Variegated / Non-Reduplicated Babbling: Emerges at to months; features varied consonant and vowel combinations within single utterances (e.g., "ba-da-bu").
Jargon Vocalization Stage: Emerges at to months; characterized by variegated babbling overlaid with adult-like intonation contours, stress patterns, and communicative intent.
First Words Emergence: Occurs between and months (average at months); marks the transition into true symbolic language production.
Vocabulary Expansion and Telegraphic Speech:
Vocabulary Spurt (Naming Explosion): A period of accelerated word production typically occurring between and months, initiated after an expressive milestone of approximately words.
Developmental Word Count Metrics: Expressive vocabulary reaches approximately to words by age ; receptive vocabulary expands dramatically to between and words by age 6$.\n * Telegraphic Speech: Two-word utterances emerging around 18 to 24 months; contains high-content semantic words (nouns, verbs, adjectives) while completely omitting non-essential function words, prepositions, and grammatical morphemes (e.g., "more milk", "daddy go"), while adhering strictly to native language word order rules.\n* Methodological Tools in Infant Cognitive Research:\n * Violation of Expectation (VOE) Method: Measures visual looking duration to quantify infants' surprise or disconfirmation of expectations when presented with physically or logically impossible events versus possible events.\n * Distinction from Novelty Preference: Novelty preference measures passive visual preference for unfamiliar visual stimuli based on perceptual habituation memory; VOE measures cognitive expectation violations and implicit domain knowledge disconfirmation.\n* Key Empirical Studies in Language Acquisition:\n * Werker Perceptual Narrowing Study: Demonstrated that young infants ( to months) function as "citizens of the world," capable of discriminating phonemic contrasts across all human languages; by to months, perceptual narrowing occurs, restricting phonemic discrimination specifically to the contrasts present in the infant's native language environment.\n * Johnson and Newport Critical Period Study: Examined native Korean and Chinese immigrants arriving in the United States between ages and ; established a strong negative linear correlation between age of arrival and ultimate grammatical proficiency up until puberty, after which performance plateaued with extreme individual variance, demonstrating age-dependent sensitive period constraints on native syntax acquisition.
Language Disability and Speech-Language Clinical Distinctions:
Language Disability Definition: A significant structural impairment in the comprehension, production, or functional utilization of spoken, written, or symbolic language systems, affecting semantics, syntax, morphology, or pragmatics.
Expressive Speech Delay vs. Expressive Language Delay:
Expressive Speech Delay: A localized motor-articulatory disorder impairing oral motor planning, speech sound clarity, and acoustic sound execution; affects phonology and speech mechanics, while underlying cognitive-linguistic capacity, vocabulary structure, and syntactic understanding remain fully intact.
Expressive Language Delay: A cognitive-linguistic structural deficit impairing word retrieval, sentence construction, morphological markers, and expressive vocabulary accumulation; syntax, semantics, and morphology are heavily impaired, while motor articulation and physical speech output mechanisms may function normally.