Comprehensive Study Notes on Human Growth and Development

Theoretical Framework of Developmental Psychology

• Definition of Development: An individual change-process occurring with the passage of time as an organism moves from conception until death.

• General Features of Development:

  • Normative: Occurs for everyone within the species.

  • Non-reversible: Development is generally stable; one cannot revert to previous developmental states.

  • Reorganization: Involves a reorganization of the entire person.

  • Sequential Change: Progresses in specific stages (e.g., an infant must learn to crawl before they can walk).

Core Principles of Growth and Development

• Cephalo-caudal Principle: Development initiates from the head and progresses downward through the body. This is observed in fetal growth and continues through maturity.

  • Timeline of Structural Proportion: Progressions are noted at $2$ months, $4$ months, birth, $2$ years, $12$ years, and $25$ years as the relative size of the head decreases compared to the body.

• Proximo-distal Principle: Motor skill development begins at the center (core) of the organism and radiates outward.

  • Example: Infants first master movement of the torso, followed by the arms and legs, and finally hands and fingers.

• Orthogenetic Principle: Development proceeds from simple tasks to complex ones. Mastery of basic actions is required before complex tasks can be achieved.

• Recapitulation Theory (Heinz Werner, $1890-1964$): Developmentalists suggest that the development of an individual (Ontogenesis) can be interpreted as a recapitulation of the development of the species (Phylogenesis).

Perspectives on Development and Ageing

• Lifespan Continuum: Conception $\rightarrow$ Birth $\rightarrow$ Infancy $\rightarrow$ Toddlerhood $\rightarrow$ Pre-school age $\rightarrow$ Primary school age $\rightarrow$ Adolescence $\rightarrow$ Young adulthood $\rightarrow$ Adulthood $\rightarrow$ Old age $\rightarrow$ Death.

• Antagonistic Pleiotropy Hypothesis (George C. Williams, $1957$): Ageing is viewed as a consequence of a declining force of natural selection. Specifically, molecular mechanisms and traits that benefit young organisms may become deleterious during the later course of life, leading to aged phenotypes (e.g., the APOE-e antagonistic pleiotropy theory).

• Differentiating Growth, Maturation, and Development:

  • Development: A physical, intellectual, and emotional process.

  • Growth: Specifically refers to the physical process of development.

  • Maturation: Defined as the quality of behaving mentally and emotionally like an adult, being completely grown physically, and being well-developed/responsible.

  • Jerome Bruner's View: Suggested that the period of immaturity serves the purpose of providing time for experimental play without serious consequences.

Brain Growth and Neural Maturation

• General Progression of Brain Growth:

  • Most (but not all) neurons are present at birth.

  • Synapses and myelin develop significantly after birth.

  • Subcortical Areas: Responsible for reflexes (e.g., spinal cord, Moro reflex), these develop first.

  • Cortical Areas: Follow a specific progression, with those responsible for lower cognitive functioning developing more rapidly.

  • Last to Develop: Regions responsible for higher cognitive functioning (Prefrontal Cortex).

• Biological Rationale for Immature Development:

  • To facilitate the development of regions crucial for early survival.

  • To limit overall brain size at birth to ensure the head can pass through the birth canal.

• Maturation Stages and Timelines (Leisman et al., $2015$):

  • Neurulation: $18-24$ prenatal days.

  • Cell Migration: $6-24$ prenatal weeks.

  • Myelination: $-2$ months to $5-10$ years.

  • Synaptogenesis: $-3$ months to $15-18$ years.

  • Experience-Dependent Synapse Formation: Occurs throughout life, including neurogenesis in the hippocampus.

  • Sequence of Functionality: Seeing/hearing (visual/auditory cortex) $\rightarrow$ Receptive language/speech production (Angular gyrus/Broca's area) $\rightarrow$ Higher cognitive functions (Prefrontal cortex).

Sleep and Cognitive Development

• Lifelong Pattern: Sleep accompanies life from birth to death with significant age-dependent changes in structure.

• Sleep Stages: REM (Rapid Eye Movement), Superficial NREM (Non-Rapid Eye Movement), and Deep NREM sleep.

• Timeline of Changes: Notable shifts occur between infancy, toddlerhood, pre-school age, primary school age, pre-adolescence, adolescence, young adulthood, middle-age, and old age, reflecting brain maturation patterns.

Types of Experiences in Brain Development

• Experience-Expectant Development: Early experiences (e.g., visual stimulation, hearing, language exposure) that the developing brain requires for normal growth. This usually occurs during critical periods.

• Experience-Dependent Development: Growth and refinement of established brain structures resulting from specific learning experiences that vary based on individual and culture.

• Critical Period: A maturational stage where the nervous system is especially sensitive to environmental stimuli. If stimuli are missing, developing specific skills may be difficult or impossible.

  • Binocular Vision: $\approx 3-8$ months postnatal.

  • Emotional and Social Attachment: $0-2$ years.

  • First Language Acquisition: Birth to puberty (peak sensitivity until $\approx 7$ years).

Neural Darwinism and Brain Plasticity

• Gerald M. Edelman ($1929-2014$): Proposed the theory of neuronal group selection.

  • Principle: "Use it or lose it."

  • Pruning: Neural connections not used are pruned away.

  • Strengthening: Connections that are used develop stronger bonds.

  • Hebbian Theory: "What fires together, wires together."

  • Systemic Interaction: The organism and environment form a system; the brain enables behavior, which in turn shapes the brain.

Areas of Development (PILESS Model)

• Proposed by Tina Bruce, Carolyn Meggitt, and Julian Grenier ($2010$), development encompasses six key areas:

  • Physical development

  • Intellectual development

  • Language development

  • Emotional development

  • Social development

  • Spiritual development

Piaget’s Theory of Cognitive Development

• Jean Piaget ($1896-1880$): Viewed intelligence as something that grows through stages characterized by qualitative and quantitative differences.

• Stages of Development:

  1. Sensorimotor Stage ($0-2$ years): Knowledge is gained through movements and sensations; development of object permanence.

  2. Preoperational Stage ($2-7$ years): Symbolic thinking, use of words/pictures, pretend play. Thinking is highly egocentric. Theory of Mind begins to develop at $4$ years.

  3. Concrete Operational Stage ($7-11$ years): Logical thinking about concrete events; understanding conservation (e.g., volume of liquid remains the same in different shaped containers).

  4. Formal Operational Stage ($12+$ years): Abstract reasoning and hypothetical problem solving (logical, moral, and philosophical reasoning).

• Egocentrism: The inability to see a situation from another's point of view.

  • Three Mountains Test: Piaget found that children up to age $7$ were typically egocentric.

  • Policeman Dolls Test (Martin Hughes, $1975$): Argued the Three Mountains test was too difficult; Hughes found children could take another's perspective by age $4$.

• Animism: The belief that inanimate objects have human feelings/intentions.

  • Stage 1 (up to $4-5$ years): Almost everything is alive and has a purpose.

  • Stage 2 ($5-7$ years): Only objects that move have a purpose.

  • Stage 3 ($7-9$ years): Only objects that move spontaneously are alive.

  • Stage 4 ($9-12$ years): Only plants and animals are alive.

Theory of Mind (ToM)

• Definition: The ability to attribute mental states (beliefs, intents, desires, emotions, knowledge) to oneself and others, and understanding that others have perspectives different from one's own.

• Early Markers:

  • Protoimperative Pointing: Pointing to request things ($8-9$ months).

  • Protodeclarative Pointing: Pointing to indicate interest in an object ($8-9$ months).

• Path of Understanding:

  1. Understanding "Wanting": Others have diverse desires.

  2. Understanding "Thinking": Others have diverse beliefs.

  3. Understanding "Seeing Leads to Knowing": Knowledge access varies.

  4. Understanding "False-Beliefs": Realizing others can believe things that differ from reality.

  5. Understanding "Hidden Feelings": Realizing people can hide emotions.

• Assessment: The Sally and Anne Task (Simon Baron-Cohen, Alan M. Leslie, and Ute Frith, $1985$).

Moral Development

• Moral Realism (up to age $9-10$): Children judge "naughtiness" by the severity of the consequence rather than motives.

• Moral Relativism: Children recognize that morality depends on intentions rather than just consequences; there is no absolute right or wrong.

Theories of Social Attachment

• Imprinting (Konrad Lorenz, $1935$): Species-specific attachment to the first large moving object encountered. Suggests attachment is innate and genetically programmed.

• Human Attachment (John Bowlby, $1907-1990$): Intrinsic need for an emotional bond with the mother beyond feeding requirements.

  • Monotropy: Innate need to attach to one main figure.

  • Critical Period: Initially stated as $2.5$ years, later expanded to a sensitive period of up to $5$ years.

  • Maternal Deprivation Hypothesis: Disruption of primary caregiving leads to long-term cognitive, social, and emotional difficulties.

  • Internal Working Model: A mental representation of the world/self/others that serves as a prototype for future relationships.

• Harlow’s Monkey Experiments (Harry Harlow, $1905-1981$): Demonstrated that monkeys prefer "comfort" (cloth mother) over "food" (wire mother).

  • Impact of early deprivation can be reversed if attachment is made before the end of the critical period.

• Strange Situation (Mary Ainsworth, $1913-1999$): An assessment to identify different attachment styles characterized by parent-child interaction.

Alternative Developmental Models

• Erik Erikson’s Psychosocial Development: Extends development theory to the entire lifespan. Each stage is defined by a psychosocial conflict/task (e.g., task solved vs. task not solved), resulting in positive or negative outcomes.

Prenatal Development and Environmental Hazards

• Intrauterine Period Factors: Nutrition, protection, and exposure to Teratogens.

• Teratogens: Agents that disturb embryo/fetus development or terminate pregnancy.

• Vulnerability Timeline:

  • Weeks $1-2$: Dividing zygote; usually not susceptible to teratogens.

  • Weeks $3-8$ (Embryonic Period): High sensitivity; common sites of action include the CNS, heart, eyes, limbs, teeth, palate, and external genitalia.

  • Weeks $9-38$ (Fetal Period): Physiological defects and minor morphologic abnormalities.

• The Thalidomide Disaster:

  • $1954$: Created by Chemie Grunenthal.

  • $1956$: First affected baby born.

  • $1958$: Licensed for UK distribution.

  • $1961$: The Lancet publishes a link between the drug and birth defects.

  • Impact: Over $10,000$ children born with disabilities worldwide. Even a single $50\,mg$ capsule taken during pregnancy could cause severe defects.

Discussion and Reflection Points

• Evaluation of individuals as products of early experiences vs. ongoing change in adulthood.

• The role of developmental knowledge for Allied Health Professionals (AHP).

• The influence of education on various aspects of development.

• The nature vs. nurture debate in the context of health and professional practice.