Human Development: PSYC101 - Fall 2025

Development: Defined as the comprehensive pattern of continuity and change in human capabilities that unfolds throughout a person's entire lifespan, encompassing both periods of growth and instances of decline.

Nature: Refers to a person's biological endowment, encompassing all genetic and inherited factors.
Nurture: Encompasses a person's environmental and social experiences, including family, peers, culture, socioeconomic status, and learning opportunities.
Both nature and nurture are critical and inextricably linked contributors to development.
Emergent Property: An individual is an emergent property, representing a complex consequence resulting from the dynamic interaction of numerous lower-level biological, psychological, and social factors.
Genotype: This term refers to an individual's complete genetic heritage, representing the 'nature' component.
Phenotype: These are the observable characteristics of an individual, which visibly manifest the contributions and interplay of both nature (genotype) and nurture (environmental experiences).

Development is influenced by a continuous interplay of experiences; both early life experiences and those encountered later in life make significant and ongoing contributions to a person's trajectory.
Resilience: This is a crucial human capability defined as a person's inherent capacity to effectively recover from or successfully adapt to challenging, stressful, or difficult times. Research indicates that resilient children are more likely to develop into competent and capable adults.

Germinal Period ( $weeks ext{ } 1 ext{ } and ext{ } 2$ ):
- Begins with conception.
- Characterized by rapid cell division and the eventual attachment of the zygote (fertilized egg) to the uterine wall.
Embryonic Period ( $weeks ext{ } 3 ext{ } to ext{ } 8$ ):
- A period of intensive cell differentiation, where cells begin to take on specialized functions.
- Crucial for the formation of organs and basic body structures.
Fetal Period ( $months ext{ } 2 ext{ } to ext{ } 9$ ):
- Marked by a significant increase in the functioning and maturation of organs.
- Characterized by substantial increases in fetal weight and size.

Teratogen: Any agent or factor that can cause a birth defect or negatively alter prenatal development. Examples include:
- Substances like nicotine, alcohol, and various illegal or prescription drugs.
- Certain illnesses or maternal infections.
The specific effects of a teratogen are highly dependent on the timing and duration of exposure during prenatal development; different organ systems are vulnerable at different stages.
Fetal Alcohol Spectrum Disorders (FASD): A range of physical, cognitive, and behavioral abnormalities caused by maternal alcohol consumption during pregnancy.
The environment a child experiences after birth can significantly influence and potentially mitigate the long-term effects of prenatal teratogen exposure.
Preterm infants (born before $37$ weeks of gestation) and low birth-weight infants (weighing less than $5.5$ pounds) face an elevated risk for various developmental difficulties, including physical, cognitive, and socioemotional challenges.

Within $12$ months: Infants typically develop gross motor skills such as sitting upright independently, standing, stooping, climbing, and frequently begin walking.
In the second year: Children demonstrate rapid and significant gains in more complex motor skills, including running and climbing with greater proficiency.
An important reciprocal relationship exists between motor skills and perceptual skills; they depend on and influence each other's development.
Environmental experiences, such as opportunities for exploration and practice, play a crucial role in the refinement and development of these skills.
Preferential Looking: A widely used research technique where an infant is presented with a choice of two or more objects or images and researchers measure which object the infant looks at for a longer duration. This method helps infer an infant's visual preferences and cognitive abilities.
Infant Preferences: Shortly after birth, infants show a natural preference for looking at faces, suggesting an innate social predisposition.

Myelination: The process by which nerve fibers are insulated with a myelin sheath continues extensively after birth, enhancing the speed and efficiency of neural communication.
Synaptic Connections: The number of neural connections (synapses) in the brain increases dramatically during infancy and early childhood, forming complex networks.
Synaptic Pruning: Unused or weaker synaptic connections are systematically eliminated or