Nature: The role of Heredity
Heredity (nature) provides the genetic blueprint for traits such as intelligence, personality, and physical characteristics. In other words, Genes are like instructions written in DNA. Depending on how those instructions combine, traits show up differently.
Some traits are polygenic, while others are due to a single pair of genes.
Polygenic
* Meaning: Traits influenced by many genes working together, not just one.
* Example: Height, intelligence, and skin color.
* Flashcard Tip: “Poly = many → many genes shape complex traits.”
Dominant Gene
* Meaning: A gene that shows its effect even if only one copy is present.
* Example: Brown eyes—if you inherit one brown-eye gene, you’ll likely have brown eyes.
* Flashcard Tip: “Dominant = takes charge.”
Recessive Gene
* Meaning: A gene that only shows its effect if you inherit two copies (one from each parent).
* Example: Blue eyes—you need two blue-eye genes to have blue eyes.
* Flashcard Tip: “Recessive = needs backup.”
Homozygous
* Meaning: Having two of the same gene version (alleles).
* Example: Two blue-eye genes = homozygous for blue eyes.
* Flashcard Tip: “Homo = same.”
Heterozygous
* Meaning: Having two different gene versions (alleles).
* Example: One brown-eye gene + one blue-eye gene = heterozygous. Brown shows because it’s dominant.
* Flashcard Tip: “Hetero = different.”
Heritability Estimate
a concept in behavioral genetics that quantifies how much of the variation in a trait within a population can be attributed to genetic differences (the extent to which phenotypes vary within groups due to differences in genotype), as opposed to environmental factors.
📊 Key Points
* Population-based, not individual-based:
* A heritability estimate of 0.60 for intelligence means that 60% of the variation in IQ scores in that population is linked to genetic differences.
* It does not mean that 60% of an individual’s intelligence is genetic.
* Context-dependent:
* Heritability estimates change depending on the population studied and the environment.
* Example: Height has a high heritability (~80%), but poor nutrition can lower average height outcomes.rved traits.
Bronfenbrenner’s Ecological Model
Mneumonic: “My Messy Ex Makes Chaos”
Conceptualizes human development as shaped by nested environmental systems that interact over time.
These systems illustrate how various environmental contexts influence human development.
What are Rutter’s Indicators of Risk?
These factors increase vulnerability to psychopathology.
Adverse Childhood Experiences (ACEs)
Adverse Childhood Experiences (ACEs) are potentially traumatic events that occur before age 18—such as abuse, neglect, or household dysfunction—that can have long-lasting effects on physical health, mental health, and life opportunities.
Abuse
* Physical (being hit or harmed by an adult)
* Emotional (being insulted, humiliated, or threatened)
* Sexual (inappropriate sexual contact or exploitation)
Neglect
* Physical (not having food, clothing, or safe shelter)
* Emotional (lack of protection, support, or consistent care)
Household Challenges
* Parental separation or divorce
* Domestic violence (intimate partner violence in the home)
* Substance misuse in the household
* Mental illness in the household (e.g., depression, suicide attempts)
* Incarcerated household member
Werner’s Kauai Longitudinal Study
High-risk infants can show resilience if they experience fewer stressors and have supportive relationships.
Landmark research project on resilience, following all 698 children born in 1955 on the Hawaiian island of Kauai from birth into adulthood. It revealed that despite exposure to poverty, perinatal complications, and family adversity, about one-third of high-risk children grew into competent, caring, and successful adults.
📊 Key Findings
* Risk factors: About 30% of the cohort grew up in poverty, with additional stressors like parental psychopathology, divorce, or chronic family conflict.
* Negative outcomes: Two-thirds of children exposed to four or more risk factors by age two developed learning or behavioral problems by age 10, or delinquency/mental health issues by age 18.
* Resilience: Remarkably, one-third of high-risk children did not develop significant problems. They became competent, confident, and caring adults, succeeding in school, maintaining healthy relationships, and setting realistic life goals.
Reaction Range
Genetic makeup sets boundaries for potential development, but environment determines where within that range an individual actually falls.
The reaction range refers to the range of possible phenotypic outcomes for a given genotype, depending on environmental influences.
In other words, genes provide limits, but environment shapes expression.
🧬 Example
* Intelligence (IQ):
* A child may have a genetic potential IQ range of 90–120.
* If raised in a stimulating, supportive environment, they may reach the higher end (closer to 120).
* If raised in a deprived environment, they may fall toward the lower end (closer to 90).
* Height:
* Genes may set a potential height range (e.g., 5’6”–6’0”).
* Adequate nutrition and health care allow the child to reach the upper limit, while malnutrition may keep them at the lower limit.
What is Canalization?
A narrow developmental path that traits take, showing resistance to environmental forces.
Highly canalized traits are less influenced by the environment.
Three (3) types of genotype-environment correlation.
Passive Genotype–Environment Correlation
Occurs when children inherit both their genes and the environment shaped by their parents.
Evocative Genotype–Environment Correlation
Happens when an individual’s genetic traits elicit specific responses from others in their environment.
Active Genotype–Environment Correlation
Individuals actively seek out or create environments that align with their genetic predispositions.
These correlations describe how genetics and environment interact to shape individual attributes.
What is Epigenesis?
It emphasizes bidirectional influences between genes and environment, showing that genes do not act in isolation.
Epigenesis suggests that experiences can shape gene expression.
What is Ethology?
The study of animal and human behavior in natural environments, focusing on biological instincts.
Ethology emphasizes the role of evolution in shaping behavior.
What is a Critical Period?
A narrow window during which specific experiences are essential for normal development.
Missing experiences during a critical period can lead to permanent impairment.
What is a Sensitive Period?
A broader window when the brain is receptive to certain experiences, allowing for development later with more effort.
Sensitive periods are more flexible than critical periods.
What are the stages of Prenatal Development?
Each stage has distinct developmental milestones and vulnerabilities.
What causes birth defects?
Chromosomal disorders, exposure to teratogens, and poor maternal health.
Birth defects can result from genetic and environmental factors.
What is an example of a Dominant Gene Disorder?
Huntington’s Disease.
This disorder results from the inheritance of a single dominant gene.
What is an example of a Recessive Gene Disorder?
Cystic Fibrosis.
This condition requires two copies of a recessive gene to manifest.
What are common teratogens?
Teratogens can interfere with normal prenatal development, leading to various abnormalities.
What is Fetal Alcohol Syndrome (FAS)?
The most severe form of Fetal Alcohol Spectrum Disorder (FASD) characterized by a triad of physical, cognitive, and behavioral abnormalities.
FAS results from significant prenatal alcohol exposure.
What are the diagnostic features of Fetal Alcohol Syndrome (FAS)?
These features are used to diagnose FAS in children.
What is Fetal Alcohol Syndrome (FAS)?
A condition diagnosed with distinct facial features after confirmed maternal alcohol use during pregnancy.
What are the common deficits associated with Alcohol-Related Neurodevelopmental Disorder (ARND)?
Give an example of a child diagnosed with ARND.
A 9-year-old with confirmed prenatal alcohol exposure shows poor working memory and social immaturity but lacks facial anomalies.
What does Alcohol-Related Birth Defects (ARBD) refer to?
Physical malformations without CNS involvement.