Early Influences on Development – Nature vs. Nurture (PJ)

Life Span Development

What is the nature-nurture controversy?

Refers to disagreements about the relative roles of genetic and environmental influences on development; most developmental psychologists agree both play a role but differ in emphasis—some stress heredity and stability

What is nature?

It is defined by the hereditary factors that shape a person's identity. It is generally accepted that an individual's physical features, such as their eye and hair color, are determined by nature. Likewise, genetic diseases, such as cystic fibrosis, are known to be hereditary. However, the debate comes into play when considering personality

What is nurture?

Emphasizes environmental variables that affect behavior. Character traits can be determined by one's upbringing, relationships, culture, and community. According to social learning theory, parenting styles and learned behaviors determine a child's personality, as children learn by observation

What are the three main mechanisms of inheritance?

1. Single gene-pair inheritance

2. Sex-linked inheritance

3. Polygenic inheritance

What do heritability estimates indicate?

They indicate the extent to which variability in phenotype in a population is due to genotype differences; e.g.

What is phenotype?

Refers to observable characteristics

What is genotype?

Refers to genetic inheritance.

How does socioeconomic status (SES) impact intelligence?

Intelligence is highly heritable but influenced by SES; heritability estimates for IQ are ~.10 in low-SES children and ~.70 in high-SES children. Adoption studies confirm environmental effects.

What did the Capron and Duyme study find?

Found that adopted children’s IQs are influenced by both birth and adoptive SES—highest IQs in children born to and adopted by high-SES families

What is a critical period?

A limited time during which exposure to certain environmental factors is necessary for development to occur.

What is a sensitive period?

A longer window when it's optimal (but not necessary) for certain environmental inputs to occur; generally considered more applicable than critical periods in human development.

What is Bronfenbrenner’s ecological theory?

Describes development as involving interactions between the individual and five environmental systems: microsystem

What is the microsystem?

The child’s immediate environment—relationships with parents

What is the mesosystem?

Interactions between elements of the child’s microsystem

What is the exosystem?

External settings that influence the child’s immediate environment

What is the macrosystem?

Includes the broader social and cultural context—cultural values

What is the chronosystem?

Encompasses life-span events and transitions like parental divorce or natural disasters

What is fetal programming?

The theory that prenatal environmental exposures during sensitive periods can cause lasting changes in physiology

What is the role of the HPA axis and prenatal stress?

Prenatal stress may alter the HPA axis

When a pregnant individual experiences chronic stress, elevated maternal cortisol and CRH levels can cross the placenta, affecting fetal brain development. This can lead to:

A. Altered HPA Axis Regulation in Offspring

Hyperactivity of the HPA axis

Increased cortisol response to stress, leading to higher anxiety, depression risk, and emotional dysregulation.

Blunted HPA response. Some studies suggest prenatal stress can also lead to HPA hypoactivity, resulting in reduced stress resilience.

B. Epigenetic Changes

Prenatal stress can alter gene expression in key regulatory regions of the HPA axis, such as the glucocorticoid receptor gene (NR3C1), leading to long-term changes in cortisol regulation.

C. Neurodevelopmental and Behavioral Effects

Increased risk of anxiety, depression, ADHD, and cognitive impairments.

Altered brain structures, particularly in the amygdala (fear processing) and prefrontal cortex (emotional regulation).

What is personality?

n psychological terms, personality is a person's unique behaviors, emotions, and thought patterns

What is the heritability of personality?

Estimated at .40 to .50—suggesting both genes and environment affect personality; monozygotic twins show more similarity than dizygotic twins

What are shared environmental influences on personality?

Include factors like parenting style and SES; found to have little or no influence on personality over the lifespan.

What are non-shared environmental influences on personality?

Include different experiences with peers or siblings; these have substantial influence on personality and increase with age.

What is the heritability of intelligence?

Averages about .50 but increases with age—from .20 in infancy to .60–.80 in early/middle adulthood.

What do adoption studies show about intelligence?

Show that adopted children's IQs correlate more with biological parents over time

What is niche-picking (active genotype-environment correlation)?

Explains increasing heritability of intelligence—people seek environments matching their genetic tendencies.

How do environmental influences impact intelligence?

Shared factors have strong early influence but decline with age; non-shared factors remain low and stable across the lifespan.

What are the IQ correlations by relationship?

Identical twins reared together (.85)

What is behavioral genetics?

The study of how genetic variation influences traits like intelligence

What are twin studies?

Compare monozygotic and dizygotic twins; higher similarity in MZ twins indicates genetic influence but may be inflated due to unequal environments.

What are adoption studies?

Compare adopted children’s traits with biological and adoptive parents; stronger biological correlations suggest genetic influence—do not rely on equal environment assumption.

What are twin-adoption studies?

Combine advantages of twin and adoption studies—compare MZ twins raised together vs. apart to isolate genetic vs. environmental effects.

What is genotype-environment correlation?

Scarr’s theory describing how genetics influence the environments one is exposed to

What is passive genotype-environment correlation?

Parents provide both genes and environments that support inherited tendencies—e.g.

What is evocative genotype-environment correlation?

A child's genetic traits elicit certain responses from others that reinforce those traits—e.g.

What is active genotype-environment correlation?

Children seek environments that fit their genetic traits—e.g.

What is the developmental timing of genotype-environment correlations?

Passive and evocative correlations are strongest early in life; active correlations increase with age and autonomy.

What is reaction range?

Gottesman's concept that genes set the range of possible outcomes

What is canalization?

The idea that genetic makeup restricts development

What is Dynamic Systems Theory (DST)?

Proposes that development results from complex interactions among biology

What does DST explain about motor skills?

Thelen showed that motor behaviors like crawling emerge from interaction of physical

What is epigenetics?

The study of how environmental factors alter gene expression without changing DNA; e.g.

What are causes of epigenetic changes?

Include diet