Behavioral Genetics – Personality and Individual Differences

Vocabulary flashcards summarizing major terms, researchers, and findings from the lecture on behavioral genetics, intelligence, and personality.

Behavioral Genetics

Field that studies how genes and environmental factors jointly influence behavior and individual differences.

Francis Galton

Pioneer who first speculated about genetic and environmental contributions to intelligence.

Twin Studies

Research design comparing identical (MZ) and fraternal (DZ) twins to estimate genetic versus environmental variance in traits.

Monozygotic Twins (MZ)

Identical twins who share 100 % of their genetic material.

Dizygotic Twins (DZ)

Fraternal twins who share roughly 50 % of their segregating genes.

Heritability Estimate (HE)

Statistic indicating the proportion of trait variance within a population attributable to genetic differences.

Heritability of IQ

Typically ranges from .50 to .70, meaning genetics explain about 50–70 % of IQ variance.

DNA (Deoxyribonucleic Acid)

Molecule made of nucleotides (deoxyribose, phosphate, nitrogenous bases) that carries genetic instructions.

Nucleotide

Basic building block of DNA, consisting of deoxyribose, phosphoric acid, and an organic base.

Genome

The complete set of chromosomes and genes inherited from one’s parents.

Genotype

An individual’s complete genetic makeup encoded in DNA.

Phenotype

The observable expression of genes in physical and behavioral traits.

General Intelligence (g)

Overall cognitive ability; about half of its variance is due to genetic differences.

Plomin & Spinath (2004)

Found IQ similarity rises with genetic relatedness and shared upbringing has modest effects.

Assortative Mating

Non-random partnering with individuals who share similar genetic traits, such as high IQ.

Spousal IQ Correlation

Around r = .40, higher than correlations for many physical or personality traits.

Socioeconomic Status (SES)

Environmental factor—such as income and education—that influences intellectual development.

Longitudinal Twin Findings

MZ IQ correlations remain stable or rise with age, whereas DZ correlations decline after adolescence.

Adoption Study Result

Adopted children’s IQs resemble biological parents more than adoptive parents, underscoring genetic influence.

McGue et al. (1993)

Showed adopted siblings’ IQ similarity decreases with age, indicating growing genetic impact.

Multivariate Genetic Analysis

Method assessing whether two traits share common genetic influences beyond their individual heritabilities.

Zuckerman (1991)

Concluded that most personality dimensions have substantial heritable components; non-shared environment is less important than genes.

Gigantic Three

Broad personality factors—Extraversion, Neuroticism, Psychoticism—shown to be largely inherited.

Extraversion

Trait linked to happiness, self-confidence, and higher potential for substance use.

Neuroticism

Emotional instability; heritability estimates typically range from .30 to .50.

Loehlin (1992)

Reported heritabilities of .30–.50 for Extraversion and Neuroticism, tied to physiological arousability.

Molecular Genetics

Research area mapping behavioral traits to specific genes.

Lesch et al. (1996)

Identified a gene variant associated with trait anxiety (Neuroticism).

Allele

One of two or more alternative forms of a gene occupying the same locus on homologous chromosomes.

Sensation-Seeking Allele Length

Longer alleles are linked to higher sensation-seeking tendencies.

Reward Deficiency Hypothesis

Theory that genetic dopamine deficits lead individuals to seek substances for relief and pleasure (Blum et al., 2000).

Heritability of Substance Abuse

HE ranges from .40 to .60 for alcohol, stimulants, cannabis, indicating polygenic influences.

Psychoticism

Personality dimension associated with impulsivity and higher risk of substance abuse; typically higher in men.

Gene–Environment Correlation

Concept that genetic makeup can influence the environments one selects or creates.

Multiplicative Model

Framework stating that genetic × environmental factors together account for 100 % of phenotype variance.

Chamorro-Premuzic & Furnham (2006)

Suggested Conscientiousness partly develops from interactions between innate abilities and environmental demands.

Flynn Effect

Generational increase in IQ scores observed across many nations (James R. Flynn).

Fluid Intelligence Gain

Flynn found larger IQ increases for fluid intelligence than for crystallized intelligence.

Shared Environment

Experiences common to family members; plays a smaller role than non-shared environment in most traits.

Non-Shared Environment

Unique individual experiences; greater environmental contributor to personality and intelligence differences than shared environment.