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DeservingPoplar

Uploaded by DeservingPoplar

University of Victoria

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personality nature vs nurture genetics psychology

Summary

This document discusses the biological factors influencing personality, focusing on nature versus nurture, genetic influence, and the role of the environment. It examines twin studies, brain structures, and neurotransmitters. The text also explores epigenetics, a field that investigates how environmental influences impact gene expression. It provides insights into various aspects of personality development.

Full Transcript

Nature vs. Nurture - ​ Nature (Genetics): One aspect of biological influence on personality, but only a small part. ​ Nurture (Environment): Anything occurring after birth that shapes personality. ○​ Shared Environment: Factors common among individuals raised in the same...

Nature vs. Nurture - ​ Nature (Genetics): One aspect of biological influence on personality, but only a small part. ​ Nurture (Environment): Anything occurring after birth that shapes personality. ○​ Shared Environment: Factors common among individuals raised in the same family. ○​ Non-Shared Environment: Unique experiences that differ between individuals. ​ Biology Beyond Genetics: Includes all influences on our body, whether genetic, environmental, or a combination of both (e.g., brain shaped by genes but also altered by experience). The Heritability of Personality: Twin Studies ​ Monozygotic (Identical) Twins: Share identical genetic profiles, making them ideal for genetic influence studies. ​ Percentage of Variance: Explains how much genetic vs. environmental factors contribute to personality differences within a group, not individuals. ○​ ~50% of personality differences are attributed to genetics, 50% to environmental factors. Heritability Estimates Big Five Personality Traits ​ Neuroticism: ~41% genetic influence ​ Openness: ~61% genetic influence ​ Non-shared environmental effects: 39%-59% HEXACO Model ​ Openness: ~63% genetic influence ​ Honesty-Humility: ~46% genetic influence ​ Only trait significantly shaped by shared environment: 37% of variance in Honesty-Humility attributed to shared upbringing. Non-Shared Environmental Influences ​ Neuroticism: Shaped by how siblings perceive the family environment. ​ Conscientiousness: Influenced by how siblings perceive parental affection and control. Gene-Environment Interactions ​ Genetics and environment work together, not independently. ​ Gene Expression: Determines how much genes influence traits or outcomes. ​ Environmental Factors Affect Genetic Expression: ○​ Epigenetics: The study of how external factors (e.g., stress, diet) modify gene expression. ○​ Example: A difficult-to-soothe baby can create a stressful environment, which then influences both child and caregiver. ○​ Stress and childhood trauma can alter genetic expression, influencing personality traits. ○​ Phenotype: Observable traits (appearance and behavior) are shaped by both genes and environment. Epigenetics: How Environment Influences Genes ​ Epigenetic Marks: Chemical modifications on chromatin (a complex of DNA and proteins) that turn genes on or off. ○​ Unravelling chromatin = turns genes on ○​ Ravelling chromatin = turns genes off ​ Key Insights: ○​ Multi-species studies suggest epigenetic mechanisms are similar in humans. ○​ Some epigenetic marks can be inherited across generations. ○​ Healthy lifestyle choices (diet, stress reduction) can positively impact epigenetic markers for future generations. ○​ Epigenetic changes can be reversible—potential for drugs to treat diseases like cancer by altering gene expression. Epigenetic Evidence from Animal Studies ​ Agouti Mouse Study: ○​ Mice with an active Agouti gene are yellow and obese. ○​ A healthy maternal diet can deactivate this gene, leading to normal-weight offspring. ○​ Poor maternal health (e.g., smoking, poor diet) increases offspring risk for cardiovascular disease, obesity, asthma, etc. Brain Structures and Personality - Frontal Lobe ​ Associated with high agreeableness → Individuals with high agreeableness show increased activation in the frontal lobe. ​ Involved in conscious decision-making and processing social information. Amygdala ​ Plays a role in discrepancy detection. ​ High neuroticism → More responsive amygdala, leading to increased sensitivity to surprises. ​ High extraversion → Increased amygdala activation, resulting in stronger responses to reward cues. Ventral Striatum ​ Linked to reward, motivation, habitual behaviors, goal-directed actions, and fear learning. ​ Low conscientiousness → More activity in the ventral striatum. ​ Individuals using substances → Heightened activity in the ventral striatum. Dorsolateral Prefrontal Cortex (DLPFC) ​ Involved in thinking through complex ideas (related to openness to experience), motor memory, and processing intentions. ​ High openness → Associated with increased activity in this region. Right Posterior Middle Temporal Gyrus ​ Openness to experience is linked to this area. ​ Individuals with higher openness have a thicker cortex, which is crucial for memory, cognition, and processing complex topics. The Biology of Personality: Neurotransmitters Dopamine ​ Low conscientiousness & high openness → Associated with higher dopamine levels. ​ People with genes producing more dopamine are prone to risk-taking behaviors. ​ Parkinson’s disease is treated with dopamine. ​ High openness to experience is linked to higher dopamine levels but is mediated by stress. Serotonin ​ Higher serotonin levels lower impulsivity. ​ Low serotonin in one brain region doesn’t mean low serotonin overall. ​ Neurotransmitter levels vary across brain regions. ​ New field of study → No definitive causal relationships established yet. The Biology of Personality: Circadian Rhythm Morning People: ​ Higher conscientiousness and agreeableness. ​ More introverted, less anxious, neater, more caring, and conventional. Evening People: ​ Higher extraversion, neuroticism, and openness to experience. ​ More messy, outgoing, anxious, and open to new ideas. Changes Over Time: ​ Teenagers and young adults → More likely to be evening people. ​ Adults 50+ → More likely to be morning people. ​ Circadian rhythm is influenced by life circumstances and age. Evolution and Personality ​ Explains how evolution shaped human psychology. ​ Humans evolve in response to environments. ​ Many desires and preferences are remnants of hunter-gatherer history. Survival and Reproduction: ​ People act in ways that maximize survival and reproduction. ​ Certain traits have persisted because they helped early humans thrive. Challenges to Evolutionary Explanations: ​ Ignore cultural influences: Culture shapes personality traits in meaningful ways. ​ Impossible to prove: Arguments can be made for any finding. ​ Justifies bad behavior: People might use evolutionary explanations to excuse violence or aggression (e.g., “it’s just part of who we are”). Evolution and Personality: The Need to Belong ​ A universal human motive → All people seek belonging. ​ Rejection can increase hostility and aggression. ​ Social pain activates brain regions associated with physical pain. ​ Acetaminophen (Tylenol) reduces emotional pain, just as it does physical pain. ​ People differ in their level of social interaction needs due to evolutionary adaptations to varying environments

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