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PSY 235 (11)
Chapter 5

Chapter 5

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PSY 235
Taryn Aldrich

Chapter 5 Biological aspects of personality Direct Genetic Effects • Natural selection and functionalism o Natural selection  The process by which adaptive characteristics emerge over generations  Includes behavioral tendencies and emotions- “personality” o Evolutionary personality theory  Modern application of Darwin’s ideas to individual differences in personality  Attention is focused on the function of a characteristic in survival o Example: Angelman Syndrome  A congenital disorder caused by a defect in chromosome 15  Happy, cheerful, attractive, friendly  Mental retardation and jerky movement  Demonstrates how genetic factors set before birth can dramatically influence later personality o Example: Williams Syndrome  Excessively sociable, limited intellect • Behavioral Genomes o The study of how genes effect human behavior o How human genes, evolved through variation and natural selection, function together with each other and the environment to influence behavior • Genetic Effects Through Temperament o Temperament  Stable individual differences in emotional reactivity  Longitudinal studies suggest that characteristics tend to remain stable over time as children mature o Four basic aspects of temperament  Activity • Vigorous motion (vs passivity)  Emotionality • Easily aroused (vs calm and stable)  Sociability • Approaches and enjoys others (vs aloof)  Impulsivity • Aggressive and cold (vs conscientious and friendly) Eyseneck’s Model • Links the introversion-extroversion dimension to the underlying nervous system o Extroverts have a low level of brain arousal, and so seek out stimulation o Introverts have a higher level of internal arousal, and so they tend to shy away from stimulating social environments Sensation seeking and addiction proneness • Zuckerman’s theory o Those high on “sensation seeking” have a low level of internal arousal, so they are drawn to novel and exciting experiences o It is likely that some people have natural defects or disease-caused weaknesses in their dopamine systems, and such people may be unusually susceptible to addiction Twins as a source of data • Comparing identical twins to fraternal twins make it possible to detect genetic influences on personality • Minnesota twin study o Has found impressive similarities in personality between people who have the same genetic make up • Still unclear how much of the similarity is genetically pre-programmed and how much is due to the shared and non-shared environment • Non-shared environmental variance arises from features of the environment that children raised in the same home experience differently The case of Schizophrenia • Twin studies have helped to show that schizophrenia is genetically influenced o Structural abnormalities have been found in the brains of schizophrenics o There is a “genetic predisposition” to schizophrenia • However, it is not simply a genetic disease o Concordance between identical twins is far from perfect Sexual Identity and Homosexuality • Twin studies have shown that homosexuality has a genetic influence • However, there appear to be some environmental influences as well Mediated effects of biology • Effects through environmental toxins o Poisoning  “Mad as a hatter”- hat makers suffered brain damage when exposed to mercury in hat making factories  Lead poisoning and cognitive/ behavioral deficits in children  Manganese miners and fighting behavior o Effects through physical illness  Personality can sometimes drastically change as a result of • Alzheimer’s disease
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