chapter 5: biological aspects of personality
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Direct Genetic Effects Natural selection and functionalism Natural selection the process by which adaptive characteristics emerge over generations includes behavioral tendencies and emotions—"personality“ 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 Copyright © 2012 Pearson Education, Inc. All rights reserved.TRANSCRIPT
Chapter 5:
Biological Aspects of Personality
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Direct Genetic EffectsNatural selection and
functionalism◦Natural selection
the process by which adaptive characteristics emerge over generations
includes behavioral tendencies and emotions—"personality“
◦Evolutionary personality theory Modern application of Darwin’s ideas to
individual differences in personality Attention is focused on the function of a
characteristic in survivalCopyright © 2012 Pearson Education, Inc. All rights reserved.
Direct Genetic EffectsExample: Angelman Syndrome
◦A congenital (inborn) disorder caused by a defect on chromosome 15
◦Happy, cheerful, attractive, friendly◦Mental retardation and jerky movement◦Demonstrates how genetic factors set
before birth can dramatically influence later personality
Example: Williams Syndrome◦Excessively sociable, limited intellect
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Direct Genetic EffectsBehavioral Genomics
◦The study of how genes affect behavior
◦How human genes, evolved through variation and natural selection, function together with each other and the environment to influence behavior
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Genetic Effects Through TemperamentTemperament
◦Stable individual differences in emotional reactivity
◦Longitudinal studies suggest that characteristics tend to remain stable over time as children mature
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Genetic Effects Through Temperament
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)
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Eysenck’s ModelLinks the introversion-
extroversion dimension to the underlying nervous system◦Extroverts have a low level of brain
arousal, and so seek out stimulation◦Introverts have a higher level of
internal arousal, and so they tend to shy away from stimulating social environments
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Approach, Inhibition, and Regulation: Jeffrey GrayTwo relevant biological systems
◦Behavioral inhibition system (BIS) Provides the orienting response to novel
situations and also responds to things that are punishing
Overactiveanxiety◦Behavioral activation system
(Behavioral approach system; BAS) Regulates our response to rewards Overactiveimpulsivity
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Sensation Seeking and Addiction-Proneness
Zuckerman's theory ◦ those high on "sensation seeking"
have a low level of internal arousal, so they are drawn to novel and exciting experiences
◦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
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Sensation Seeking and Addiction-Proneness
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Twins as a Source of DataComparing identical twins to
fraternal twins makes it possible to detect genetic influences on personality
Minnesota Twin Study◦Has found impressive similarities in
personality between people who have the same genetic make up
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Twins as a Source of DataStill unclear how much of the
similarity is genetically pre-programmed and how much is due to the shared and nonshared environment
Nonshared environmental variance arises from features of the environment that children raised in the same home experience differently
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The Case of SchizophreniaTwin studies have helped to show
that schizophrenia is genetically influenced◦Structural abnormalities have been
found in the brains of schizophrenics◦There is a “genetic predisposition” to
schizophreniaHowever, it is not simply a
genetic disease◦Concordance between identical
twins is far from perfectCopyright © 2012 Pearson Education, Inc. All rights reserved.
Sexual Identity and Homosexuality
Twin studies have shown that homosexuality has a genetic influence
However, there appear to be some environmental influences as well
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Sexual Identity and HomosexualityInfluences on sexual identity:
◦Bem’s “Exotic Becomes Erotic”
◦Sex Hormones and Experience
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Mediated Effects of Biology
Effects through environmental toxins◦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
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Mediated Effects of BiologyEffects through physical illness
◦Personality can sometimes drastically change as a result of Alzheimer’s disease Strokes Temporal lobe epilepsy Various surgical procedures Pick’s disease
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Mediated Effects of BiologyEffects from legal and illegal drugs
◦ Widely prescribed drugs such as tranquilizers (like Valium), sleeping pills (like Halcion), and various antidepressants have short-term and sometimes long-term effects on personality
◦ Cocaine tends to produce symptoms of paranoia. Users may worry, become obsessed with details, and feel they are being persecuted
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Effects from the Creation of Environments
Biology can affect personality by affecting the environments in which we find ourselves
Tropisms◦The processes by which some
individuals grow towards more fulfilling and health-promoting spaces while other individuals remain subject to darker, health-threatening environments
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Effects from the Creation of Environments
Characteristics that are genetically based (density of tongue papillae) can lead to behaviors and preferences that shape personality in differing directions
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Do Looks Reveal Personality?Somatotypes
Three body types (Sheldon)◦Mesomorphs
muscular, large-boned athletic types◦Ectomorphs
slender, bookworm types◦Endomorphs
roly-poly, supposedly good-natured, typesOverly simplistic, but there may
be some metabolic or physiological link
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Effects from Reactions of OthersPhysical characteristics influence
the way others treat us and thereby mold our views of the world—our “personalities”
Physical Attractiveness Stereotypes◦People tend to expect attractive
people to do good and be good◦Adults have higher expectations for
attractive childrenCopyright © 2012 Pearson Education, Inc. All rights reserved.
SociobiologyThe scientific study of the influence of
evolutionary biology on an organism's responses regarding social matters
Derives from study of animal behavior
Most commonly applied to human aggression, human courtship, and human family relations
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SociobiologyCinderella Effect
◦Refers to evidence suggesting that parents give preference to biological children over step-children
◦Sociobiologists suggest that this results from natural selection, in which parents have evolved to give preference and protection to their biological children, who carry their genes
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Personality and Public PolicyMisuses of knowledge regarding
genetics◦Social Darwinism and the “right” to
dominate/kill others based on survival of the fittest
◦Eugenics “Improve” the gene pool by sterilizing poor
people◦Immigration laws (early 20th century in
the US) to limit the population of “undesirables”
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Personality and Public PolicyMisuses of knowledge regarding
genetics◦Nazi dream of a "master race" and
genocide◦The Human Genome Project—what
are the implications?◦Eugenics and forced sterilization of
various groups
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Timeline:The Biological Approach
Developments in Biological Aspects
Societal and Scientific Context
Charles Darwin publishes On the Origin of Species by Means of Natural Selection
1850s -1880s
Biology adopts evolutionary paradigm
Francis Galton studies families and twins, beginning the biological study of individual differences
1860s-1890s
Development of the field of genetics, but Social Darwinism misappropriates ideas
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Timeline:The Biological Approach
Developments in Biological Aspects
Societal and Scientific Context
Studies of temperament and individual constitution begin
1940s-1960s
Psychology is dominated by behaviorist and other non-biological approaches
Hans Eysenck proposes brain-based model of personality
1960s-1970s
Hormones, temperament, and brain neurotransmitters begin to receive significant attention
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Timeline:The Biological Approach
Developments in Biological Aspects
Societal and Scientific Context
Studies of effects on the brain of drug abuse, pollution, and genetic diseases begin in earnest
1980s Fields of environmental toxicology and psychopharmacology develop
Evolutionary personality psychology takes root
1990s More sophisticated views of genetics and evolution develop
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Timeline:The Biological Approach
Developments in Biological Aspects
Societal and Scientific Context
Personality psychology begins serious study of the genetic bases of individual behavioral patterns
2000s Human genome is unraveled; new ethical challenges arise
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The Biological ApproachQuick Analogy
◦Humans as a bundle of genes, brains, and hormones
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The Biological ApproachAdvantages
◦Emphasizes the limits imposed by genetics and bodily endowment on personality
◦Acknowledges the effects of biological influences on the reactions of others and the environments that individuals choose
◦Can be combined with other approaches
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The Biological ApproachLimits
◦Minimizes human potential for growth and change
◦Danger of misuse by those who oversimplify its findings
◦Uses biological concepts, which may not be appropriate for psychological phenomena
◦Difficult to capture consciousness
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The Biological ApproachView of Free Will
◦Behavior is determined by biological tendencies
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The Biological ApproachCommon Assessment Techniques
◦Neuroscience, heritability studies, physiological measures
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The Biological ApproachImplications for Therapy
◦Since behavior is seen as resulting from evolved biological structures, therapy is focused on biological interventions: psychotropic drugs like Prozac or Valium for
mental “illness” hormones for conditions such as PMS irritability antihistamines or cleaner environments for
allergy- and toxin-related conditions◦Eventually, gene therapies may be
commonplace, with the attendant moral dangers.
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