chapter 5: biological aspects of personality

Chapter 5:

Biological Aspects of Personality

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Copyright © 2012 Pearson Education, Inc. All rights reserved.

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


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


Genetic Effects Through TemperamentTemperament

◦Stable individual differences in emotional reactivity

◦Longitudinal studies suggest that characteristics tend to remain stable over time as children mature


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)


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


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


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


Sensation Seeking and Addiction-Proneness


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


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


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


Sexual Identity and HomosexualityInfluences on sexual identity:

◦Bem’s “Exotic Becomes Erotic”

◦Sex Hormones and Experience


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


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


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


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


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


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


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


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


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”


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


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





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





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





Personality psychology begins serious study of the genetic bases of individual behavioral patterns

2000s Human genome is unraveled; new ethical challenges arise


The Biological ApproachQuick Analogy

◦Humans as a bundle of genes, brains, and hormones


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


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


The Biological ApproachView of Free Will

◦Behavior is determined by biological tendencies


The Biological ApproachCommon Assessment Techniques

◦Neuroscience, heritability studies, physiological measures


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.


chapter 5: biological aspects of personality

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