Chapter 5: Biological Aspects of Personality. Copyright Allyn & Bacon (2009)

Transcription

1 Chapter 5: Biological Aspects of Personality

2 Direct Genetic Effects Natural selection and functionalism Natural selection the process by which adaptive characteristicsemerge over generations Attention is focused on the functionof a characteristic in survival Evolutionary personality theory (EPT) Modern application of Darwin s ideas to individual differences in personality EPT : applying biological evolutionary theory to human personality

3 Direct Genetic Effects Example: 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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5 Direct Genetic Effects Behavioral 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

6 Chromosome, genes and Deoxy Nucleic Acid (DNA)

7 Genetic Effects Through Temperament Study of Temperaments-Based on Work of Pavlov Temperament Stable individual differences in emotional reactivity Different nervous system responses to unpleasant stimuli Longitudinal studies suggest that characteristics tend to remain stable over time as children mature

8 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)

9 Eysenck s Model of Nervous System Temperament Links the introversion-extroversion dimension to the underlying nervous system Extroverts have a low levelof 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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11 Approach, Inhibition, and Regulation: Jeffrey Gray Two relevant biological systems Behavioral inhibition system Provides the orienting response to novel situations and also responds to things that are punishing Overactive anxiety Behavioral activation system (Behavioral approach system) Regulates our response to rewards Overactive impulsivity

12 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

13 DOPAMINE The various chemicalsin the brain have a special balance that is required for humans to function properly. Dopamine is just one of those chemicals. Too much or too little dopamine can have devastating results. Dopamine is necessary for people to function properly. Dopamine is a neurotransmitter that assists the body in regulating movements and emotions. A neurotransmitter passes signals between cells within the brain.

14 Twins as a Source of Data Comparing 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

15 Sir Francis Galton Supposition that Upper Class Englishmen were a superior population Began the study of adoptive twins Began the eugenics movement (good birth or good genes) Encouraged eminent families to have lots of children to improve the human blood lines

16 Twins as a Source of Data Still unclear how much of the similarity is genetically pre-programmed and how much is due to the shared and nonshared environment Nonshared environmental variancearises from features of the environment that children raised in the same home experience differently

17 The Case of Schizophrenia Twin 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 schizophrenia However, it is not simply a genetic disease Concordance between identical twins is far from perfect

18 Sexual Identity and Homosexuality Twin studies have shown that homosexuality has a genetic influence However, there appear to be some environmental influences as well

19 Sexual Identity and Homosexuality Influences on sexual identity: Bem s Exotic Becomes Erotic Kin Selection Sex Hormones and Experience

20 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

21 Mediated Effects of Biology Effects 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

22 Mediated Effects of Biology Effects 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

23 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

24 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, types Overly simplistic, but there may be some metabolic or physiological link

25 ENDOMORPH Psychologically, the endomorph is: Sociable Fun-loving Love of food Tolerant Even-tempered Good humored Relaxed With a love of comfort And has a need for affection

26 MESOMORPH Psychologically, they are: Adventurous Courageous Indifferent to what others think or want Assertive/bold Zest for physical activity Competitive With a desire for power/dominance And a love of risk/chance

27 ECTOMORPH Psychologically they are: Self-conscious Private Introverted Inhibited Socially anxious Artistic Intense Emotionally restrained Thoughtful

28 Effects from Reactions of Others Physical 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 children

29 Sociobiology The 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

30 Sociobiology Cinderella Effect Refers to evidence suggesting that parents give preference to biological children over stepchildren 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

31 Personality and Public Policy Misuses 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 20 th century in the US) to limit the population of undesirables

32 Personality and Public Policy Misuses 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

33 Timeline: The Biological Approach Developments in Biological Aspects Charles Darwin publishes On the Origin of Species by Means of Natural Selection Francis Galton studies families and twins, beginning the biological study of individual differences 1850s s 1860s- 1890s Societal and Scientific Context Biology adopts evolutionary paradigm Development of the field of genetics, but Social Darwinism misappropriates ideas

34 Timeline: The Biological Approach Developments in Biological Aspects Studies of temperament and individual constitution begin Hans Eysenck proposes brain-based model of personality 1940s- 1960s 1960s- 1970s Societal and Scientific Context Psychology is dominated by behaviorist and other non-biological approaches Hormones, temperament, and brain neurotransmitters begin to receive significant attention

35 Timeline: The Biological Approach Developments in Biological Aspects Studies of effects on the brain of drug abuse, pollution, and genetic diseases begin in earnest Evolutionary personality psychology takes root 1980s 1990s Societal and Scientific Context Fields of environmental toxicology and psychopharmacology develop More sophisticated views of genetics and evolution develop

36 Timeline: The Biological Approach Developments in Biological Aspects Personality psychology begins serious study of the genetic bases of individual behavioral patterns 2000s Societal and Scientific Context Human genome is unraveled; new ethical challenges arise

37 The Biological Approach Quick Analogy Humans as a bundle of genes, brains, and hormones

38 The Biological Approach Advantages 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

39 The Biological Approach Limits 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

40 The Biological Approach View of Free Will Behavior is determined by biological tendencies

41 The Biological Approach Common Assessment Techniques Neuroscience, heritability studies, physiological measures

42 The Biological Approach Implications 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