1 Psychology 305A: Personality Psychology February 6 Lecture 9.

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Psychology 305A: Personality Psychology

February 6

Lecture 9

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Scoring Your Questionnaire: BAS/BIS

1. Reverse score items 10 and 19 (change response options as follows: 4 1, 3 2, 2 3, 1 4).

2. Sum the following items:

• 1, 4, 7, 10, 12, 15, 19 • 2, 3, 5, 6, 8 • 9, 11, 13, 18 • 14, 16, 17, 20

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The Biological Perspective

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3. What personality characteristics are heritable?

1. What are the goals of behavioural genetics?

2. What are heritability and environmentality and how are they assessed?

A little R&R ….(Review and Reflect)

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3. contrast adoption studies and twin studies.

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By the end of today’s class, you should be able to:

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2. define the terms heritability and environmentality.

1. review the goals of behavioural genetics.

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6. discuss the heritability of diverse personality characteristics.

5. identify temperaments proposed in the literature.

4. discuss criticisms of adoption studies and twin studies.

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What are the goals of behavioural genetics?

• Goal 1: To determine the degree to which individual differences in personality characteristics are caused by genetic factors versus environmental factors:

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VP = VG + VE

VP = Variation in an observable personality characteristic within a population.

VG = Variation in the genetic factors that contribute to that characteristic.

VE = Variation in the environmental factors that contribute to that characteristic.

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• Goal 2: To identify the genetic factors that contribute to individual differences in specific personality characteristics.

E.g., the gene D4DR on chromosome 11 contributes to individual differences in “sensation seeking” (also referred to as novelty seeking).

• Goal 3: To identify the environmental factors that contribute to individual differences in specific

personality characteristics.

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• Heritability: The proportion of phenotypic variance that is attributable to genotypic variance.

What are heritability and environmentality and how are they assessed?

Phenotypic variance: Individual differences in an observable characteristic (e.g., height, aggression, extraversion).

Genotypic variance: Individual differences in genetic makeup.

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• E.g.,

Heritability of aggression = .67.

Indicates that 67% of the observed variance in aggression within a population is due to individual differences in genetic makeup.

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• Environmentality: The proportion of phenotypic variance that is attributable to variance in environmental factors.

• E.g.,

Environmentality of ambition = .62.

Indicates that 62% of the observed variance in ambition within a population is due to individual differences in environmental factors.

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• Heritability and environmentality are assessed using 2 methods:

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1. Adoption Studies

Examine whether adopted children are more similar to their biological parents than their adoptive

parents with respect to a given characteristic.

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For a given personality characteristic, two correlations are calculated:

r2: The correlation between participants’ scores and the scores of their adoptive parents on the characteristic (reflects the influence of shared environment).

r1 > r2 indicates that the personality characteristic is heritable.

r1: The correlation between participants’ scores and the scores of their biological parents on the characteristic (reflects the influence of shared genes).

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2. Twin Studies

Examine whether monozygotic (MZ) twins are more similar than dizygotic (DZ) twins with respect to a given characteristic.

MZ twins share 100% of the same genes; DZ twins share 50% of the same genes.

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A more powerful means by which to assess heritability and environmentality.

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For a given personality characteristic, two correlations are calculated:

r2: The correlation between DZ twins on the characteristic (reflects a small degree of genetic overlap).

r1 > r2 indicates that the personality characteristic is heritable.

r1: The correlation between MZ twins on the characteristic (reflects a large degree of genetic overlap).

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E.g., Dominance:

r1 = .57 (MZ twins)

r2 = .12 (DZ twins)

Heritability = 2 (r1–r2)

Environmentality = (1.00–heritability)

= 2 (.57–.12) = .90

= 1.00-.90 = .10

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What personality characteristics are heritable?

Temperaments

• Temperaments: Personality characteristics that appear during the 1st year of life, persist across the lifespan, have a pervasive influence on behaviour, and are highly heritable.

• Buss and Plomin (1984) identified 3 temperaments:

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1. Activity level: Degree to which an individual expends physical energy through motor activity (i.e., intensity of behaviour, speed of action).

2. Sociability: Degree to which an individual prefers to be with others rather than be alone.

3. Emotionality: Degree to which an individual becomes physiologically aroused in upsetting situations. Comprised of 3 components: anger, distress, and fear.

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EAS Temperament Survey

Score on items:

• 2, 7, 10, 17 = Activity Level

• 1, 6, 15, 20 = Sociability

• 5, 8, 13, 18 = Emotionality: Anger

• 4, 9, 11, 16 = Emotionality: Distress

• 3, 12, 14, 19 = Emotionality: Fear

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EAS Temperament Survey Means and Standard Deviations (Naerde et al., 2004), N = 939

Mean SD

Activity level 3.10 .69

Sociability 3.76 .60

Emotionality: Anger 2.94 .69

Emotionality: Distress 2.33 .72

Emotionality: Fear 2.22 .60

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• Heritability statistics (Wlodzimierz et al.,2003):

Activity level: .58

Sociability: .42

Emotionality—Anger: .62

Emotionality—Distress: .54

Emotionality—Fear: .70

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• Other temperaments proposed in the literature:

Effortful control/impulsivity (e.g., Kochanska & Knaack, 2003).

Approach/avoidance (e.g., Rothbart et al., 2001; Eisenberg et al., 2004).

Intelligence (e.g., Plomin, 1989).

Behavioural inhibition (i.e., shyness; e.g., Kagan, 2011; Kagan & Snidman, 1991).

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The Big 5 dimensions

• Heritability statistics (Jang et al., 1998; see also Yamagata et al., 2006):

Extraversion: .50

Agreeableness: .48

Conscientiousness: .49

Neuroticism: .49

Openness to Experience: .48

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Personality disorders

• Heritability statistics (Coolidge et al., 2001):

Avoidant personality disorder: .61

Borderline personality disorder: .76

Histrionic personality disorder: .79

Narcissistic personality disorder: .66

Obsessive-compulsive personality disorder: .77

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• Heritability statistics (Blonigen et al., 2003; Bouchard et al., 1990; Tellegen et al., 1988):

Fearlessness ………………………………………… > .95

Carefree Nonplanfulness (i.e., impulsiveness)……... .94

Machiavellianism (i.e., enjoys manipulating others)... .74

Social potency (i.e., skilled at influencing others) …. .66

Aggressiveness ……………………………………….. .67

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Psychopathy

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• Heritability statistics (Bouchard et al., 1990; Tellegen et al., 1988)

Creativity or imagination …………………………. .74

Sense of alienation …………………………......... .59

Traditionalism ………………………………….….. .59

Low risk taking …………………………………….. .45

Achievement orientation …………………............ .38

Other personality characteristics

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3. contrast adoption studies and twin studies.

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By the end of today’s class, you should be able to:

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2. define the terms heritability and environmentality.

1. review the goals of behavioural genetics.

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6. discuss the heritability of diverse personality characteristics.

5. identify temperaments proposed in the literature.

4. discuss criticisms of adoption studies and twin studies.