Psychology 3051 Psychology 305A: Theories of Personality Lecture 8 1

2 Annoucements 1. The grades for the first midterm exam are now available on the course website. The mean score on the midterm exam was 68% (SD = 14%, range = 20% – 96%).

3 2. The TAs will hold extra office hours for interested students to review their exams: Kate (A-M): Tuesday, October 11 th, 2:00-3:00 (regular office hour, Kenny 3526) Thursday, October 13 th, 1:00-2:00, 3:00-4:00 (Kenny 1906) Lauren (N-Z): Wednesday, October 12 th, 12:00-2:00 (Kenny 3522) Monday, October 17 th, 1:00-2:00 (regular office hour, Kenny 3522)

Psychology 3054 The Biological Perspective 4 1. What are the goals of behavioural genetics? (continued) 2. What are heritability and environmentality and how are they assessed? 3. What personality characteristics are heritable?

2. describe distinct genotype-environment correlations. 4. contrast family studies, adoption studies, and twin studies review the goals of behavioural genetics. 3. define the terms “heritability” and “environmentality.” By the end of today’s class, you should be able to:

6 6. identify distinct temperaments. 7. discuss the heritability of diverse personality characteristics. 5. identify the shortcomings of family studies, adoption studies, and twin studies.

Psychology 3057 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 as opposed to environmental factors: 7

Psychology 3058 V P = V G + V E V P = Variation in an observable personality characteristic within a population. V G = Variation in the genetic factors that contribute to that characteristic. V E = Variation in the environmental factors that contribute to that characteristic. 8

Psychology 3059 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.” Goal 3: To identify the environmental factors that contribute to individual differences in specific personality characteristics. 9

Psychology 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. 10

Psychology 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. 11

Psychology 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. 12

Psychology Heritability and environmentality are assessed using 3 methods: 1. Family Studies  Examine whether participants are more similar to immediate family members than distant family members with respect to a given characteristic. 13

Psychology Proportion of genes shared Parents and children Non-twin siblings Grandparents and grandchildren Aunts/uncles and nieces/nephews First cousins 50% 25% 12.5% 14

Psychology  For a given personality characteristic, two correlations are calculated: r 2 : The correlation between participants’ scores and the scores of their distant family members on the characteristic (reflects small degree of genetic overlap). r 1 : The correlation between participants’ scores and the scores of their immediate family members on the characteristic (reflects large degree of genetic overlap).  r 1 > r 2 indicates that the personality characteristic is heritable. 15

Psychology Adoption Studies  Examine whether adopted children are more similar to their biological parents than their adoptive parents with respect to a given characteristic.  A more powerful means by which to assess heritability and environmentality. 16

Psychology  For a given personality characteristic, two correlations are calculated: r 2 : The correlation between participants’ scores and the scores of their adoptive parents on the characteristic (reflects the influence of shared environment).  r 1 > r 2 indicates that the personality characteristic is heritable. r 1 : The correlation between participants’ scores and the scores of their biological parents on the characteristic (reflects the influence of shared genes). 17

Psychology Twin Studies  Examine whether monozygotic (MZ) twins are more similar than dizygotic (DZ) twins with respect to a given characteristic.  The most powerful means by which to assess heritability and environmentality.  MZ twins share 100% of the same genes; DZ twins share 50% of the same genes. 18

Psychology  For a given personality characteristic, two correlations are calculated: r 2 : The correlation between DZ twins on the characteristic (reflects a small degree of genetic overlap).  r 1 > r 2 indicates that the personality characteristic is heritable. r 1 : The correlation between MZ twins on the characteristic (reflects a large degree of genetic overlap). 19

Psychology  E.g., Dominance: r 1 =.57 (MZ twins) r 2 =.12 (DZ twins) Heritability = 2 (r 1 –r 2 ) Environmentality = (1.00–heritability) 90% of variance in dominance is due to individual differences in genetic makeup; 10% of variance in dominance is due to individual differences in environmental factors. = 2 (.57–.12) =.90 = =.10 20

Psychology What personality characteristics are heritable? Temperaments Temperaments: Personality characteristics that appear during the 1 st year of life, persist across the lifespan, have a pervasive influence on behaviour, and are highly heritable. Buss and Plomin (1984) identified 3 temperaments: 21

Psychology 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. 22

Psychology 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 23

Psychology EAS Temperament Survey Means and Standard Deviations (Naerde et al., 2004), N = 939 MeanSD Activity level Sociability Emotionality: Anger Emotionality: Distress Emotionality: Fear

Psychology Heritability statistics (Wlodzimierz et al.,2003): Activity level:.58 Sociability:.42 Emotionality—Anger:.62 Emotionality—Distress:.54 Emotionality—Fear:.70 25

26 Other temperaments proposed in the literature: Effortful control/Impulsivity. Approach/avoidance. Intelligence.

Psychology The Big 5 Dimensions Heritability statistics (Jang et al., 1998): Extraversion:.50 Agreeableness:.48 Conscientiousness:.49 Neuroticism:.49 Openness to Experience:.48 27

Psychology Personality Characteristics Related to Psychopathy Heritability statistics (Blonigen et al., 2003; Bouchard et al., 1990; Tellegen et al., 1988): Fearlessness ………………………………………… >.95 Carefree Nonplanfulness (i.e., impulsiveness)…… Machiavellianism (i.e., enjoys manipulating others) Social potency (i.e., skilled at influencing others) …..66 Aggressiveness ………………………………………

Psychology Heritability statistics (Bouchard et al., 1990; Tellegen et al., 1988) Creativity or imagination ………………………..….74 Sense of alienation ………………………… Traditionalism ………………………………….… Low risk taking ……………………………………...45 Achievement orientation ………………… Other Personality Characteristics 29

Psychology The Biological Perspective What are the goals of behavioural genetics? (continued) 2. What are heritability and environmentality and how are they assessed? 3. What personality characteristics are heritable?