© 2013 W. W. Norton & Company, Inc. The Personality Puzzle Sixth Edition by David C. Funder Chapter 9: The Inheritance of Personality: Behavioral Genetics and Evolutionary Theory Slides created by Tera D. Letzring Idaho State University 1

© 2013 W. W. Norton & Company, Inc. Genetics! May determine where you start but what happens from there depends on many things (including you) 2

© 2013 W. W. Norton & Company, Inc. Behavioral Genetics Attempts to explain individual differences in personality traits Examines how genes influence patterns of behavior 3

© 2013 W. W. Norton & Company, Inc. Heritability coefficient – the percentage of the variance of a trait that is controlled by genetic factors (proportion from 0.0 – 1.00) This tells us nothing about an individual but it is about the differences within a group 4

© 2013 W. W. Norton & Company, Inc. 100% heritable – only genetic factors 5 Heritability

© 2013 W. W. Norton & Company, Inc. Heritability 6

© 2013 W. W. Norton & Company, Inc. Heritability Environment One Environment Two 7

© 2013 W. W. Norton & Company, Inc. Calculating Heritabilities Compare similarity in personality between people who are and are not related and people who are related to different degrees – Monozygotic (MZ) vs. dizygotic (DZ) twins 8

© 2013 W. W. Norton & Company, Inc. Calculating Heritability r = 0.6 r = 0.3 r =

© 2013 W. W. Norton & Company, Inc. What Heritabilities Tell You 1.Not all of personality is based on experience 2. Some human characteristics are more likely due to environmental inputs (severe mental retardation vs colour blindness) 3. Non-shared environment has a great impact on personality ie) friendships, interests and activities 10

© 2013 W. W. Norton & Company, Inc. When the heritability of a given trait is greater than 0 (which it nearly always is) then the trait is affected by genetic factors in some way. 11 What Heritabilities Tell You

© 2013 W. W. Norton & Company, Inc. How Genes Affect Personality Gene-environment interactions – Epigenetics! – Environments can determine how or whether a gene is expressed – Even highly heritable traits can be modified by the environment – cgI (4 min) cgI 12

© 2013 W. W. Norton & Company, Inc. How Genes Affect Personality Behavioural genetics increasingly uses molecular biology Molecular genetics – There are two versions of the 5-HTT gene (long and short) – People with the short 5-HTT gene show decreased serotonin function and stronger responses in the amygdala – Greater risk for anxiety disorders and higher neuroticism scores 13

© 2013 W. W. Norton & Company, Inc. How Genes Affect Personality Gene-environment interactions – Genes are not causal – People with the short 5- HTT gene appear to be at risk for depression and antisocial behavior, but only if they experience severe stress or maltreatment in childhood. 14

© 2013 W. W. Norton & Company, Inc. How Genes Affect Personality MAOA gene: affects neurotransmitter functioning and is associated with increased aggression Caspi et al (2002) studied four groups 15 Gene + abuse No gene + abuse Gene + no abuse No gene + no abuse

© 2013 W. W. Norton & Company, Inc. Antisocial behaviour 16

© 2013 W. W. Norton & Company, Inc. Antisocial behaviour 17

© 2013 W. W. Norton & Company, Inc. Behavior Genetics: The Future The fact that genes are important determinants of personality is already well- established Researchers are working to find out which genes are associated with personality 18

© 2013 W. W. Norton & Company, Inc. Sensation-Seeking If you new that your child was born with a gene characteristic of sensation-seeking, what would you do? 19

© 2013 W. W. Norton & Company, Inc. Evolutionary Personality Psychology Attempts to explain how patterns of behavior that characterize all humans originated in the survival value of these characteristics Evolution and behavior Identify common behavior patterns and then determine how the behavior was adaptive 20

© 2013 W. W. Norton & Company, Inc. Evolutionary Psychology What is the most extreme thing you have done to be accepted in to a group or by another person? – Bullying – Hazing – Changing appearance – Illegal behaviour 21

© 2013 W. W. Norton & Company, Inc. Evolutionary Personality Psychology Rejection is painful and causes depression Depression : pain signals something is wrong and must be fixed Anti-depressants may lead to people remaining in negative life situations 22

© 2013 W. W. Norton & Company, Inc. Mating Behaviour In selecting someone to form a romantic relationship with, which do you value more? a)Physical attractiveness b)Financial security 23

© 2013 W. W. Norton & Company, Inc. Evolutionary Personality Psychology Mate selection/Attraction – Men place higher value on physical attractiveness and prefer younger mates – Women place higher value on economic security and prefer older mates – Both want the highest likelihood of healthy offspring who will survive and reproduce 24

© 2013 W. W. Norton & Company, Inc. Evolutionary Personality Psychology Mate selection: some complications – Women who are too thin cannot bear children – Larger women used to be considered to be ideal – Attraction is influenced by more than physical characteristics – Male physical attractiveness is more important to women than it should be 25

© 2013 W. W. Norton & Company, Inc. Evolutionary Personality Psychology Mating strategies – Differences between men and women: desired number of sexual partners, faithfulness to partner, selectivity of partners; explained by differences in factors that affect reproductive success – BUT once an attachment is formed, both have an interest in maintaining it 26

© 2013 W. W. Norton & Company, Inc. Evolutionary Personality Psychology Mating strategies: Jealousy 27

© 2013 W. W. Norton & Company, Inc. Evolutionary Personality Psychology Focus has been on general human nature Evolutionary reasons for individual differences – Diversity is necessary for survival of the species Human nature is flexible – Prefrontal cortex can mediate any evolutionary (reproductive) instincts 28

© 2013 W. W. Norton & Company, Inc. Change in Income and Educational Differences 29

© 2013 W. W. Norton & Company, Inc. Think About It If you are a woman, would you be comfortable marrying a man who had less education and made less money than you? If you are a man, would you be comfortable marrying a woman who had more education and made more money than you? Why? Are these attitudes changing? 30