The document discusses behavioral genetics, covering methods such as selective breeding, pedigree analysis, and twin studies to explore the influence of heredity on behavior. It provides insights into genetic factors affecting traits like aggression and temperament, as well as the principles of evolutionary psychology related to human nature and mating preferences. The content also critiques the evolutionary perspective for implying genetic determinism and examines sex differences in cognitive functions and behavioral traits.

1. Behavioral Genetics
Brian J. Piper, Ph.D.
1

2. Goals
• Genetics Primer
• Behavioral Genetics Methods
– Selective Breeding
– Pedigree Analysis
– Twins (& Adopted Twins!)
• Evolutionary Psychology
2

3. 3

4. Gregor Mendel
• Austrian friar who studied pea
plants (29K!)
1822-1884
• Dichotomous traits
4
http://www.accessexcellence.org/RC/AB/BC/Gregor_Mendel.php

5. Gregor Mendel
• Homozygote versus Heterozygote
• Dominant versus Recessive 1822-1884
5
http://www.accessexcellence.org/RC/AB/BC/Gregor_Mendel.php

6. Examples of Mendelian Patterns
S = spherical, s = wrinkled
6

7. Huntington’s Disease
• Neurodegenerative
Disease
– Loss of motor function H h
– dementia h Hh hh
h Hh hh
1 min video: http://www.youtube.com/watch?v=JzAPh2v-SCQ 7
http://en.wikipedia.org/wiki/Huntington%27s_Disease

8. Terminology
Chromosomes containing DNA
(deoxyribonucleic acid) are situated in the nucleus
of a cell.
8

9. Genes: Our Codes for Life
Segments within DNA consist of genes that
make proteins to determine our development.
9
Chromosome 4: Huntingtin gene;

10. Pedigree
Rife (1940) collected info from 2,200 college
students and their parents
Parent Child
RXR= 7.6
R x L or L x L = 21.6
Rife (1940) Genetics, 25, 178-186.

11. Aggression
• Brunner described an extended
family in which 5 males had
impulsive aggression including:
– Exhibitionism
– Arson
– Rape
11

12. Limitations of Pedigree
• Paternity
• Best for Dichotomous Characteristics
• Families share environments too
12

13. Selective Breeding
• Simple procedure with extended history
• May involve controlling environment
• Has been completed for emotions and drug
preference
• Limitations:
– Generalizability
– Ethics
13

14. Twin Studies
Studying the effects of heredity and
environment on two sets of twins, identical and
fraternal, has come in handy.
14

15. Logic
Relationship Genetic Relationship Predicted Similarity
Monozygotic Twins 100% High
Dizygotic Twins (same 50% Moderate
sex)
Siblings 25% Lower
Unrelated Minimal Modest
15

16. Logic
Relationship Genetic Relationship Predicted Similarity
Monozygotic Twins 100% High
Dizygotic Twins (same 50% Moderate
sex)
Siblings 25% Lower
Unrelated Minimal Modest
16

17. 17

18. Temperament and Heredity
Temperament refers to a person’s stable
emotional reactivity and intensity. Identical
twins express similar temperaments, suggesting
heredity predisposes temperament.
18

19. Separated Twins
A number of studies compared identical twins
reared separately from birth, or close thereafter,
and found numerous similarities.
Separated Twins
Personality, Intelligence
Abilities, Attitudes
Interests, Fears
Brain Waves, Heart Rate 19

20. Limitations of Twin Studies
• Is postnatal environment equivalent?
– Non-randomness of adoptive families
• Is prenatal environment equivalent?
– Solution: Assisted Reproductive
Technology
• Mechanism?
20

21. Evolutionary Psychology:
Understanding Human Nature
Evolutionary psychology studies why we as
humans are alike. In particular, it studies the
evolution of behavior and mind using
principles of natural selection.
21

22. Topics of Evolutionary
Psychology
A number of human traits have been identified
as a result of pressures afforded by natural
selection.
Why do infants fear strangers when they become
mobile?
Why do people fear spiders and snakes and not
electricity and guns?
How are men and women alike? How and why do
men’s and women’s sexuality differ?
22

23. Natural Selection
Natural selection is an evolutionary process
through which adaptive traits are passed on to
ongoing generations because these traits help
animals survive and reproduce.
23

24. Sex Differences in Cognitive
Functions
24
Yasen et al. (in review) Neuropsychobiology.

25. Sex Differences in Cognitive
Functions
Explanation: Males = Hunters
Females = not
25

26. Human Sexuality
Gender Differences in Sexuality
Males and females, to a large extent, behave
and think similarly. Differences in sexes arise in
regards to reproductive behaviors.
Question (summarized) Male Female
Casual sex 58% 34%
Sex for affection 25% 48%
Think about sex everyday 54% 19%
26

27. Natural Selection & Mating
Preferences
Natural selection has caused males to send their
genes into the future by mating with multiple
females since males have lower costs involved.
However, females select one mature and caring
male because of the higher costs involved with
pregnancy and nursing.
27

28. 28

29. Mating Preferences
Males look for youthful appearing females in
order to pass their genes into the future. Females,
on the other hand, look for maturity, dominance,
affluence and boldness in males.
Data based on 37 cultures. 29

30. Critiquing the Evolutionary
Perspective
Evolutionary psychologists take a behavior and work
backward to explain it in terms of natural selection.
Evolutionary psychology proposes genetic determinism
and undercuts morality in establishing society.
30

31. Summary
• Genetics Primer
• Behavioral Genetics Methods
– Selective Breeding
– Pedigree Analysis
– Twins (& Adopted Twins!)
• Evolutionary Psychology
31

32. Video: Genetics versus
Environment in Dogs
• Behavioral Genetics: Dogs Decoded: Nova,
30:00 to 34:30
32