introductory psychology: behavior genetics
DESCRIPTION
lecture 10 from a college level introduction to psychology course taught Fall 2011 by Brian J. Piper, Ph.D. ([email protected]) at Willamette University,TRANSCRIPT
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Behavioral Genetics
Brian J. Piper, Ph.D.
Goals
• Genetics Primer
• Behavioral Genetics Methods– Selective Breeding– Pedigree Analysis– Twins (& Adopted Twins!)
• Evolutionary Psychology
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Gregor Mendel
• Austrian friar who studied pea plants (29K!)
• Dichotomous traits
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1822-1884
http://www.accessexcellence.org/RC/AB/BC/Gregor_Mendel.php
Gregor Mendel
• Homozygote versus Heterozygote• Dominant versus Recessive
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1822-1884
http://www.accessexcellence.org/RC/AB/BC/Gregor_Mendel.php
Examples of Mendelian Patterns
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S = spherical, s = wrinkled
Huntington’s Disease
• Neurodegenerative Disease– Loss of motor function
– dementia
H h
h Hh hh
h Hh hh
7http://en.wikipedia.org/wiki/Huntington%27s_Disease
1 min video: http://www.youtube.com/watch?v=JzAPh2v-SCQ
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Terminology
Chromosomes containing DNA (deoxyribonucleic acid) are situated in
the nucleus of a cell.
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Genes: Our Codes for Life
Segments within DNA consist of genes that make proteins to determine our
development.
Chromosome 4: Huntingtin gene;
Pedigree
Rife (1940) collected info from 2,200 college students and their parents
Parent ChildR X R = 7.6R x L or L x L = 21.6
Rife (1940) Genetics, 25, 178-186.
Aggression
• Brunner described an extended family in which 5 males had impulsive aggression including:
– Exhibitionism– Arson– Rape
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Limitations of Pedigree
• Paternity
• Best for Dichotomous Characteristics
• Families share environments too
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Selective Breeding
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• Simple procedure with extended history
• May involve controlling environment
• Has been completed for emotions and drug preference
• Limitations:– Generalizability– Ethics
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Twin Studies
Studying the effects of heredity and environment on two sets of twins,
identical and fraternal, has come in handy.
Logic
Relationship Genetic Relationship Predicted Similarity
Monozygotic Twins 100% High
Dizygotic Twins (same sex)
50% Moderate
Siblings 25% Lower
Unrelated Minimal Modest
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Logic
Relationship Genetic Relationship Predicted Similarity
Monozygotic Twins 100% High
Dizygotic Twins (same sex)
50% Moderate
Siblings 25% Lower
Unrelated Minimal Modest
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Temperament and Heredity
Temperament refers to a person’s stable emotional reactivity and intensity.
Identical twins express similar temperaments, suggesting heredity
predisposes temperament.
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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
Limitations of Twin Studies
• Is postnatal environment equivalent?– Non-randomness of adoptive families
• Is prenatal environment equivalent?– Solution: Assisted Reproductive
Technology
• Mechanism?
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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.
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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?
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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.
Sex Differences in Cognitive Functions
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Yasen et al. (in review) Neuropsychobiology.
Sex Differences in Cognitive Functions
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Explanation: Males = Hunters Females = not
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Human Sexuality
Males and females, to a large extent, behave and think similarly. Differences in
sexes arise in regards to reproductive behaviors.
Gender Differences in Sexuality
Question (summarized) MaleFema
le
Casual sex 58% 34%
Sex for affection 25% 48%
Think about sex everyday 54% 19%
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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.
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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.
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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.
Summary
• Genetics Primer
• Behavioral Genetics Methods– Selective Breeding– Pedigree Analysis– Twins (& Adopted Twins!)
• Evolutionary Psychology
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Video: Genetics versus Environment in Dogs
• Behavioral Genetics: Dogs Decoded: Nova, 30:00 to 34:30
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