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Behavior Genetics and Evolutionary PsychologyModule 5

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Behavior Genetics and Evolutionary Psychology

Behavior Genetics: Predicting Individual Differences Genes: Our Codes for Life Twin and Adoption Studies Temperament and Heredity Nature and Nurture Gene-Environment Interaction

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Behavior Genetics and Evolutionary Psychology

Evolutionary Psychology: Understanding Human Nature Natural Selection An Evolutionary Explanation of

Human Sexuality

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Behavior Genetics: Predicting Individual Differences

Behavior Geneticists study our differences and weigh the relative effects

of heredity and environment.

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Genes: Our Codes for LifeChromosomes containing DNA

(deoxyribonucleic acid) are situated in the nucleus of a cell.

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Genes: Our Codes for LifeSegments within DNA consist of genes that make proteins to determine our

development.Dominant vs. Recessive Genes:

Examples

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Genome and Phenome

GENOTYPE The genetic makeup, as

distinguished from the physical appearance, of an organism or a group of organisms.

*How ugly you are supposed to be.

PHENOTYPE The observable physical

or biochemical characteristics of an organism, as determined by both genetic makeup and environmental influences.

How ugly you actually are.

--can change your phenotype-colored hair, contacts, etc..

.

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Twin and Adoption Studies: Handout 5-1Studying the effects of heredity and

environment on two sets of twins, identical and fraternal, has come in

handy.

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Separated TwinsCritics of separated twin studies note

that such similarities can be found between strangers. Researchers point out that differences between fraternal twins

are greater than identical twins.

Bob Sacha

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MINNESOTA TWIN STUDY

Thomas Bouchard—good name to remember!

Part 1: 1979—week-long medical and psychological assessment of Identical and Fraternal twins separated in early life and reared apart.

Part 2: --10 year __________study of aging. Adult twins between ages of 24 and 66 at 1st assessment asked to return.

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Minnesota Twin Study Cont. This study showed examples of similarities. Jerry and Mark Newman (separated at birth). Shared characteristics-firefighters, same

mustache and sideburns, same glasses, One studied forestry in college-other wanted to but worked for city trimming trees instead.

One installed fire alarms-other installed sprinklers.

Both bachelors and attracted to same type of woman.

Both only drink Budweiser ETC>>>

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Separated Twins

Separated TwinsPersonality, Intelligence

Abilities, Attitudes

Interests, FearsBrain Waves, Heart

Rate

A number of studies compared identical twins reared separately from birth, or close thereafter, and found numerous

similarities.

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Minnesota Twin Study

Studies show that Identicals have 85% similarity in IQ and Fraternals-60%.

Behavior geneticists say ½ the variation for IQ is because of genetics.

Critics: Same prenatal environment Spend avg. of 5 mths together b/f

being separated Avg. of 2 years together before

second study.

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Biological Versus Adoptive Relatives

Adoption studies, as opposed to twin studies, suggest that adoptees (who may

be biologically unrelated) tend to be different from their adoptive parents and

siblings.

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Adoptive StudiesAdoptive studies strongly point to the simple fact that biologically related children turn out to be different in a

family. So investigators ask:Do siblings have differing experiences?

Do siblings, despite sharing half of their genes, have different combinations of the other half of their genes?

Ultimate question: Does parenting have an effect?

Parenting

Parenting Influences Children’s

Attitudes, Values

Manners, Beliefs

Faith, Politics

Parenting does have an effect on biologically related and unrelated

children.

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Temperament and Heredity-Handout 5-2

Temperament refers to a person’s stable emotional reactivity and intensity.

Psychologists argue that temperaments are largely inherited based on twin

studies: Identical twins express more similar temperaments, in comparison to

fraternal twins. Examples: activity, emotionality, sociability

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Nature and NurtureSome human traits are fixed, such as

having two eyes. However, most psychological traits are liable to change

with environmental experience.

Genes provide choices for the organism to change its form or traits when environmental variables change.

Therefore, genes are pliable or self-regulating.

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Gene-Environment Interaction

Genes can influence traits which affect responses, and environment can affect

gene activity.Three types:

1. Passive genotype correlation.2. Reactive genotype-environment

correlation3. Active Genotype-environment

correlationA genetic predisposition that makes a child restless and hyperactive evokes an angry

response from his parents. A stressful environment can trigger genes to manufacture

neurotransmitters leading to depression.

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Gene-Environment InteractionGenes and environment affect our traits

individually, but more important are their interactive effects.

People respond differently toRowan Atkinson (Mr. Bean) than Orlando Bloom.

Rex Features

Alessia Pierdomenico/R

euters/Corbis

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Evolutionary Psychology: Understanding Human Nature-Handout 5-3

Evolutionary psychology studies why we as humans are alike. In particular, it studies the evolution of behavior and

mind using principles of natural selection.

This approach is helpful in raising the “why of behavior” question that is so

central to the discipline of psychology.

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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.

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Artificial SelectionBiologists like Belyaev and Trut (1999)

were able to artificially rear and domesticate wild foxes, selecting them

for friendly traits.

Any trait that is favored naturally or artificiallyspreads to future generations.

L.N. Trur, Am

erican Scientist (1999) 87: 160-169

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Human TraitsA 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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Human Sexuality

Question (summarized) Male Female

Casual sex 58% 34%

Sex for affection 25% 48%

Think about sex everyday 54% 19%

Males and females, to a large extent, behave and think similarly. Differences in

sexes arise in regards to reproductive behaviors.

Gender Differences in Sexuality

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Natural Selection & Mating Preferences-Handout 5-4

Natural selection has caused males to send their genes into the future by mating with multiple females since males have lower

costs involved. THERE IS A GENETIC ARGUMENT AS TO WHY MEN ARE “PLAYERS”—just trying to

spread their genetic code.However, females select one mature and caring male because of the higher costs involved with pregnancy and nursing.

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Mating PreferencesMales 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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THE COOLIDGE EFFECT

In certain animal species, a male that has become sexually exhausted from repeated copulation with the same female will demonstrate renewed vigor if presented with a succession of new females.

This phenomenon is called the Coolidge Effect b/c of exchange b/w Pres. And Mrs. Calvin Coolidge.

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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.

Where genders are unequal, gender preferences are wide, but when they are closely equal, preferences

narrow down.

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Evolutionary Psychologists Reply

Evolutionary psychologists argue that we need to test behaviors that expound evolutionary principles.

Evolutionary psychologists remind us how we have adapted, but do not dictate how we ought to be.

Males and females are more alike than different, and if we study these differences we can establish their

causes.

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ALTRUISM

Exercise - Essay by Lewis Thomas Assignment

Is altruism a genetic predetermined factor. Or is it, in the words of Richard Dawkins. “[that] we are born selfish. If we find that human behavior is altruistic, we will be faced with something that needs explaining.”