Behavior genetics predicting individual differences
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Behavior Genetics: Predicting Individual Differences. Introduction. Behavior genetics Relative importance of heredity and environment on behavior. Genes: Our Codes for Life. Chromosomes (46 – 23 from each parent) DNA (deoxyribonucleic acid) Genes (30,000) Active (expressed)

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  • Behavior genetics

    • Relative importance of heredity and environment on behavior

Genes our codes for life
Genes: Our Codes for Life

  • Chromosomes

    • (46 – 23 from each parent)

  • DNA (deoxyribonucleic acid)

  • Genes(30,000)

    • Active (expressed)

      vs. inactive

    • Self-regulating

  • Genome

    • Complete instructions

    • Variations at gene site define

    • each person’s uniqueness

Genes: Their Location and Composition

In the nucleus of every cell we have 46 chromosomes…

Chromosome breakdown
Chromosome Breakdown





Genetic similarities
Genetic Similarities

Mr. C is




Genetic revolution
Genetic Revolution

  • Questions to discuss:

    • If it were possible, would you want to take a genetic tests telling you which diseases you are likely to suffer from later in life?

    • When you are married, suppose you or your partner are pregnant. Would you want to take a genetic test telling you which diseases your child is likely to suffer from later in life?

    • Do you think it should be legal for employers to use genetic tests in deciding whom to hire?

Twin and adoption studies identical versus fraternal twins
Twin and Adoption StudiesIdentical Versus Fraternal Twins

  • Identical twins

  • Fraternal twins

Twin and adoption studies identical versus fraternal twins1
Twin and Adoption StudiesIdentical Versus Fraternal Twins

Twin and adoption studies identical versus fraternal twins monozygotic dizygotic
Twin and Adoption StudiesIdentical Versus Fraternal TwinsMonozygotic Dizygotic

Twin and Adoption StudiesIdentical Versus Fraternal TwinsMonozygotic Dizygotic

Twin and Adoption StudiesIdentical Versus Fraternal TwinsMonozygotic Dizygotic

Twin and Adoption StudiesIdentical Versus Fraternal TwinsMonozygotic Dizygotic

Twin and Adoption StudiesIdentical Versus Fraternal TwinsMonozygotic Dizygotic

Twin and adoption studies separated twins
Twin and Adoption StudiesSeparated Twins

  • How can studying twins offer insight?

    • Same genetic make-up = differences due to?

  • Twin Studies

    • Personalities, interests, fears, abilities

    • Divorce rates

  • Anecdotal evidence

    • Why must we be

      careful in making

      judgments based on

      these findings?

Twin and adoption studies biological versus adoptive relatives
Twin and Adoption StudiesBiological Versus Adoptive Relatives

  • Genetic relatives

    • Biological parents / siblings

      • How similar are you to your brother or sister in personality?

  • Environmental relatives

    • Adoptive parents / siblings

  • Usefulness for comparison?

    • Personality of adopted children more similar to biological parents

    • Attitudes, values, manners, faith, politics = more similar to adoptive parents

  • Cautions


  • “Variation among individuals attributed to genes”

  • Herit

    • possess something someone has given you

    • Inherit traits & qualities from our parents

  • Ability

    • suffix meaning “capable”

    • If passed on, capable of showing up


  • Groups Differences

    • Heritable differences DO NOT demonstrate the relative importance of genes in explaining traits

  • Nature and Nurture

    • Nature and nurture work together

    • Genes are self-regulating

Gene environment interaction
Gene-Environment Interaction

  • Genes and experience interact

    • Stressful environments + gene activation of NT’s associated with depression

    • Evocative interactions – genes can evoke certain types of reactions

The new frontier molecular genetics
The New Frontier: Molecular Genetics

  • Molecular genetics

    • Molecular behavior genetics

      • ID specific genes influencing behavior

    • Genetics and diseases

      • ID genetic risks for diseases

    • Potential Problems?

      • China – selective abortions

      • Other issues?

Natural selection and adaptation
Natural Selection and Adaptation

  • Evolutionary psychology

    • How has natural selection shaped our universal behavior tendencies?

    • Natural selection

      • Mutation

      • Adaptation

      • Fitness

Evolutionary psychology explaining universal behaviors
Evolutionary Psychology: Explaining Universal Behaviors

  • Evolutionary psychology is the science that seeks to explain why humans act the way they do.

  • Evolutionary psychology seeks to reconstruct problems that our ancestors faced in their primitive environments, and the problem-solving mechanisms they created to meet those particular challenges.

  • From these reconstructed problem-solving adaptations, the science then attempts to establish the common roots of our ancestral behavior, and how those common behavioral roots are manifested today in the scattered cultures of the planet.

  • The goal is to understand human behavior that is universally aimed at the passing of one's genes into the next generation.

Look at our behaviors
Look at our Behaviors…

Can you answer these questions using evolutionary psychology?

  • Why do infants fear strangers when they become mobile?

  • Why are most parents devoted to their children?

  • Why do we divide people into categories?

  • Why do we have more phobias about spiders and snakes than electricity and nuclear weapons?

Now, the big one?

Sexuality and the evolutionary psychologist
Sexuality and the Evolutionary Psychologist

  • Casual sex is more accepted by men.

  • When average men and women randomly ask strangers for sex tonight, 75% of men agreed, almost no women agreed.


Sperm is cheap
Sperm is Cheap

Eggs are not

Evolutionary success helps explain similarities
Evolutionary Success Helps Explain Similarities

  • Behaviors that contribute to survival are found throughout cultures

Evolutionary success helps explain similarities outdated tendencies
Evolutionary Success Helps Explain SimilaritiesOutdated Tendencies

  • Genetic traits which helped our ancestors survive may harm us today

    • Love for the taste of fats & sweets

    • Any Others?

Critiquing the evolutionary perspective
Critiquing the Evolutionary Perspective

  • Backward theorizing

  • Impact of social influence

Reflections on nature and nurture biopsychosocial approach to development
Reflections on Nature and NurtureBiopsychosocial Approach to Development

Behavior genetics
Behavior genetics

= the study of the relative power and limits of genetic and environmental influences on behavior.


= every non-genetic influence, from prenatal nutrition to the people and things around us.


= threadlike structures made of DNA molecules that contain the genes.

Dna deoxyribonucleic acid
DNA (deoxyribonucleic acid)

= a complex molecule containing the genetic information that makes up the chromosomes.


= the biochemical units of heredity that make up the chromosomes; segments of DNA capable of synthesizing a protein.


= the complete instructions for making an organism, consisting of all the genetic material in that organism’s chromosomes.

Identical twins
Identical Twins

= twins who develop from a single fertilized egg that splits in two, creating two genetically identical organisms.

Fraternal twins
Fraternal Twins

= twins who develop from separate fertilized eggs. They are genetically no closer than brothers and sisters, but they share a fetal environment.


= the proportion of variation among individuals that we can attribute to genes. The heritability of a trait may vary, depending on the range of populations and environments studied.


= the interplay that occurs when the effect of one factor (such as environment) depends on another factor (such as heredity).

Molecular genetics
Molecular Genetics

= the subfield of biology that studies the molecular structure and function of genes.

Evolutionary psychology
Evolutionary Psychology

= the study of the evolution of behavior and the mind,using principles of natural selection.

Natural selection
Natural Selection

= the principle that, among the range of inherited trait variations, those that lead to increased reproduction and survival will most likely be passed on to succeeding generations.


= the random error in gene replication that leads to a change.