1. General Psychology

2. Scripture
Matthew 5:9
Blessed are the peacemakers, for they will be called children of God. .
Those who strive to prevent contention, and strife, and war. Who use their influence to reconcile opposing parties, and to prevent hostilities, in families and neighborhoods. Every man may do something of this; and no man is more like God than he who does it.

3. Thanks for Everything Dad

4. Overview: Nature/Nurture/Diversity Questions
How do we explain traits that all humans may have in common?
How do we explain the origins of diversity, the source of differences in the traits:
between genders?
among cultures?
among individuals?
But first, how do we investigate these issues?
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Additional comments to make to students:
Many human behaviors and traits (covering various areas of this course) appear to be human universals, including our capacity to adapt in diverse ways.
In this chapter, we have already to some extent left the nature vs. nurture debate behind, and instead are looking to explore the relative contributions of nature AND nurture in explaining both human universals and human differences.

5. Behavior Genetics: Predicting Individual Differences
Behavior geneticists
study how heredity and environment contribute to human differences.
The topics in the text:
genes
twin and adoption studies
temperament and heredity
molecular genetics
heritability
gene/environment interaction
Let’s start by looking at GENES.
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Instructor: Behavior geneticists study how heredity and environment contribute to human differences. Following this slide is an optional slide in case you want that definition on screen. The book words it differently: “Behavior geneticists study our differences and weigh the interplay of heredity and environment.”
Using the word “predicting” here instead of “explaining” is a different standard as we assemble our evidence into theories. We hope to not only come up with descriptions that include reasons, but to understand patterns well enough that we can predict what will happen.
The focus in this section is on the tools we can use to explore the “nature” side of the equation; later we will look at cultural and other environmental influences on the brain, gender roles, and other traits and behaviors. We will wait until a later chapter to explore and possibly explain or predict individual and group differences in intelligence.

6. The Building Blocks of Heredity and Development
GENES:
The Building Blocks of Heredity and Development
Genes are parts of DNA molecules, which are found in chromosomes in the nuclei of cells.
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DNA
(Deoxyribonucleic Acid)

7. Chromosomes are made of DNA, which are made of genes.
Chromosome: threadlike structure made largely of DNA molecules
DNA:
a spiraling, complex molecule containing genes
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8. Chromosomes and Inheritance
The human genome includes 46 chromosomes in 23 sets matched sets; each chromosome has the same gene locations.
This includes the X and Y chromosomes, not a matched set in males, who are missing some genes on the Y.
A biological parent donates half his/her set of chromosomes to his/her offspring.
We received half a set of chromosomes from each biological parent.
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9. The Human Genome: 20,000 to 25,000 Genes
The genome: an organism’s entire collection of genes
Human genomes are so nearly identical that we can speak of one universal human genome.
Yet tiny genetic differences make a difference. If there is a:
.001 percent difference in genome, your DNA would not match the crime scene/you are not the baby’s father.
0.5 to 4 percent difference in genome, you may be a chimpanzee.
50 percent difference in genome, you may be a banana.
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10. How Genes Work Genes are not blueprints; they are molecules.
These molecules have the ability to direct the assembly of proteins that build the body.
This genetic protein assembly can be turned on and off by the environment, or by other genes.
Any trait we see is a result of the complex interactions of many genes and countless other molecules.
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Note: there is rarely one single gene for one trait, and tiny differences in genes can influence big differences in appearance and behavior.

11. Next step for behavior geneticists: Controlling Variables
Can we design an experiment to keep genes constant and vary the environment and see what happens?
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Answer to these questions:
Not exactly, but we can observe what has happened when those circumstances have arisen, such as in twin and adoption studies.
Or vary the genes in the same environment?

12. Fraternal and Identical Twins
Twin and Adoption Studies
To assess the impact of nature and nurture, how do we examine how genes make a difference within the same environment?
study traits of siblings vs. identical twins
see if the siblings vary more than twins
Fraternal “twins” from separate eggs are not any more genetically alike than other siblings.
Identical twin: Same sex only
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Fraternal twins are more alike than other siblings, however, in the home environment they share. They are raised at the same time in their parents’ lives, with the same number and age of siblings.
Even identical twins, though, can have biological differences, if they have separate placentas (this happens in about one out of three times) and thus get different nourishment.
Fraternal twin: Same or opposite sex

13. Identical vs. Fraternal Twins
Twin and Adoption Studies
How do we find out how the same genes express themselves in different environments?
We can study the traits of identical twins as they grow up, or if they were raised separately (e.g., the Minnesota Twin Family Study).
Studies of twins in adulthood show that identical twins are more alike than fraternal twins in:
personality traits such as extraversion (sociability) and neuroticism (emotional instability).
behaviors/outcomes such as the rate of divorce.
abilities such as overall Intelligence test scores.
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Instructor: In these and related studies, not only are identical twins more alike than fraternal twins, but fraternal twins are more alike than random strangers even though random strangers are also raised in different environments.
Question for the students, in this slide and the next: which factor is being controlled here, and which factor is varying? [Answer: presumably, these studies are done on twins raised at first together, then having some adult time apart; if fraternal twins have more differences than identical twins, the only factor which has varied is the level of genetic similarity.]

14. Studies of Identical Twins Raised Apart
Critiques of Twin Studies
In the more recent years of the Minnesota Twin Family Study, twins have known about each other and may influence each other to be more similar.
Coincidences happen; some randomly chosen pairs of people will have similar traits, including even spouses, children, and dogs with identical names.
Environments may be similar; adoptive families tend to be more similar than randomly selected families in education, income, and values.
Similarities found in identical twins despite being raised in different homes:
personality, styles of thinking and relating
abilities/intelligence test scores
attitudes
interests, tastes
specific fears
brain waves, heart rate
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Instructor: There are cases in which identical twins are separated at birth through adoption but are later found to be twins. The Minnesota Twin Family Study is the biggest example of this.
Again, I suggest asking the students: which factor is being controlled here, and which factor is varying?
Sidebar: Another critique is that the environments or “nurture” may be more similar for twins than for a pair of unrelated people because they look identical and thus are treated more similarly.
BUT none of these factors explains, better than the genetic explanation, why fraternal twins have more differences than identical twins.

15. Searching for Parenting Effects: Biological vs. Adoptive Relatives
Studies have been performed with adopted children for whom the biological relatives are known. Findings: Adopted children seem to be more similar to their genetic relatives than their environmental/nurture relatives.
Given the evidence of genetic impact on how a person turns out, does parenting/nurture make any difference?
Does the home environment have any impact?
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16. Parenting Does Matter religious beliefs values manners attitudes
Despite the strong impact of genetics on personality, parenting has an influence on:
religious beliefs
values
manners
attitudes
politics
habits
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17. If parenting has an influence, why are siblings so different?
Siblings only share half their genes.
Genetic differences become amplified as people react to them differently.
Siblings are raised in slightly different families; the youngest has more older siblings and has older (wiser? more tired?) parents.
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18. Temperament is another difference not caused by parenting.
From infancy into adulthood, most people do not seem to change temperament (defined as a person’s general level and style of emotional reactivity).
According to some researchers, three general types of temperament appear in infancy:
“easy”
“difficult”
“slow to warm up”
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Biological explanations: anxious, inhibited infants have fast and variable heart rates and a reactive nervous system
Experience matters too. Supportive parenting can reduce the impact of early withdrawal, and unsupportive parenting or trauma can bring out the anxious, inhibited personality in a child who is predisposed to this temperament.

19. Molecular Genetics
Molecular genetics is the study of the molecular structure and function of genes.
Molecular genetics might help us see exactly how specific genes have an influence on behavior.
Genetic tests can reveal which people are at risk for many physical diseases, and may soon identify people at risk of mental health disorders.
Ethical conundrum: should people use genetic tests to select sperm, eggs, and even embryos?
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20. Clarifying Heritability
If five unrelated people had nearly identical upbringing, but differed in a trait such as shyness, then the heritability of this trait for them is close to 100 percent.
Nurture may have influenced how shy they are, but because it influenced them all in the same way, any differences are almost certainly caused by genes.
When you see a variation of some trait within a population, the heritability of that trait is the amount of variation in the population that is explained by genetic factors.
This DOES NOT tell us the proportion that genes contribute to the trait for any one person.
The heritability of a trait also does not tell us whether genetics explain differences between groups/populations.
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Height is 90 percent heritable in general. However, as a group, people are taller in this century than last, or in South Korea compared to North Korea. This is probably not caused by genetics but by nurture (nutrition).
Sidebar: This explanation is also presented in the slides for the chapter on intelligence. You may want to delete it in one of the two places.

21. How does the interaction of genes and environment work?
Nature and nurture working together Interaction of Genes and Environment
Some traits, such as the overall design of our bodies, are set by genes.
Other traits, such as physical and mental abilities, develop in response to experience.
How does the interaction of genes and environment work?
Genetic traits influence the social environment, which in turn affects behavior.
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Example: the levels above genes on the slide. Someone predisposed to depression may have that predisposition triggered by chronic stress or hormonal changes. These can lead to lifestyle changes which can reinforce depression, even changing activity in the brain. Some environmental influences can turn genes on and off.
The chart, summarizing the mutual influences among genes, brain, behavior, and environment, is from at least one article by Gilbert Gottlieb, found at:
Gilbert Gottlieb also has written more recently about epigenesis.

22. Natural Selection: How it Works
Evolutionary Psychology:
Natural Selection: How it Works
Begin with a species’ genome, which contains a variety of versions of genes that shape traits.
Conditions make it difficult for individuals with some traits (some versions of those genes) to survive long enough to reproduce.
Other individuals thus have their traits and genes “selected” to spread in the population.
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