1. PowerPoint® Presentation by Jim Foley
Chapter 4
Nature, Nurture, and Human Diversity
PowerPoint® Presentation
by Jim Foley
© 2013 Worth Publishers

2. 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
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.

3. 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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Chromosome: threadlike structure made largely of DNA molecules
DNA: a spiraling, complex molecule containing genes
DNA
(Deoxyribonucleic Acid)

4. 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.
The genome: an organism’s entire collection of genes

5. How Genes Work
Genes are not blueprints; they are molecules that 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, gene expression, 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.

6. 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
Click to reveal sidebar.
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

7. 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.
Click to reveal sidebar.
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.]

8. Studies of Identical Twins Raised Apart
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?
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
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.
Click to reveal bullets, then more in sidebar.
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.

9. Searching for Parenting Effects: Biological vs. Adoptive Relatives
Despite the strong impact of genetics on personality, parenting has an influence on:
religious beliefs
values
manners
attitudes
politics
habits
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10. 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”
Click to reveal bullets.
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.

11. Nature and nurture working together Interaction of Genes and Environment
Example of self-regulation in animals: shortened daylight triggers animals to change fur color or to hibernate
Self-regulation: genes turn each other on and off in response to environmental conditions
Epigenetics: the environment acts on the surface of genes to alter their activity
Example of self-regulation in humans:
obesity in adults can turn off weight regulation genes in offspring
Click to reveal bullets and examples.
The main mechanism for epigenetic change is the methyl molecule on DNA which essential deactivates it, keeping the gene from coding proteins.
Sample of some of the citations on the obesity result at the bottom:
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.
Genetic traits influence the social environment, which in turn affects behavior.

12. Evolutionary Psychology:
Understanding Human Nature
Some topics:
Natural selection and adaptation
Evolutionary success may help explain similarities
An evolutionary explanation of human sexuality
Evolutionary psychology is the study of how evolutionary principles help explain the origin and function of the human mind, traits, and behaviors.
Click to reveal definition of evolutionary psychology.
Evolutionary principles are used in evolutionary psychology to explain human universals and commonalities; qualities that helped ancestors survive and reproduce and spread those traits in the genes of many offspring.
The trait of being adaptable is built into the human genome.
Paradox: our genes allow us not to be tied so much to our genes!
We have minds which allow us to change our behavior in response to the environment to a greater degree than other species.
We even shape our environments to suit our nature.
Humans can adapt to a variety of climates, diets, lifestyles, and skills.
We have been talking so far about human differences; we may now seek insight in the ways in which humans are alike.

13. 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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14. Artificial Selection The Domesticated Silver Foxes
Dmitri Balyaev and Lyudmila Trut spent 40 years selecting the most gentle, friendly, and tame foxes from a fox population, and having those reproduce.
As a result, they were able to shape avoidant and aggressive creatures into social ones, just as wolves were once shaped into dogs.
Click to reveal bullets.

15. How might evolution have shaped the human species?
Example:
Why does “stranger anxiety” develop between the ages of 9 and 13 months?
Hint: in evolutionary/survival terms, humans are learning to walk at that time.
Possible explanation: infants who used their new ability to walk by walking away from family and toward a lion might not have survived to reproduce as well as those who decided to cling to parents around the time they learned to walk.
Click to reveal bullets.
Another possible example of evolutionary shaping (from the text): the instinct to dislike bitter foods (which may have been toxic to our ancestors) especially during pregnancy.
Critique of evolutionary psychology: it begins with an effect (stranger anxiety, phobias) and works backward to propose an explanation. It is almost impossible to lose when proposing an explanation in hindsight, and these explanations almost always defy the level of scientific scrutiny and verification suggested in Chapter 1.

16. Evolutionary Psychology’s Explanation of Phobias
Why do people so easily acquire a phobia of snakes?
An evolutionary psychologist would note that snakes are often poisonous…
so those who more readily learned to fear them were more likely to survive and reproduce.
Can we apply the same logic to phobias about heights? enclosed spaces? clowns?
Click to reveal bullets.
Discussion question: why are clowns such a common phobia? Hint at a possibility: there is evidence that our lineage split away from those that evolved into today’s baboons and mandrills long before our ancestry diverged from today’s chimpanzees or even gorillas and orangutans. Check out a picture of a mandrill…
Critique: note how once an evolutionary psychologist has the effect (clown phobia), almost any proposal can be suggested to explain it. This is why noted paleontologist Stephen Jay Gould (1997) called hindsight explanation nothing more than “speculation [and] guesswork in the cocktail party mode.”
Note: spiders were removed from this example because they are rarely poisonous and are far less dangerous than many other animals.

17. Male and Female Differences: Focusing on Mating Preferences
First issue: quantity (of mating)
Generally, men think more than women about sex, and men are more likely to think that casual sex is acceptable.
Why might natural selection have resulted in greater male promiscuity?
An evolutionary psychologist’s answer:
Click to reveal bullets, question and answers.
Instructor: more about other male/female differences, ones which are presumed to be more influenced by culture than genes, later in the chapter.
The information below is for your use in case you decide not to use upcoming 2-3 slides to save time:
The potential answer to this question that I hope students can figure out: males who had the trait of promiscuity are more likely to have their genes continue, even spread, in the next generation. And there is little cost to spreading extra genes.
Promiscuous women, by contrast, might have been LESS likely to have this result, because they would be less likely to have stable male partners around to help with the parenting than women who were more selective about whom they had sex with.
Men who had the trait of promiscuity were more likely to have their genes continue, and even spread, in the next generation. And there is little cost to spreading extra genes.
For women, a trait of promiscuity would not greatly increase the number of babies, and it would have greater survival costs (pregnancy, once a life-threatening condition).

18. Possible Evolutionary Strategies in Seeking Partners
Q: How would evolutionary psychology explain why males and females have different preferences for sexual partners?
Men seek women with a fuller figure… to make sure they are not too young or too old to have children? Women seek males with loyal behavior and physical/social power and resources… in order to ensure the survival of the mother’s offspring?
Click to reveal bullets.

19. Experience and Brain Development
Nature/Nurture From Genes to the Role of Environment
Experience and Brain Development
Rats living in an “enriched” environment (more social interaction and physical play) experienced a greater growth in brain size and complexity than those rats living in an “impoverished” environment.
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Many kinds of stimulation help generate brain development, even providing massage and other touch to newborns (especially those born prematurely).
To make our well-used brain pathways work better, the unused connections are “pruned” away.
This means that if certain abilities are not used, they will fade.
The process of pruning is actually more like a withering away of some connections, while other connections are being strengthened (long-term potentiation).

20. Impact of Experience/Nurture on Brain Development The Process Continues into Adulthood
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Repeated practice at a finger-tapping task begins to activate a [slightly] larger group of motor neurons.

21. Is parenting a powerful environmental influence on development?
Generally, environmental influences, including parenting, account for about 10 percent of temperament, although a much higher percentage for other features such as values.
Non-abusive “average” parents should ease off on both the blame and the credit they assume for how their kids turn out.
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The “extreme” pattern of abuse and neglect can lead to many more effects than the “abused kids who become abusive” phrase in the book. You can ask students to list the other possibilities, which may include anxiety, depression, flashbacks, compulsions, or even lead to unusual strengths in coping such as problem-solving, acceptance, determination, or ability to seek out helpful resources (a key factor in resilient survivors).
Where this percentage increases: “extreme” parenting, including severe neglect and abuse

22. Peer Influence
The degree of peer influence is hard to trace. Apparent conformity (the whole group smokes) could be a selection effect (they get together because they want to be with others who like to smoke).
Interaction with peers can teach new social skills.
Parents may try to have indirect influence by selecting a child’s peers, such as by selecting a school or neighborhood. However, ultimately, most children self-select their peers.
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23. Parents vs. Peers Battling over non-genetic influence
Peers have more influence on:
Parents have more influence on:
Education and career path Cooperation Self-discipline Responsibility Charitableness Religion Style of interaction with authority figures
Learning cooperation skills Learning the path to popularity Choice of music and other recreation Choice of clothing and other cultural choices Good and bad habits
Have students guess at these before clicking to reveal each list.

24. Culture Influences on Development
Culture and the self: individualism and collectivism
Individualist cultures value independence. They promote personal ideals, strengths, and goals, pursued in competition with others, leading to individual achievement and finding a unique identity.
Collectivist cultures value interdependence. They promote group and societal goals and duties, and blending in with group identity, with achievement attributed to mutual support.
Individualist and Collectivist Cultures Compared
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On the last domain on each list, related to attributions for behavior, you might add/clarify that people in collectivist societies are more likely to give credit to others for accomplishments, as mentioned in the text when describing interviews with successful athletes.

25. Child-rearing: Cultural Differences
People in individualist cultures might raise children to be self-reliant and independent.
People in collectivist cultures might raise children to be compliant, obedient, and integrated into webs of mutual support.
People in Asian and African cultures might raise children to be more emotionally and physically close to others than in western European cultures.
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26. Differences Between Genders
Biological:
women enter puberty earlier, live longer, and have more fat and less muscle
Gender and Aggression:
men behave more aggressively than women, and are more likely to behave in ways that harm others
this difference applies to physical aggression rather than verbal or relational aggression
Mental and Behavioral Health:
women are more likely to have depression, anxiety, or eating disorders
men are more likely to have autism, ADHD, and antisocial personality disorder
Click to reveal three bubbles.
Men murder far more people than women do; it is hard to discern whether this difference is caused by men’s ability or tendency to commit murder.

27. Gender and Social Connection: Play
When boys play, the focus tends to be on the activity.
Male play is more competitive.
Men tend to dictate how the playtime will proceed.
When women play, the focus tends to be on connection and conversation.
Female play is more social.
Girls tend to invite feedback.
Click to reveal two text boxes and a question.
The question on this slide in more detail:
Is the different style of play a result of genetic male-female differences?
Or is it a part of the culturally-influenced socialization of men in preparation for competitive roles and succeeding at activities, and the socialization of women in preparation for more social, relational roles they will play? Is it nature or nurture?
Image from the 9th edition of the text.
Are these differences due to nature or nurture?

28. Gender and Social Communication
However, men and women speak about the same number of words per day. What fills in the extra time on those longer phone calls?
Women communicate more than men:
more time with friends
more text messages
longer phone calls
Maybe…. listening?
Men and women use communication differently.
Women seek input and explore relationships.
Women speak about people and feelings.
Men state their opinions and solutions .
Men speak about things and actions.
Click to reveal all text.

29. Gender and Social Connectedness
Both men and women turn to women when they want someone to talk to, seeking the “tend and befriend” response or better listening.
In general, women change roommates more often.
Women tend to have stronger ties to friends and family.
Women are often more involved with religion.
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The second bullet point refers to the study about women changing roommates more often than men. The authors of that study suggest that this may happen because women are perhaps more determined to seek good emotional intimacy. If you bring up this study, ask the class based on their experiences as college students: “do you think there are any explanations for this result?” Do the males (or females) in class have a different way of explaining this?

30. The Biology of Gender What biologically makes us male or female?
Brain Differences
During the fourth and fifth month of pregnancy, sex hormones bathe the fetal brain.
In adulthood, women have thicker areas in a part of the frontal lobes that help with verbal fluency.
There are also differences in the amygdala, hippocampus, and ratio of cell bodies to axons.
What biologically makes us male or female?
It begins with whether our 23rd pair of chromosomes looks like XX (female) or Xy (male).
Testes develop, and at seven weeks, the testes produce a flood of testosterone.
Hormones then guide the development of external sex organs.
Click to reveal bullets and sidebar.
It is worth speculating: are the adult brain differences results caused by this biological difference in the fetus, or caused by the nurture/experience?

31. Lessons about Gender: Unusual Biological Cases
Breaking Free of Gender
Transgendered people have a sense of sexual identity that is different from their birth sex.
Transsexual people act on this sense of difference by living as a member of the opposite sex, often with hormonal and surgical interventions that support this gender reassignment.
In cases in which prenatal testosterone levels were high in females, there is an increase in “tomboyish” behavior, possibly caused by other people’s response to more masculine features. However, there is not a general pattern of gender identity change.
In cases where males had underformed or absent genitalia, attempts to raise them as females generally did not work out well.
Click to reveal bullets and sidebar.
Biological changes (problems in sexual identity development) can bend gender, but not fully change it.
Do students think that these gender identity phenomena originate in biology, culture influence, or in the mind and personal experience?
The sidebar covers material that doesn’t appear until later in the chapter, but if you’re going to use the material on the left, this slide seems to follow up well from the other gender-bending possibilities.

32. Change in Social Roles?
If current trends continue, women will soon be the majority of practitioners in some fields that were once dominated by men in the United States.
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33. Culture Influence on Gender Role Development Or is it instinct?
Social learning theory: we learn gender role behavior by imitation, and by rewards and punishments that shape our behavior
Gender schemas: the cognitive frameworks for developing concepts of “male” and “female”; these frameworks guide our observations
Gender typing: the instinct which drives some children to fit into traditional gender roles
Click to reveal bullets.
Some parents may seem mystified that even when they don’t try to shape kids toward traditional gender role behavior, it happens anyway. Does that mean it’s genetic? What may be genetic is the drive to form gender schema just as kids are driven to figure out the rest of the world, and to “play detective” in figuring out what boys and girls are supposed to do, even if parents try to present no information which differentiates gender roles. Kids find out, and then imitation does its work, along with the desire to fit in and to do behavior that gets rewarded.

34. Influences on Who You’ve Become
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35. Beyond Biopsychosocial Influences: CHOICE
Is our behavior and identity rigidly determined by our combination of nature/genes and nurture/experience?
Even if free will is an illusion, it would seem that we can make choices that override our genetic influences, that differ from cultural norms, and that do not fit our environment.
We can even choose to directly alter culture, environment, and even genes.
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Humans, perhaps uniquely, have the experience (or perhaps the delusion) of rising above the mere influence of nature and nurture.