Behavior Genetics: Predicting Individual Differences

LOQ: What are chromosomes, DNA, genes, and the human genome? How do behavior geneticists explain our individual differences?

Behavior Genetics: the study of the relative power and limits of genetic and environmental influences on behavior.

Heredity: the genetic transfer of characteristics from parents to offspring

Environment: every nongenetic influence, from prenatal nutrition to the people and things around us.

Genes: Our Codes for Life

We have around 20,00 genes that are either active (expressed) or inactive from 46 chromosomes (23 from mother’s eggs, 23 from father’s sperm) made from DNA

Human genome researchers have discovered a common sequence within human DNA

Most of our traits are from our genetics such as height which influences

• Size of face

• Vertebrae

• Leg bones

Some traits like intelligence, happiness, and aggressiveness are influenced by genes

Chromosomes: threadlike structures made of DNA molecules that contain the genes.

DNA  (Deoxyribonucleic Acid):  a complex molecule containing the genetic information that makes up the chromosomes

Genes: the biochemical units of heredity that make up the chromosomes; segments of DNA capable of synthesizing proteins.

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

Twin and Adoption Studies

LOQ: How do twin and adoption studies help us understand the effects and interactions of nature and nurture?

Identical Versus Fraternal Twins

Identical (monozygotic) twins develop from the same fertilized egg that splits

• This means they are genetically identical

  • They don’t always have the same number of copies of genes repeated in their genome

Fraternal (dizygotic) twins develop from two separate fertilized eggs

• Share the same prenatal environment but are as genetically similar as regular brother’s and sisters

Shared genes mean shared experiences

• Identical twins are more likely to be extroverts and have neuroticism (emotional instability) than frateral twins are

• Identical twins look more alike to each other than fraternal twins

Identical (Monozygotic) Twins: develop from a single fertilized egg that splits in two, creating two genetically identical organisms.

Fraternal (Dizygotic) Twins: develop from separate fertilized eggs. They are genetically no closer than ordinary brothers and sisters, but they share a prenatal environment.

Separated Twins

There have been many experiments done identical twins who where seperated at birth

• After they are seperated, they monitor the behavior of both of the twins as well as other statistics such as height, weight, etc.

Biological Versus Adoptive Relatives

Studies find that people who grow up together (except for identical twins), do not resembole each other in personality, even if they are biologically related

The normal range of environments shared by a family’s children has little discernible impact on their personalities

• Heredity shapes the personalities of other primates

Genetic Relatives: biological parents and siblings

Environmental Relatives: adoptive parents and siblings

Heritability:

LOQ: What is heritability, and how does it relate to individuals and groups?

Behavior geneticists can estimate the heritability of a trait through math

• Many personality traits are about 40% heritable

• Basic intelligence is 66% genetic

  • This doesn’t mean that 66% of you intelligence is already predisposed, it varies between people

As environments become more similar, heredity becomes the main source of differences

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

Gene-Environment Interaction

Some traits develop the same in basically every environment.

• Our shared biology allows us to become more diverse

• Our genes and experience interact together, one doesn’t have superiority

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

Molecular Behavior Genetics

LOQ: How is molecular genetics research changing our understanding of the effects of nature and nurture?

Molecular Genetics: the subfield of biology that studies the molecular structure and function of genes.

Searching For Specific Genes Influencing Behavior

Most human traits are influenced by genes

• Genes are not usually solo players

Molecular Behavior Genetics: the study of how the structure and function of genes interact with our environment to influence behavior.

Epigenetics: Triggers That Switch Genes On and Off

Our experiences create epigenetic marks

• Often naturally occurring methyl molecules attached to a part of a DNA strand

  • Marks tell if it needs to ignore any gene present in a specific DNA segmant, making the cells “turn off”

• Enviromental factors such as diet, drugs, and strees can affect the epigentic molecules that regulate gene expression

• Provides a mechanism that makes the effects of childhood, trauma, poverty, or malnutrition to last a lifetime

  • Some epigenetic changes are hereditary

Epigenetics: “above” or “in addition to” (epi) genetics; the study of environmental influences on gene expression that occur without a DNA change

Evolutionary Psychology: Understanding Human Nature

LOQ: How do evolutionary psychologists use natural selection to explain behavior tendencies?

Evolutionary Psychology: the study of the evolution of behavior and the mind, using principles of natural selection.

Natural Selection: the principle that inherited traits that better enable an organism to survive and reproduce in a particular environment will (in competition with other trait variations) most likely be passed on to succeeding generations.

Evolutionary psychologists use Charles Darwin’s principle of natural selection to understand the causes of behavior and mental process such as

• Organisms’ varied offspring compete for survival.

• Certain biological and behavioral variations increase organisms’ reproductive and survival chances in their particular environment.

• Offspring that survive are more likely to pass their genes to ensuing generations.

• Over time, population characteristics may change

Natural Selection and Adaptation

Mutations passed down through natural selection allows advantageous mutations to carry on through offspring

Mutation: a random error in gene replication that leads to a change.

Evolutionary Success Helps Explain Similarities

Our Genetic Legacy

Over many generations, genes to people who do not mate tend to be lost from the human gene pool

• We all share a “universal moral grammar” despite cultural differences

• We are genetically predisposed to behave and act in ways theat our ancestors promoted to survive and reproduce

  • Now we are biologically prepared for a world that has been gone for thousands of years

Evolutionary Psychology Today

Darwin’s theory of evolution has become a base of principles in biology

• On the Origin of Speiceis, Darwin excepted this and opened neww fields for more important researchesPsychology was based on a new foundation

An Evolutionary Explanation of Human Sexuality

Male-Female Differences in Sexuality

In a BBC study from over 200,000 people over 53 countries, the men agree that “I have a stronger sex drive”

• Many men are more likely than women to initiate sexual activity.

  • This is the largest sexuality difference between males and females

Heterosexual men are alert for women’s intrests

• Often to misprecive friendliness as a sexual comeone

Men belieed their partners exoressed more sexual intrest then they reported

Many gender similarities and differences transcend sexual orientation.

Natural Selection and Mating Preferences

Women tend to be more particular at choosing a partner than men are

• Women pair wisely

• They have more at risk then men do

  • The only way she can spread her genes is by coneciving and going through pregnancy's and keeping her child alive

Men pair widely

• Traits such as smooth skin, youthful shape, cross place and time, and conveying health and fertility

• This is why teen boys tend to like women several years older than them, middle age men prefer women their own age, and older men perfer younger women

Nature selects behaviors that increase genetic success

Crituiding the Evolutionary Prespective

LOQ: What are the key criticisms of evolutionary explanations of human sexuality, and how do evolutionary psychologists respond?

Most psychologists agree that natural selection prepares us for survival and reproduction.

• Evolutionary psychologists start with an effect and work backward to explain what happened.

• They also believe that most of who we are is not hardwired

  • They do beilve that some traits and behaviors, such as suicide, are hard to explain in terms of natural selection

An evolutionary explanation of sexuality would predict that women would be choosier than men in selecting their sexual partners.

critics believe that social learning theory offers a better and instant explination of these results

• We all learn social scripts from our culture

  • Watching and imitating others in their culture, women may learn that sexual encounters with strangers can be dangerous, and that casual sex may not offer much sexual pleasure

Social Script: a culturally modeled guide for how to act in various situations.

Culture, Gender, and Other Environmental Influences

How Does Experience Influence Development?

• Our genes, when expressed in specific environments, influence our developmental differences

• We are formed by nature and nurture

Experience and Brain Development

LOQ: How do early experiences modify the brain?

Creating neural connections prepare our brain for thought, language, and other later experiences

Nature and nurture interact to sculpt our synapses.

• Experience activates and strengthens some neural pathways while others weaken from disuse.

• Nurture and nature is the biological reality of early childhood learning

  • Without that early visual stimulation, the brain cells normally assigned to vision will die or be diverted to other uses.

    • Use it or lose it

• Our neural tissue is always changing and reorganizing in response to new experiences

How Much Credit or Blame Do Parents Deserve?

LOQ: In what ways do parents and peers shape children’s development?

Parenting wields its largest effects at the extremes:

• abused children who become abusive

• the deeply loved but firmly handled who become self-confident and socially competent

Family environment also appears in the remarkable academic and vocational successes

• Shared environmental influences from the womb onward typically account for less than 10 percent of children’s differences

Peer Influence

We seek to fit in with our groups

• Preschoolers who disdain a certain food often will eat that food if put at a table with a group of children who like it.

• Children who hear English spoken with one accent at home and another in the neighborhood and at school will invariably adopt the accent of their peers, not their parents.

• Teens who start smoking typically have friends who model smoking

Cultural Influences

LOQ: How does culture affect our behavior?

Culture: the enduring behaviors, ideas, attitudes, values, and traditions shared by a group of people and transmitted from one generation to the next.

Humans enjoy the preservation of innovation

• Beneath differences is our great similarity —our capacity for culture.

• Culture transmits the customs and beliefs that enable us to communicate, to exchange money for things, to play, to eat, and to drive with agreed-upon rules and without crashing into one another

Variation Across Cultures

We see our adaptability in cultural variations among our beliefs and our values

• Humans in varied cultures nevertheless share some basic moral ideas

• Each cultural group also evolves its own norms

Norm: an understood rule for accepted and expected behavior. Norms prescribe “proper” behavior.

Variation Over Time

Cultures vary and compete for resources

• This causes them to evolve over time

• Some changes are not positive

Culture and the Self

LOQ: How do individualist and collectivist cultures differ in their values and goals?

Individualists do have a human need to belong. They join groups. But they are less focused on group harmony and doing their duty to the group

• Move in and out of groups easier

Collectovists  might experience a greater loss of identity

• Cut off from family, groups, and loyal friends

  • This causes you to lose your connections that defined you

    • Group identifications provide a sense of belonging, a set of values, and an assurance of security

Individualism: giving priority to one’s own goals over group goals and defining one’s identity in terms of personal attributes rather than group identifications.

Collectivism: giving priority to the goals of one’s group (often one’s extended family or work group) and defining one’s identity accordingly.

Culture and Child Raising

Child-raising practices are based on both individual values and cultural values that vary across time and place

Developmental Similarities Across Groups

We often fail to notice the similarities predisposed by our shared biology

• smaller than expected nation-to-nation differences in personality traits, such as conscientiousness and extraversion

• differences within a culture, such as those sometimes attributed to race, are often easily explained by an interaction between our biology and our culture

• we are subject to the same psychological forces even if we look different

Gender Development:

LOQ: How does the meaning of gender differ from the meaning of sex?

We share an irresistible urge to organize our worlds into simple categories.

• Most people’s biological traits help define their assigned gender

• Body defines your sex. Mind defines your gender

Sex: in psychology, the biologically influenced characteristics by which people define male and female.

Gender:  in psychology, the socially influenced characteristics by which people define boy, girl, man, and woman.

Similarities and Differences

LOQ: What are some ways in which males and females tend to be alike and to differ?

Males and females do differ

• Ex. girls enter puberty about a year earlier than the average boy, live about 5 years longer, expresses emotions more freely, can detect fainter odors, receives offers of help more often, and can become sexually re-aroused sooner after orgasm, twice the risk of developing depression and anxiety, and 10 times the risk of developing an eating disorder

• Ex. Men are 4 times more likely to die by suicide or to develop an alcohol use disorder, more likely to develop autism spectrum disorder, color-deficient vision, and attention-deficit/hyperactivity disorder (ADHD), and is more at risk for antisocial personality disorder

Aggression

Common examples of aggressive people are typically men since they admit more to aggression

• More willing to blast people with what they believed was intense and prolonged noise

Aggression: any physical or verbal behavior intended to harm someone physically or emotionally.

Relational Aggression: an act of aggression (physical or verbal) intended to harm a person’s relationship or social standing.

Social Power

People have perceived gender differences in power

• Tend to see men as stronger than women

Social Connectedness

We all have a need to belong,

• Males tend to be independent

  • More likely than women to hazard answers than to admit they don’t know

  • Phenomenon known as male answer syndrome

• females tend to be more interdependent

  • usually play in small groups as children

  • compete less and imitate social relationships more

  • Teens spend more time with friends

  • spend more time on social networking sites as young adults

  • Girls’ and women’s friendships are more intimate, with more conversation that explores relationships

  • Brain scans suggest that a woman’s brain, is wired in a way that enables social relationships more then men’s

The Nature of Gender: Our Biological Sex

LOQ: How do sex hormones influence prenatal and adolescent sexual development, and what is an intersex condition?

Biology does not dictate gender, but in two ways, biology influences gender:

• Genetically—males and females have differing sex chromosomes.

• Physiologically—males and females have differing concentrations of sex hormones, which trigger other anatomical differences.

Prenatal Sexual Development

Seven weeks after conception, a single gene on the Y chromosome throws a master switch, which triggers the testes to develop and to produce testosterone, the main androgen (male hormone)

• fourth and fifth prenatal months, sex hormones bathe the fetal brain and influence its wiring.

  • If females are prenatally exposed to unusually high levels of male hormones, they tend to grow up with more male-typical activity interests

X Chromosome: the sex chromosome found in both males and females. Females typically have two X chromosomes; males typically have one. An X chromosome from each parent produces a female child.

Y Chromosome: the sex chromosome typically found only in males. When paired with an X chromosome from the mother, it produces a male child.

Testosterone: the most important male sex hormone. Both males and females have it, but the additional testosterone in males stimulates the growth of the male sex organs during the fetal period, and the development of the male sex characteristics during puberty.

Adolescent Sexual Development

Hormones trigger a period of dramatic physical change during adolescence, when boys and girls enter puberty.

• Girls tend to start puberty sooner than boys

  • the landmark is the first menstrual period, menarche

    • Stressesd such as father absence, sexual abuse, insecure attachments, or a history of a mother’s smoking during pregnancy are linked to earlier menstration

• Boys, puberty’s landmark is the first ejaculation, which often occurs first during sleep (as a “wet dream”). This event, called spermarche

Puberty:  the period of sexual maturation, when a person becomes capable of reproducing.

Primary Sex: characteristics the body structures (ovaries, testes, and external genitalia) that make sexual reproduction possible.

Secondary Sex: characteristics nonreproductive sexual traits, such as female breasts and hips, male voice quality, and body hair

Spermarche: the first ejaculation.

Menarche: the first menstrual period

Sexual Development Variations

Nature may blur the biological line between males and females

• Intersex individuals may be born with unusual combinations of male and female chromosomes, hormones, and anatomy.

  • Ex. a genetic male may be born with normal male hormones and testes but no penis or a very small one

  • may struggle with their gender identity

Sex-related genes and physiology “result in behavioral and cognitive differences between males and females.”

• Nature and nurture work together.

The Nurture of Gender: Our Culture and Experiences

LOQ: How do gender roles and gender identity differ?

Gender Roles

Cultures shape our behaviors by defining how we ought to behave in a particular social role

• Shapes the gender roles

• gender roles worldwide have undergone massive changes over time

  • Ex. voting rights, job choices, martial status, and demloyment in the military

• Nomadic societies of food-gathering people have had little division of labor by sex

  • Boys and girls receive much the same upbringing. In agricultural societies

    • women typically work in the nearby fields

    • men roam while herding livestock

  • cultures have shaped children to assume more distinct gender roles

Role: a set of expectations (norms) about a social position, defining how those in the position ought to behave.

Gender Role: a set of expected behaviors, attitudes, and traits for males or for females.

How Do We Learn Gender?

Our gender identity is our personal sense of being male, female, or, occasionally, some combination of the two

• others seem to prefer androgyny

  • tend to be more resilient and self-accepting, and they experience less depression

• The social learning theory thinks we acquire our identity in childhood, by observing and imitating others and being rewarded or punished in cetain ways

  • “Tatiana, you’re such a good mommy to your dolls”

  • “Big boys don’t cry, Armand”

  • Parents help to transmit their culture’s views on gender

  • children may drift toward what feels right to them despite cultural standards

• Some people think there’s more to gender identity than imitating parents and being repeatedly rewarded for certain response

• Our gender schemas organize our experiences of male-female characteristics

  • help us think about our gender identity

• a transgender person, gender identity differs from the behaviors or

• transgender children typically view themselves in terms of their expressed gender rather than their birth designated sex

  • gender identity differs from the behaviors or traits considered typical for that person’s birth-designated sex

  • may attempt to align their outward appearance and everyday lives with their internal gender identity.

Social Learning Theory: the theory that we learn social behavior by observing and imitating and by being rewarded or punished.

Gender Typing: the acquisition of a traditional masculine or feminine role.

Androgyny: displaying both traditional masculine and feminine psychological characteristics.

Transgender: an umbrella term describing people whose gender identity or expression differs from that associated with their birth-designated sex.

Reflections on Nature, Nurture, and Their Interaction

LOQ: How do nature, nurture, and our own choices influence gender roles?

Our experiences shape us

• families and peer relationships teach us how to think and act

• Differences initiated by our nature may be amplified by our nurture

• In many modern cultures, gender roles are merging