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
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
Fraternal (dizygotic) twins develop from two separate fertilized eggs
Shared genes mean shared experiences
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.
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
Genetic Relatives: biological parents and siblings
Environmental Relatives: adoptive parents and siblings
LOQ: What is heritability, and how does it relate to individuals and groups?
Behavior geneticists can estimate the heritability of a trait through math
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.
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
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
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
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
Evolutionary Psychology Today
Darwin’s theory of evolution has become a base of principles in biology
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”
Heterosexual men are alert for women’s intrests
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
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.
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
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
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:
Family environment also appears in the remarkable academic and vocational successes
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
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
Norm: an understood rule for accepted and expected behavior. Norms prescribe “proper” behavior.
Variation Over Time
Cultures vary and compete for resources
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
Collectovists might experience a greater loss of identity
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
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.
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
Common examples of aggressive people are typically men since they admit more to aggression
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.
People have perceived gender differences in power
We all have a need to belong,
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)
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
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
Sex-related genes and physiology “result in behavioral and cognitive differences between males and females.”
The Nurture of Gender: Our Culture and Experiences
LOQ: How do gender roles and gender identity differ?
Cultures shape our behaviors by defining how we ought to behave in a particular social role
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
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
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