Behavior Genetics and Evolutionary Psychology Module 6

Behavior Genetics and Evolutionary Psychology Behavior genetics: Predicting Individual Differences Genes: our Codes for Life Twin Studies Temperament Studies Heritability Gene-Environment Interaction The New Frontier: Molecular Genetics Psychology 7e in Modules

Behavior Genetics and Evolutionary Psychology Evolutionary Psychology: Understanding Human Nature Natural Selection An Evolutionary Explanation of Human Sexuality Critiquing the Evolutionary Perspective Psychology 7e in Modules

Nature, Nurture and Human Diversity Similarities Differences Genes: Same set of chromosomes Genes: Genetic anomalies may make us different Biology: The organs and body function the same Biology: May change during development Brain: Same brain architecture Brain: Asymmetry of brain across genders Behaviors: Speak language Behavior: Speak different languages OBJECTIVE 6-1| Give examples of differences and similarities within the human family. Psychology 7e in Modules

Evolution Natural Selection The evolutionary process by which some genes in a population spread more than others do, causing species to change over time. Principles of Natural Selection: Within a species, no two are alike. Individuals differ in their suitability to their environment. Those better suited are more likely to survive and reproduce. Reproduction perpetuates the genes of better suited individuals.

Evolution Natural Selection Adaptations Advantageous physical and psychological traits that are inherited Mutations Random gene copying errors that can spark evolution by natural selection

Behavior Genetics: Predicting Individual Differences Behavior Geneticists study our differences and weigh the relative effects of heredity and environment. OBJECTIVE 6-2| Describe the type of questions that interest behavior geneticists. Psychology 7e in Modules

Genes What Genes Are and How They Work Genetic Building Blocks

Genome Genome is the set of complete instructions for making an organism Containing all the genes in that organism. Thus human genome makes us human and the genome for drosophila makes it a common house fly. Psychology 7e in Modules

Genes How Genes Affect Behavior Genotype The underlying DNA sequence that an individual inherits Phenotype An organism’s observable properties, physical and behavioral Genes contribute more directly to physical traits than to psychological characteristics.

The Nature-Nurture Debates The Pursuit of Heritability The debate over the extent to which human behavior is determined by genetics and the environment. Heritability A statistical estimate of the percentage of the variability of a trait within a group that is attributable to genetic factors.

Twin Biology To study the effects of heredity and environment two sets of twins, identical and fraternal, have come in handy. OBJECTIVE 6-4| Explain how identical and fraternal twins differ, and ways that behavior geneticists use twin studies to understand the effects of environment. Psychology 7e in Modules

Twin and Procedures Behavior geneticists study the effects of shared and unique environments on total or partial genetic makeup. Psychology 7e in Modules

Personality, Intelligence Separated Twins A number of studies have looked at identical twins raised separately from birth or close there after and have found a number of similarities. Separated Twins Personality, Intelligence Abilities, Attitudes Interests, Fears Brain Waves, Heart Rate Psychology 7e in Modules

Adoption Studies Opposed to twin studies, adoption studies suggest that adoptees (who may be biologically unrelated) tend to be different from their adoptive parents and siblings. OBJECTIVE 6-5| Cite ways that behavior geneticists use adoption studies to understand the effects of environment and heredity. Psychology 7e in Modules

Adoptive Studies Adoptive studies strongly point to the simple fact that biologically related children turn out to be different in a family. So investigators ask: Do siblings have differing experiences? Do siblings, despite sharing half of their genes, have different combinations of the other half genes? Ultimate question: Does parenting have an effect? Psychology 7e in Modules

Parenting Influences children’s Parenting does have an effect on biologically related and unrelated children. Parenting Influences children’s Attitudes, Values Manners, Beliefs Faith, Politics Psychology 7e in Modules

Temperament Studies Temperament refers to a person’s stable emotional reactivity and intensity. Identical twins express similar temperaments, suggesting heredity predisposes temperament. OBJECTIVE 6-6| Discuss how the relative stability of our temperament illustrates the influence of heredity on development. Psychology 7e in Modules

The Nature-Nurture Debates Genetic Influences Other studies of twins and adoptees show: Genetic factors account for some differences in intelligence, verbal and spatial abilities, criminality, vocational interests, and aggressiveness. There is a genetic component to psychological disorders, such as alcoholism, depression, and schizophrenia. And, there is evidence for a genetic link to people’s attitudes toward issues and activities.

The Nature-Nurture Debates Genetic Influences Heritability of Various Human Attributes The role of genetic factors is shown by the extent to which identical twins are more similar to each other than are fraternal twin pairs.

The Nature-Nurture Debates Genetic Influences Heritability of Attitudes This study involved 672 twins who rated their attitudes on various issues and activities. The results show some influence of genetic factors.

Gene-Environment Interaction Genes can influence traits which affect responses, and environment can affect gene activity. A genetic predisposition that makes a child restless and hyperactive, evokes angry responses from his parents. A stressful environment can trigger genes to manufacture neurotransmitters leading to depression. OBJECTIVE 6-8| Give and example of a genetically influenced trait that can evoke responses in others, and give another example of an environment that can trigger gene activity. Psychology 7e in Modules

Molecular Genetics: Promises and Perils Molecular geneticists are trying to identify genes that put people at risk for disorders. With this kind of knowledge parents can decide to abort pregnancies where fetuses are suspected of having such disorders But this opens up a real concern about ethical issues involving such choices. Psychology 7e in Modules

Evolutionary Psychology: Understanding Human Nature Molecular genetics studies why we as organisms are distinct. Evolutionary psychology studies why we as humans are alike. In particular it studies the evolution of behavior and mind using principles of natural selection. OBJECTIVE 6-10| Describe the areas of psychology that interests evolutionary psychologists Psychology 7e in Modules

Artificial Selection Biologists like Belyaev and Trut (1999) were able to artificially rear and domesticate wild foxes selecting them for friendly traits. L.N. Trur, American Scientist (1999) 87: 160-169 Any trait that is favored naturally or artificially spreads to future generations. Psychology 7e in Modules

Human Traits A number of human traits have been identified as a result of pressures afforded by natural selection. Why do infants fear strangers when they become mobile? Why are most parents so passionately devoted to their children? Why do people fear spiders and snakes and not electricity and guns? Psychology 7e in Modules

Question (summarized) Human Sexuality Gender Differences in Sexuality Males and females to a large extent behave and think similarly. Differences in sexes arise with regards to reproductive behaviors. Question (summarized) Male Female Casual sex 60% 35% Sex for affection 25% 48% Think about sex everyday 54% 19% OBJECTIVE 6-12| Identify gender differences in sexuality. Psychology 7e in Modules

Mating Preferences Natural selection has pressurized males to send their genes into the future by mating with multiple females because of lower cost involved. But females because of higher costs involved with pregnancy and nursing select one mature and caring male. OBJECTIVE 6-13| Describe evolutionary explanations for gender differences in sexuality. Psychology 7e in Modules

Mating Preferences In order for males to pass their genes into future they look for youthful appearance in females. Females on the other hand look for maturity, dominance, affluence and boldness in males. Data based on 37 cultures. Psychology 7e in Modules

Critiquing the Evolutionary Perspective Evolutionary psychologists take a behavior and work backward to explain it in terms of natural selection. Evolutionary psychology proposes genetic determinism and undercuts morality in establishing society. Where genders are unequal, gender preferences are wide, but closely equal, preferences narrow down. OBJECTIVE 6-14| Summarize the criticisms of evolutionary explanations of human behavior, and describe the evolutionary psychologists’ responses to those criticisms. Psychology 7e in Modules

Evolutionary Psychologists Reply Evolutionary psychologists argue that we need to test behaviors that expound evolutionary principles. Evolutionary psychologists remind us how we have adapted, but does not dictate how we ought to be. Males and females are more alike than different, if we study these differences we can establish their causes. Psychology 7e in Modules