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Chapter 4

Chapter 4 notes- genes, evolution, and behavior.docx

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Psychology 1000

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Chapter 4: Genes, Evolution, and Behavior GENETIC INFLUENCES Chromosomes and Genes Hippocrates suggested that semen contains not body parts, but some sort of design for the formation of the offspring. This idea was confirmed by Gregor Mendel, a monk whose research with garden peas in the 1860s marked the beginning of modern genetic theory. Heredity involves the passing on of specific organic factors. These factors might produce visible characteristics in the offspring, or they might simply be carried for possible transmission to another generation. Genotype: the specific genetic makeup of an individual Phenotype: the observable characteristics produced by that genetic endowment. It can be affected by other genes and by the environment. Chromosome: a tightly coiled molecule of DNA that is partly covered by protein. The DNA portion of the chromosome carries the hereditary blueprint in units is called Genes. Alleles: alternative forms of a gene that produce different characteristics.  Dominant, Recessive and Polygenic Effects o Genotype and phenotype are not identical, some genes are dominant (display of gene) and some are recessive (characteristics will not show up). o Polygenic transmission: a number of gene pairs combine their influences to create a single phenotypic trait. It magnifies the number of possible variations in a trait that can occur.  Mapping the Genetic Code o A human has a bout 25, 000 genes, the same number as a fruit fly. o 200 human genes may have arisen from genes that bacteria inserted into our early ancestors.  Genetic Engineering: The Edge of Creation o Recombinant DNA procedures: researchers use certain enzymes to cut the long threadlike molecules of DNA into pieces, combine them with DNA from another organism, and insert them into a host organism. Inside the host, the new DNA combination continues to divide and produce many copies of itself. Scientists produced human growth genome by using this procedure. o Gene knockout: to alter a specific gene in a way that prevents it from carrying out its normal function. Eg, inserting genetic amterial that will prevent neurons from responding to a particular NT and then measure whether the animal’s ability to learn or remember is affected. This helps to know the importance of particular transmitter substance in relation to the behaviors of interest. o Genetic engineering allows scientists to duplicate and alter genetic material or to repair dysfunctional genes. Behavior Genetics Techniques  Behavior geneticisits are interested in studying how hereditary and environmental factors combine to influence psychological characteristics.  Heritability coefficient: a statistical estimate of how much of the variability within a group is due to genetic factors.  Heredity: the passage of characteristics from parents to offspring by way of genes Heritability: how much of the variation in a characteristic within a population can be attributed to genetic differences  You could calculate a heritability coefficient for each group and obtain estimates for the importance of genetic factors in explaining individual differences within each group, but your results could not explain differences between groups.  If a characteristic has higher concordance (co-occurence) in people who are more highly related to one another, then this points to a possible genetic contribution (even if the people have lived in different environments)  Adoption study, a person who has adopted early in life is compared on some characteristic both with biological parents. o if the adopted person is more similar to the biological parents, then a genetic influence is suggested o if the adopted person is more similar to the adoptive parents, then environmental factors are more important  Twin studies: are one of the more powerful techniques used in behavior genetics. o Monozygotic (identical) twins develop from the same fertilized egg, so they are genetically identical. o Dizygotic (fraternal) twins develop from two fertilized eggs, so they share 50% of their genetic endowment, like siblings. o Assuming that, if the identical twins are far more similar to each other than are the fraternal twins, then a genetic factor is likely to be involved. o To test if its genetic factor or environmental factor: psychologists find and compare sets of identical and fraternal twins who were separated very early in life and raised in different environment. o Behavior genetics studies also have demonstrated that environmental factors interact with genetic endowment in important ways. GENETIC INFLUENCES ON BEHAVIOR Heredity, Environment, and Intelligence  Question: To what extent are differences in intelligence due to genetic factors, and to what extent does environment determine differences in intelligence?  Genetic argument: if intelligence is totally determined by genes: any two individuals with exactly the same genes would have identical test scores (like identical twins), but the actual data shows that test scores of identical twins are higher than any other correlations.  The more genes people have in common, the more similar they are in IQ. This strong evidence suggests that genes play a significant role in intelligence.  Environment contributes significantly to intelligence as well  Question: how do heredity and environment interact to affect intelligence? Biological Reaction Range, the Environment, Personality, and Intelligence -Reaction range: for a genetically influenced trait is the range of possibilities-the upper and lower limits- that the genetic code allows. -An individual inherits a range for potential intelligence that has upper and lower limits. -The diverse abilities measured by intelligence tests are undoubtedly influenced by large numbers of interacting genes, and different combinations seem to underlie specific abilities. -Studies of IQ gains associated with environmental enrichment and adoption programs suggest that the ranges could as large as 15-20 points on the IQ scale. -**intellectual growth depends not only on genetic endowment and environmental advantage, but also on interests, motivation, and other personal characteristics that affect how much we “apply ourselves”, or take advantage of our gifts and opportunities.  Behavior Genetics and Personality o Personality differences could be traced to differences in brain development or function-eg,. A relationship b/w neuroticism and a gene allele that increases the action of the NT serotonin, as has a relationship b/w novelty seeking and a single gene allele that decreases the action of the NT dopamine. o Five Factor Model, believe that individual differences in personality can be accounted for by variation along five broad personality dimensions or traits known as the Big Five:  Extraversion-Introversion (sociable, outgoing vs quiet, inhibited, solitary)  Agreeableness (cooperative, helpful, good-natured vs antagonistic, uncooperative, suspicious)  Conscientiousness (responsible, goal-directed, dependable vs undependable, careless, irresponsible)  Neuroticism (worrying, anxious, emotionally unstable vs, well-adjusted, secure, calm)  Openness to experience (imaginative, artistically sensitive vs, unreflective, lacking in intellectual curiosity) o Studies indicate that b/w 40-50% of the personality variations among ppl are attributable to genotype differences. Genetic factors account for a significant amt of personality difference. o Monozygotic twins are more similar to each other than are dizygotic twins. However, this issue is complicated by the possibility that identical twins may also have more similar experiences than fraternal twins. o To compare personality traits in identical and fraternal twins who either were raised together or reared apart  Allow us to divide the total variation among individuals on each personality trait into 3 components: 1) variation attributable to genetic factors 2) variation due to a shared family environment among those reared together 3) variation attributable to other factors: unique individual experiences  studies show that identical twins are far more similar in personality traits than are fraternal twins, and it makes little difference whether they were reared together or in different adoptive families. Family environment had little influence on personality differences in these studies.  The individuals’ unique experience, such as school experiences, social interactions, and individual learning experiences, was an important factor and accounted for 36-56% of the variation in individual personality traits.  Attitudes also have an inherited component.  Genes control the development and function of physical characteristics-vestibular system, the inner ear, and other structures that give us our sense of balance.  Genetic factors relevant for personality interact with the environment by predisposing an individual toward particular types of activities because of genetically influenced difference in brain activity.  Genetic influence has also been reported for a tendency to abuse alcohol, a variety of personality disorder dimensions, seasonal mood changes, anxiety and novelty seeing.  Environment and individual’s unique experiences are equally important. EVOLUTION AND BEHAVIOR No behavior by any organism can occur in the absence of biologically based mechanisms that receive input from the environment, process the information, and respond to it. In human, these inborn mechanisms allow us to learn remember, speak a language, perceive certain aspects of our environment at birth, respond with universal emotions, and bond with other humans. Evolutionary psychologists also believe that important aspects of social behavior (aggression, se roles, mate selection) are the products of evolved mechanisms (did not evolve). What evolves are genetically produced physical structures that interact with the demands of the environment to produce a behavior. Evolution of Adaptive Mechanisms Evolution  Is a change over time in the frequency with which particular genes and the characteristics they produce occur within an interbreeding population  Mutations: random events and accidents in gene reproduction during the division of cells.- they help to create variation within a population’s physical characteristics, making evolution possible  Darwin’s landmark contribution was in specifying the process by which species change over time as they adapt to environmental demands. Natural Selection  Characteristics that increase the likelihood of survival and ability to reproduce within a particular environment will be more likely to be preserved in the population and therefore will become more common in the species over time.  Natural selection acts as a set of filters, allowing certain characteristics of survivors to become more common and those of nonsurvivors to become less common/extinct.  For natural selection to work, individual variation must be present in a relevant species characteristic. Evolutionary Adaptions  Adaptions: the products of natural selection o Allow organisms to meet recurring environmental challenges to their survival, thereby increasing their reproductive ability.  Tool use, bipedal locomotion, and social organization put new selection pressures on many parts o the body. But the greatest pressure was placed on the brain structures involved in the abilities most critical to the emerging way of life: attention, memory, language, and thought.  Brain tripled in size, and the most dramatic growth occurred in the parts of the brain that are the seat of the higher mental processes.  Today’s human brain is not as big as Neanderthal’s brain. Human capabilities are not solely determined by the brain; cultural evolution is also important in the development of adaptations. Culture provides important environmental input to evolutionary mechanisms.  Domain-specific adaptations: designed to solve a particular problem, such as selecting a suitable mate, choosing safe foods to eat, voiding certain environmental hazards, detecting cheating and deception in others, and forming cooperative alliances with other ppl. This mechanisms suggest that the human mind is not a general, all-purpose problem solver but rather a collection of specialized and somewhat independent modules that
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