Introductory Psychology PSYC 1000
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Behavioral Genetics and Sociobiology Chromosomes Genes and Environment V thin the nuclei of living human cells are 23 pairs of rodlike structures called chromosomes The chromosomes contain the units of inheritance genes which in interaction with the environment guide the individual39s physical development including the development ofthe brain and nervous system Since the brain and nervous system mediate mental and behavioral processes it is reasonable to include genetics in one39s study of psychology An individual gene may be thought of as coding for the production ofone or another or no protein Genes are found within the nucleus of every cell in your body They are composed of DNA This DNA serves as the template for the production of RNA The RNA serves as the template for producing proteins from amino acids Collectively the combination ofthe proteins produced by all the genes is a living organism like you Of course there must be available in the environment certain basic ingredients for normal development ofthe organism Development is best thought of as being due to the joint operation of genes and environment 0 Different environments lead to different developments so two genetically identical zygotes fertilized eggs in two different environments would be expected to develop differently Likewise two zygotes with different genes would be expected to develop differently even ifthey were in identical environments Furthermore the environment that would lead to the quotbestquot development for an individual of one genetic constitution may not be the same as the environment that would lead to the best development for a genetically different individual This is known as Gene x Environment interaction Mitosis and Meiosis Cells in your body can reproduce themselves through a process known as mitosis Barring errors mitosis results in exact duplication ofthe DNA in the parent cell Germ cells produce eggs or sperm through a process known as meiosis While it is not important for this class for you to know all of the details of meiosis you should know the following c There is an exchange of genetic material between paired chromosomes crossingover 0 Each gamete sperm or egg receives only one of each ofthe paired chromosomes 0 Which one of the two chromosomes in each pair goes to an individual gamete is random not related to which one of the two chromosomes in any of the other 22 pairs of goes to that gamete This is known as random assortment Gray3doc Page 2 o This crossingover and random assortment produces a remarkable shuffling of the genes that go into the gametes such that it is nearly impossible that any two gametes produced by the same individual are identical Sexual Reproduction ln sexual reproduction the zygote formed by the union ofone sperm and one egg has approximately half of its DNA from its father and half from its mother The shuffling of the genes that took place during meiosis combined with the contribution of genes from two different parents produces great genetic diversity among the offspring This genetic diversity is likely to be ofgreat bene t in helping a species adapt to changing environments In that circumstance it is likely that a few ofthe new genetic combinations will be especially good at living in a new environment even if most ofthe new genetic combinations are not Now if the environment was not changing rapidly then the best strategy would be to reproduce asexually and many organisms do exactly that After all if you have put together a good combination of genes why mix them all up again Think of a good combination of genes as being like a good hand in poker An organism has a lot more that 6 genes but to keep it simple imagine that we are playing 6 card poker One parent has a very good hand a straight flush 2 3 4 5 6 7 of hearts The other parent has an equally good hand 2 3 4 5 6 7 of spades lfthey sexually reproduce each gives half of its genes cards to the offspring Who is going to have the better set of genes cards the parents or the offspring Some organisms have adopted the marvelous strategy of reproducing asexually when the environment is stable but shifting to a sexual mode of reproduction during times of great environmental change so they can nd a new combination of genes better suited to the changed environment then back to asexual reproduction once things have settled down again One example of such a creature is the hydra Point your browser to httpbiologyaboutcomlibramweeklyaa090700ahtm for more information on this It has been suggested that long ago all species reproduced by this strategy but then most of them lost that ability during a period of prolonged environmental change andor during a time when the number of individuals left in the breeding population was very small Defining Sex Biologically When biologists determine which morph of a species is male and which female it is the size of their gametes that is important The sex that produces the larger gametes eggs is female that producing the smaller gametes sperm male In humans having two alike sex chromosomes XX is associated with the female sex and two different sex chromosomes XY with the male sex This is not universally so In birds the males have two alike sex chromosomes the females two different sex chromosomes The male human typically produces more male sex hormones androgens including testosterone and less female sex hormones than does the female human There are also well known differences between the genitalia of males penis and Page 3 scrotum and females clitoris and vagina Gender identity with which ofthe two social categories quotfemalequot or quotmalequot does one identify usually but not always agrees with biological definitions of sex Simple Inheritance If you were to look at a single locus location of a gene on each member of pair of your chromosomes you might nd that the gene on the one member is identical to the gene on the other chromosome You would then be said to be homozygous at that locus However the genes that can be found at a given locus can come in different varieties alleles If you have two different alleles at a given locus then you are heterozygous at that locus The phenotype of an organism is its observable characteristics while the genotype of an organism is the particular set of genes it has inherited Most observable characteristics result from the interplay of genes at several loci and thus are polygenic but for some characteristics such as the wrinkling of Gregor Mendel s pea seeds the characteristic results from the genes at a single locus Rather than dealing with the wrinkling of pea seeds I shall discuss a simple model of the inheritance ofa blood type in humans One allele for blood type is the A allele Individuals who have one or two A genes produce a particular protein we shall just call it protein A in their blood Because it takes only one A gene for the A characteristic to be expressed in the blood the A gene is considered dominant Another allele is the 0 gene The 0 gene may be thought of as coding for the production of no extra protein in the blood Because an individual has to have two 0 genes to have the phenotype of Type 0 blood the gene 0 is recessive There is a third common allele for blood type the B gene The B gene is dominant that is it takes only one B gene for the B protein to be produced in the blood When there are two or more dominant genes available at a locus then we have codominance An individual with two different dominant genes will express the characteristics of both dominant genes Genotype 00 A0 AA Bo BB AB BloodType O A A B B AB Genetic Context and Inheritance l have grossly oversimpli ed the concept of dominance in genetic inheritance Whether a gene is dominant codominant or recessive is a function ofthe other genes which are involved in the chain of reaction that leads to a product that modifies a phenotype Even the simplest of traits are generally regulated by a long chain of processes that interact with one another in constructing the final product Each step in this chain is under the control of a gene If one of the steps is ratelimiting then the gene at that step may appear to be the only gene that in uences the phenotypical trait For example think about water owing through a series of funnels from each to the next and nally into the phenotypic basin The wider a funnel at its base the faster the water can ow through it The one funnel with the most narrow base will provide the Page 4 ratelimiting step Water cannot pass through the system any faster than it can through the slowest funnel Now think of each funnel s size as being determined by a different gene A gene that affects the size of the ratelimiting funnel will affect the phenotype but genes that affect the other funnels will not unless they reduce the size of one of the other funnels to less than that of the ratelimiting funnels In this way it appears that a single gene is affecting the phenotype but in fact the phenotypic product results from the interaction of many genes Consider the inheritance of purple color in snapdragon owers The gene that controls the ratelimiting step has two alleles one dominant and one recessive The recessive gene codes for the production ofonly a small amount ofthe biological product that is involved in making the owers purple The dominant gene codes for a large amount ofthat product A plant that has two of the recessive genes will have very little of the purpleproducing product A plant that has one recessive gene and one dominant gene will have a medium amount ofthe purpleproducing product A plant that has two dominant genes will have much of the purpleproducing product Now imagine that there is a certain amount a threshold of the purpleproducing product that must be made for there to be any effect on the phenotype A plant with less than the threshold value will be white and a plant with more than the threshold value will be purple A homozygous recessive snapdragon will not reach the threshold so it will have no purple owers just white flowers but the heterozygous plant with a single dominant gene will produce enough of the purpleproducing product to exceed the threshold and cause the plant to have purple owers Having two dominant genes is no more effective in getting across the threshold than is having just one dominant gene so the homozygous dominant plant looks just like the heterozygous plant with purple owers A more complete discussion of the effects of genetic context on inheritance can be found in the excellent article The Importance of Context in Genetics 2003 American Scientist 91 416423 Simple Inheritance of Fearfulness in Dogs John Paul Scott and John Fuller demonstrated simple inheritance of a sort of fearfulness in dogs They started with basenjis who are fearful of strange people and cocker spaniels who do not show such fear When they crossed basenjis with cockers all ofthe F1 offspring expressed such fear This is consistent with the hypothesis that such fearfulness is controlled by a genes at a single locus with the allele coding fearfulness being dominant Let us use the letter F to stand for the dominant fearful gene and fto stand forthe recessive nonfearful gene The genotype of the F1 offspring is then Ff Mother Now what should happen ifwe cross the F1 offspring Father F with one another As you can see in the diagram to the right F we would expect to get 75 fearful pups 25 not fearful f which is exactly what Scott and Fuller observed Scott and Fuller also backcrossed the F1 generation with the purebred cockers and purbred basenjis As you can see from the below tables the expectation is that the Page 5 F1 cocker matings would produce 50 fearful pups and the F1 basenji matings 100 fearful pups The expected percentages were obtained Cocker Basenji F1 f f F1 F F F F f f I should add that Scott and Fuller also found other traits in these dogs that were inherited simply and independently of the fearfulness trait Nature and Nurture Genetics and Environment Nature refers to the effects of genes nurture refers to the effects of environment Some scientists produce estimates ofthe heritability of various characteristics that is in an entire population of individuals what percentage ofthe differences between individuals on that characteristic is due to genetic differences between individuals rather than to differences in the environments to which the individuals have been exposed These estimates can be easily misinterpreted Consider the characteristic of aggressiveness in mice Suppose that I am working with inbred mice mice that are nearly genetically identical to one another Since the mice do not differ from one another genetically 100 of the observed differences in their aggressiveness must be due to environmental factors 0 to genetics Now suppose that work with outbred mice but I rearthem in highly controlled laboratory conditions so that each mouse has the same environment as all other mice In this circumstance 100 ofthe observed differences in aggressiveness must be due to genetics 0 to environment When someone gives you a heritability estimate for some characteristic do keep in mind the fact that such an estimate is speci c to a population with a particular amount ofenvironmental variance and a particular amount of genetic variance lfthe population is changed such that individuals differ from one another less in terms oftheir individual environments or more in terms of their genotypes then the heritability would increase Psychologists have often made the mistake of believing that if a trait can be modified through environmental change then it must have been initially established environmentally also For example if a behavioral disorder can be treated with environmental change such as behavior modification techniques changing response contingencies the psychologist may conclude that the disorder was caused by a bad environment the mother is often blamed Such inferences are not justified since genetically caused events can be environmentally modi ed For example PKU phenylketonuria is a disease caused by a person having a pair of recessive genes not having the normal dominant gene these persons do not produce an enzyme that is necessary properly to metabolize certain foodstuffs One consequence of their abnormal metabolism of such foodstuffs is the production of poisons that damage their brains and lead to mental retardation Despite the fact that PKU is inherited a simple environmental treatment avoiding foods that contain phenylalanine solves the problem Page 6 Habitat Selection Genetic constitution may cause an animal to select or create a particular type of environment That environment may then cause the animal to develop in a way different than it would if it were in a different environment That is genes gt habitat selection behavioral development In such a case what is causing the differences in behavior for animals who have experienced different environments At the proximal level the environment is causing the differences but at the ultimate level the differences are genetically caused since genes caused the animals to choose or create their environments Wecker 1964 Scienti c American studied two subspecies of prairie deer mice Prairie deer mice are cute little critters They have a baby face with big bulging eyes and a short bicolored tail cinnamon brown on top cream on bottom I worked with them when I lived in Ohio A similar species can be found here in North Carolina They are native American mice as opposed to the imported European house mouse I should warn you that deer mice have been identi ed as one ofthe species that carries the deadly Hanta virus i Photo of Peromyscus One breed of these mice usually lives in the forest the other in the plains If you give these mice a choice between living in a field or living in a wooded area the plains breed chooses the eld and the forest breed chooses the woods This habitat preference is not caused by early experience it is genetically caused If you raise the plains breed in the woods they still select the eld when given a choice So what if you try to explain other naturally occurring behavioral differences between these two subspecies of prairie deer mice The psychologist would be tempted to say that they act differently because they are raised in different environments and at a proximate level this may be true Being raised in the plains might well lead to different behavioral development than being raised in the woods but if it is genetics that is causing the one breed to choose to live in the plains and the other breed to choose to live in the woods isn39t genetics a higherlevel cause of the behavioral differences between the two breeds A similar confounding entanglement of genetics and environment may occur in human development Certain parenting styles tend to be associated with the development of quotcompetentquot children other styles with less desirable development recall our discussion of Diana Baumrind s research from Chapter 2 of Gray Psychologists have often used such associations to confirm their beliefthat different parenting styles providing the children with different social environments cause different development That is their explanation ofthe observed correlation is parental style child s competence An alternative explanation is tenable Children seem to be born with different temperaments and behavioral dispositions Some love contact others avoid it some fuss others are quiet etc Although the fetal environment may cause some such differences genetics likely account for most ofthem Babies who act differently Page 7 evoke different responses from their parents so the association between characteristics ofthe child and parental behavior may be as much a case of the child39s behavior affecting the parent as vice versa Maybe competent children are those who were born with the genetic constitution that disposes them towards developing into competent persons and also disposing them into acting in ways that cause their parents to adopt that parenting style associated with the development of competence This could account for the observed association between parenting style and development of competence even in the absence ofany effect of parenting style on the development of competence That is child s genes gt child s competence gt parental style Another possible exists A baby39s genetic constitution may cause it to act in ways that evoke from its parents the type of parental care that causes the child to develop a certain way That is the child39s genes cause it to selectcreate the environment make the parents act a certain way that determines the child39s subsequent development child s genes child s behavior parental style gt child s development of competence So what is causing differences in children39s competence parental care environment or genetics Inheritance of Polygenic Characteristics The strongest evidence for inheritance of behavioral dispositions comes from nonhumans upon whom we can do experiments such as selective breeding Consider a study done long ago by Tryon 1940 Yearbook of the National Society for Studies in Education 39 111119 The mazesolving quotintelligencequot of rats was measured The quotsmartestquot males were mated with the smartest females and from their offspring only the smartest mated with the smartest et cetera across six generations The most quotstupidquot males were paired with the most stupid females across six generations too The result was the creation oftwo different strains of rats one very good at solving mazes and one very poor at doing so This is quite convincing evidence that mazeintelligence in rats is heritable genetically influenced Many such studies have been done with nonhumans clearly establishing the heritability ofvarious psychological attributes The more sophisticated studies control for the effects of parental care Why do intelligent parents produce intelligent offspring Is it because they give their offspring their intelligenceenhancing genes or because they raise their offspring differently than do less intelligent parents or both One technique for separating the effects of parental care from the effects of genetics is crossfostering Using Tryon39s study as an example we take half ofthe smart parents39 offspring and foster them onto dull parents and half ofthe dull parents39 offspring and foster them onto smart parents This gives us 2 BP biological parents x 2 FP foster parents 4 combinations to evaluate smart BP amp FP smart BP dull FP dull BP smart FP and dull BP amp FP Often both genetic BP and environmental FP factors prove to be important 80 what about humans The research with humans is bound to be more complicated and dif cult to interpret since we cannot do selective breeding experiments with humans One approach is to measure the psychological similarity between Page 8 monozygotic identical twins dizygotic fraternal twins siblings and other pairs with varied degrees of genetic relatedness When psychological similarity is correlated with genetic relatedness then the trait is considered to be in uenced by genetics For example monozygotic twins are psychologically more alike one another than are dizygotic twins Such evidence is even stronger when the data include quotnatural crossfostering experimentsquot that is persons who have been adopted Again the usual result is that both genetic and environmental factors prove important Among the psychological attributes now considered to be influenced by genetics are extroversion Loehlin et al 1982 J Person Soc Psychol 42 10891099 neuroticism Scarr et al 1981 J Person Soc Psychol 41 885898 dominance and aggressiveness Goldsmith 1983 Child Development 54 331355 and intelligence Bouchard amp McGue 1981 Science 212 10551059 We shall considerthe evidence for the heritability of intelligence later in the semester when we cover Chapter 10 If you still have trouble accepting the notion that genes influence psychological characteristics ask yourself this question What would have happened if you were mistakenly exchanged with another baby at the hospital where you were born Would your parent39s fosterbaby have grown up to be exactly the same person you are now lfyou answer quotnoquot then you accept the in uence of genes Would you raised by other parents have grown up to be exactly the same person you are now Your quotnoquot to this question indicates you also accept the in uence of environment Behavior Genetics Free Will and Egalitarianism Most people have little dif culty accepting the fact that the genes they received from their parents in uence their physical characteristics such as skinhaireye color blood type type of ear lobe etc Some have difficulty however with the idea that one39s mental and behavioral dispositions are also influenced by genetics Perhaps this dif culty stems in part from our clinging to the delusion of quotfree willquot and we did not choose our genes If you accept the idea that mental and behavioral events are the product of an interaction between the brainnervous system and the environment then you should be able to deduce that mental and behavioral events are genetically in uenced since the brain and nervous system are physical structures and genes clearly affect organisms39 physical characteristics Few people would argue that the differences between human beings and other animals stem only from environmental effects A dog raised in the same environment as a human remains quite different from a human Clearly genes are important in determining differences between different species Actually the genetic differences between humans and other apes are relatively small The genetic differences between you and me are yet smaller Humans share a common genetic constitution with only relatively minor differences among us These minor differences are however associated with physical and psychological differences among us Part of our reluctance to accept the notion that genetics in part determines the differences among us may result from our egalitarianism Egalitarianism is the belief that all persons should have equal political and social rights a belief to which I very strongly subscribe Egalitarianism does not however require that all humans be identical Page 9 on all characteristics You and I can differ on various attributes but still be granted equal rights can39t we Another part of our fear of genetic explanations of human differences may stem from past and present abuses of genetic explanations by racists To the best of my knowledge there is no evidence that the genes that determine skincolor have any direct effect on psychological attributes Such genes may of course interact with the environment in a racist society leading to psychological differences For example suppose that people with blue skin are the subject of unfair discrimination not being given the same political economic and social rights that others are given Such unequal treatment would likely lead to psychological differences between blue people and others thus producing an association between blueness and psychological characteristics By the way there actually are blue humans They are blue almost purple because they lack a hormone that converts a blue type of hemoglobin methemoglobin into normal red hemoglobin Curiously injection ofa blue dye methylene blue will turn these people pink by converting the blue hemoglobin into normal hemoglobin The condition is not associated with ill health This congenital abnormality appears to be inherited via a recessive gene or genes As would be expected for a rare condition due to recessive genes its occurrence is associated with inbreeding Cathy Trost s article in the November issue of Science 85 p 35 39 is an interesting and very readable story about Benjamin Stacy who descended from a Martin Fugate a blue Frenchman who settled on the banks of Troublesome Creek in Eastern Kentucky in 1820 Martin Fugate married a woman who carried the recessive gene Four of their seven children were blue The Fugates intermarried for many years in this isolated mountainous part of Eastern Kentucky and the number of blue people grew and grew Once coal mining and the railroads brought the outside world to this isolated community the Fugates started marrying outside oftheir clan and the frequency of blue people dropped Ben Stacy is one of the last know blue Fugates Although very blue at birth now he is a relatively normal color except that his lips and fingernails turn purple when he is cold or angry For reasons unknown to me some persons with this condition retain their baby blueness as they grow up while others nearly loose it i The Blue Peo le of Troublesome Creek The Science82 article with background music You will also find there a link to a message posted by Ben Stacy in March of 1999 He reported that he was currently a student at Eastern Kentucky University The Blue Peo le of Troublesome Creek PowerPoint show that includes a scanned image ofan artist s rendition of Martin Fugate and his family Page 10 Genetic Engineering One ofthe most remarkably new genetic technologies developed late in the 20th century involves the ability to move genes from one species to another In 1985 Monsato transfered a human gene into petunia plants Science 85 April p 76 The transferred gene made these plants produce a human hormone Such research clearly has the prospect of providing a way to produce human hormones for medical treatment In 1986 researchers at the University of California at San Diego transferred firefly genes into tobacco plants and monkey cells To see a picture ofone ofthe resultin glow in the dark tobacco plants just point your web browser to Glow in the Dark Tobacco In 1993 researchers at the Albert Einstein College of Medicine inserted refly genes into tissue samples taken from patients with tuberculosis Time May 17 1993 p 25 Within 2 hours the TB bacteria start glowing These tissue samples can then be treated with different antibiotics to see which antibiotic can successfully be used to treat the patient An effective antibiotic stops the glowing ofthe bacteria This greatly reduced the time needed to determine which antibiotic is the one to use Glow in the Dark Pigs Genetic Testing Genetic tests are available to determine whether or not one carries the genes associated with several diseases and I expect the number of diseaseassociated genes which can be detected will increase greatly in the near future One ofthe potential problems associated with such testing is that the results of such a test can be used against the person tested For example an employer could require such tests as a condition of employment and then refuse to hire a people whose genes indicated they were likely to develop one or another disease Ifsuch information were made available to others such people might nd themselves unemployable and uninsurable One example of the sort of potential abuse was discussed in Time in 1994 January 167 page 53 An HMO in California learned that a genetic test had revealed that the baby being carried in the womb of one it its clients had the gene associated with cystic fibrosis The HMO advised the client that they would pay for an abortion but that if she allowed the baby to be born the HMO would not pay for any treatments for the baby That is pretty scary Page 11 Assessing the Chromosomes in Sperm Sometimes a man will want to have the chromosomes in his sperm evaluated to see if his sperm have chromosomal damage from exposure to environmental pollutants for example Apparently the sperm s chromosomes cannot be evaluated until after they have joined with an egg but then it is dif cult to determine which chromosomes are from the sperm and which from the egg Researchers at the University of Hawaii hit upon a remarkable way to solve this problem They take hamster eggs strip them oftheir protective outer coating and then fertilize them with human sperm Science 81 p 22 25 In such a hamsterhuman zygote it is easy to tell the human sperm s chromosomes from the hamster egg s chromosomes Physiological Psychology and Proximate Causation of Behavior When attempting to explain a behavior one usually looks somewhat myopically backwards in time to nd potential causal events that occurred shortly before the behavior of interest For example suppose one asks why it is that unlike other primates human females do not have a distinct period of sexual heat The physiological psychologist would look for what hormonal and neural events precede sexual heat in nonhuman primates and would then tentatively label these as the causes of sexual heat She might then experimentally manipulate these putative causal events to see if she can control the occurrence of sexual heat in nonhuman primates if she can then she is more certain that she has found the cause She might then look for the same hormonal and neural events in human females and if she did not nd them then she would say that the absence of such events in women is the cause oftheir not having a distinct period of sexual heat Because the cause is so close in time to the behavior of interest we call causal investigations like this one investigations of proximate causation Natural Selection and Ultimate Causation of Behavior Earlier we discussed the English naturalist Charles Danrvin who argued that the bodily and behavioral characteristics of plants and animals change across generations through a process of natural selection Characteristics which promote the survival and reproductive success ofan organism become more frequent across generations We now know that it is the frequency of genes which is altered by natural selection Genes which are associated with characteristics that make the individual better at reproducing will be propagated better than will be genes associated with lower levels of reproductive success Such genes are said to be high in reproductive fitness Some scientists sociobiologists and evolutionary psychologists attempt to look far back in time to nd how natural selection might have caused certain behaviors to become very common in a species Such a search is an attempt to nd ultimate causation Later this semester I shall discuss a few potential ultimate causes ofthe absence of sexual heat in women but for now let me tackle a much easier problem Why is it that most people are interested in taking care of their children Not to assure quotsurvival ofthe speciesquot a long debunked but still common myth but because Page 12 genes that make one appropriately care for their children are much more reproductiver t good at reproducing themselves than are genes that make one an uncaring parent Imagine that we start a new species in which a single gene pair determines whether or not a particular type of parental care is likely to be show by the reproductive individual There are two forms of the gene P for parental a new gene that arose from mutation and N for nonparental The P gene disposes one to provide the parental care the N gene disposes not to Suppose we start out with 1 P genes and 99 N genes in the entire population Individuals with P genes will take better care of their children than will those with N genes Accordingly children with P genes from their parents will be more likely to survive and subsequently reproduce themselves Having the P gene rather than the N genes confers a reproductive advantage and each generation the frequency of the P genes in the population increases while the frequency of the N genes declines Eventually all or nearly all ofthe members ofthe population will have P genes and will exhibit the parental care Of course taking care of the children is not the only important determinant of successful reproduction One must be smart enough andor strong enough to survive to sexual maturity and to attract a mate so there will be selective pressures favoring attributes that are associated with survival and attracting mates Not all species invest as heavily in parental care as do humans Zoologists sometimes speak of two different reproductive strategies here rselection and K selection Rselection refers to the strategy of putting all reproductive effort into making lots of offspring and little into caring for them If an animal makes 1000 babies at a time it doesn39t matter much if 95 ofthem die it still has successfully reproduced This strategy seems to work well in small shortlived species like mosquitoes where premature death such as a mosquito larva being eaten by a hungry sh is pretty much a chance factor that is unaffected by how well the parents raised the offspring Kselection refers to the strategy of making only a few offspring but then heavily investing in them caring for them well to assure that they survive Adaptation by Natural Selection Organisms39 environments sometimes change in ways that change the relative reproductive tness ofdifferent genes and this may provide the species a way to adapt across generations to the environmental change For example there is a species of moth in England which before the industrial revolution was almost always light colored This moth tended to rest against light colored surfaces so being light colored helped hide it from predators There was a little genetic variability with respect to color dark colored moths were sometimes seen but not often as they were too easily seen by predators During the industrial revolution soot from burning coal coated almost everything in England This resulted in a change in the relative reproductive tness of light versus dark moths in England shifting the advantage to the dark moths who did not stand out when resting on sooty surfaces Accordingly the dark moths were better at surviving to reproduce and soon almost all moths ofthis species were dark Now that the English have cleaned up their air the lightcolored morph of these moths is once again most common Page is The Case of industriai Meiamsm r inciudes photos of the moths e ay page 68 giyes anotner ekarnpie of adaptation by naturai seiection Finches in the G apagos naye igger bodies and stronger beaks duringyears of guickiy tnattne big guys Coadapted Gene Complexes Positive Assortment and Reproductive Isolation Suppose tnat our rnotns iiye in an enyironrnent wnere botn dark and iignt backgrounds are ayaiiabie Tne dark rnotn tnat cnose to rest on a iignt background or tne iignt rnot by tne nungiy predators and eaten tnan wouidtne rnotn tnat rested oniy on backgrounds tne sarne coior as its body A gene tnat disposed a rnotn to rest on dark ratner tnan iignt backgrounds would be a good idea for dark rnotns but not for iignt rno s LikeWise a genetnat disposed a rnotn to rest on iignt ratnertnan dar backgrounds would be a good idea for iignt but not for dark rnotns in sucn a situation it gene tnat is tnese bodyecoiof and festecoiof genes may coevolve sucn tnat rnotns Witn dark bodyecoiof genes aiso naye dark festecoiof genes and tnose Witn iignt bodyecoiof genes aiso naye iignt festecoiof genes To protect sucn fayorabie cornbinations of coeoived genes our rnotns snouid snow positive assortment in tneir rnating W tnat iS I ey snouid cnoose as rnates indiyiduais sirniiar to tnernseiyes if darkebody darkefestmoths mated Witn iigiilrbody ii inter trn tn rn of causing tnern to rest on backgrounds tnat don t rnatcn theifbodyecoiofs in ektrerne cases tne reproductive isolation of dark frorn iignt rnotns rnignt eyen iead to tne creation of two different species of rnotns Characteristics With No Adaptive Value it is ternpting to try to ascribe sorne ada tiye yaiue yaiue for suryiying and reproducing to eyeiy obseryabie cnaracteristic of eyeiy organisrn rn ntion racial differences in the shape 0 noses Are tnese differences tne resuit of naturai Seiection i i snapes for tnose tnat eyoiyed in cooiefciimate57 Perhaps pernaps not Tne raciai differences in nose snape couid be due to genetic drift Wnen tne size of a breeding p p g Smaii g in any Characteristic sucn a snape of nose couid be eiirninated Pernaps tne group S of number snapes of tneir raciai group s noses Page 14 Another possibility is that an observed characteristic is vestigial that is it was adaptive in the species evolutionary history but is no longer For example we have an appendix that apparently was useful in our distant ancestors but is of no apparent use now Since it is not very detrimental we are stuck with it If it were very detrimental to have an appendix over time natural selection would remove it Gray page 80 uses the clinging response of prematurely born infants as an example of a vestigial behavior they cling in a way that would be adaptive in our distant ancestors who were a lot more hairy than are we now Some characteristics may have desirable effects in one stage of life but undesirable effects later in life For example some diseases may be caused by genes that give younger humans a reproductive advantage but which cause illness later in life For example some genes that contribute to the development of high blood pressure later in life might during early adulthood make the individual more capable of competing for mates It is also possible that an observed characteristic is not adaptive in its own right but is just a sideeffect ofanother characteristic that is adaptive Gray uses the example of the amazingly large clitoris about the same size as the male s penis found in spotted hyenas During copulation the male s penis must be inserted through the female s tubular clitoris and during birth the babies must pass through it Ouch One explanation ofthe evolution of this enormous clitoris is that it is a side effect of natural selection for large size and aggressiveness in female spotted hyenas the females are largerthan the males and dominate them Proximally the large size and aggressiveness of the female hyena is produced by her having high levels of androgens hormones including testosterone typically found in high levels in male but not female mammals Spotted hyena mothers androgens affect the prenatal development of her daughters causing them to grow enormous clitorises Sociobiology of Sex Differences in Reproductive Behavior The basic premise of sociobiology is that our and other species39 common behavioral patterns are the result of many generations of natural selection selecting behavioral patterns that enhance reproductive success In short genes that are especially successful at reproducing themselves including genes that in uence social behaviors will eventually be the most common genes in a population Can sociobiology explain differences between females and males sexual strategies In many species the females tend to be cautiously selective in their choice of a mate They look for evidence of health and vitality and for a commitment in time and resources to help in raising their young Males seem to be less selective in choosing with whom to have sex and are typically more assertive in seeking sex Why 1 Cheap Sperm Expensive Eggs One potential answer has to do with the fact that females have more invested in each egg than do males in each sperm Eggs are much larger and take more energy and materials to produce The female produces far fewer eggs in her lifetime than does a male produce sperm Female mammals investment also includes the costs Page 15 of bearing the fertilized eggs in the womb and then nursing the offspring after birth Given the female39s great investment in each egg she might be expected to be more choosy in picking a mate than is the male whose sperm are a relatively cheap expense to risk I Testing the Male In some species the female may seem to resist the male39s sexual advances at rst testing his resolve If the male does not persist he may not be the healthy vigorous sort of male that is most likely to have quotgood genesquot for her offspring Accordingly genes that dispose a male to be sexually persistent should replicate themselves better than do genes that dispose a male to giveup quickly The female may enhance her own reproductive fitness by accepting only persistent males males who will give her sons the genes that make them persistent maters also and such sons should further the female39s reproductive success by giving her lots of grandchildren Parental Care Why is it that in most species it is the female rather than the male that is the primary provider of parental care Here are some potential explanations 1 Parental Certainty It is wasteful in terms of propagating your own genes to spend a lot oftime investing in offspring that are not yours unless they are nonetheless very closely related to you for example your nieces and nephews In mammals the female is always more certain of her maternity than is the male of his paternity for obvious reasons 2 Greater Initial Investment As discussed earlier females have much more invested in each egg than do males in each sperm Some opine that this should make the females more interested in caring for the offspring protecting their investment than are males Others argue that past investment quotsunk costquot is irrelevant in making correct decisions regarding present or future investments They speak of the quotConcorde fallacyquot referring to the continued French and British investment in a ying machine at a time that it appeared it would never make money much money had already been poured into the project Having foolishly spent millions on something is in itself no good reason to continue to do so Thus even though his initial investment is much less than that ofthe female the male should invest heavily in offspring that are his own unless he can more effectively channel his reproductive energies elsewhere Assuming that the mother and the father have equal numbers of offspring which would not be the case in a quotharemquot mating system where each successful male would have many more offspring than each mated female the father should then give each offspring as much care as does the mother 3 Facultative optional Paternal Care Males may be quite willing to stay home and invest heavily in their offspring unless and until the opportunity arises to engage in a yet more effective way to propagate their genes such as seeking copulations with other females Males may be especially likely to seek extra mates when times are good when the environment is rich since during those times the Page 16 mother who cannot so easily enhance her reproductive tness by seeking extra copulations remember sperm are cheap eggs are not can probably take care ofthe offspring without as much help Also the male is more likely to quotstrayquot when his mate is not receptive for example when she is incubating eggs since he has no risk of being cuckolded in his absence This alternative strategy increase the number of children you produce by seeking extra copulations is not available to the female the maximum number of offspring she could produce is very much less than that a male could This should also mean that she should be very interested in mating only with very good males males who have good genes and who have control of resources essential to help her reproduce Of course the female may be able to raise her reproductive fitness somewhat with some careful quotextrapair copulationquot if she can obtain genes and maybe also parental resources from another quotbetterquot male and if she does not get caught in which case her mate may abandon her or he may kill the offspring Sociobiology of Mating Systems Robert Trivers with whom I presented a symposium on paternal care at the annual meeting of the American Society onoologists back in 1983 has proposed that there will be a correlation between the mating system typical of a species and the parental investment of females versus males Parental investment involves the allocation of total lifetime resources devoted to rearing current offspring Investing heavily in the rearing of current offspring can reduce the amount of investment possible for producing future offspring Polygyny In this breeding system each breeding male mates with several females and most males do not breed This system is associated with species in which the maternal investment is much greater than paternal investment This describes the situation for mammals as we discussed earlier Cheap Sperm Expensive Eggs and most mammals are in fact polygynous In this circumstance a male s reproductive success is largely a function of how many females he can breed with This leads to natural selection of characteristics that enable males better to compete for access to females Such characteristics typically include great size strength and aggressiveness Females cannot greatly enhance their reproductive success by mating with many males but they may well be able to enhance their reproductive success by choosing to mate with the male who wins the competition among males since that male should provide her sons with the genes that would dispose them to be successful breeders too In some species when a male takes over a breeding group from another male he may kill all babies in the group and may even induce abortion in pregnant females In that way the new stud can start passing on his own genes more quickly than if the females were allowed to continue raising their current babies Polyandry In this breeding system each breeding female mates with more than one male and some females don t get to mate This system is associated with paternal investment being greater than maternal investment and has been observed in some species of birds and sh One interesting example is the American iacana pronounced zh san These birds live in wetlands where their elongated Page i7 u g Each territory Each temale detends a large territory which includes theterritories or as many as tourmales Onl the males proyide parental care Femaies exciude other temales trom their territories it atemale is successtul in taking oyer another femaie s mate she may le tr own Jacanas and Poi andn 7 includes a nice PBS yideo clip Monogarriy The basic idea here is that each breeding animal is mated with one member or the opposite sex These pair bonds may be tor litetime or may only be tor m i do sometimes mate with indiyiduals other than their primary partner as so called extra pair copulation it has been determined that as many as one third or the ottspring or monogamous birds were actually tathered by a male other than the one attending the nest yery dif cult to 39 39 39 parent Most birds are monogamous Unilke with mammals the male and the remaie are egua iy other l m in i hi up ii i in iiiiiw but also meat and the male can assist with the proyision or meat Polygyaridry Here there is more than one temale and more than one male in individualism chimpanzees arid bonobos Bonobos and humans are by the way the only primates their p Sexuai heat near ovuiatlon Sociobiology of Altruism Altruistic behayior is that which increases the reproductiye potential of another behavior since genes are SeiflSh as that is the genes that will be faored by natural selection are those that are better at reproducing themselyes than are compe ing enes expialn apparently altruistic behayior Kin Selection According to this theory a gene that disposes an indiyidual to haye in apparently altruistic ways can actually haye a selectiye adyantage it such altruistic behayior is directed only at others who are i elyto avet e same gene that is only towards close kin A large body or research indicates that many animals are indeed much more ilkeiy to show altruism towards kin than towards nonle Page 18 Reciprocal Altruism The basic idea here is that apparent altruism may actually be a case of I ll help you if you ll help me That is it is longterm cooperation in which both parties gain For reciprocal altruism to evolve individuals must be able to remember who has returned the favor and who has not and then decline to be helpful in the future to those who have not returned the favor Ethology and SpeciesTypical Behaviors A speciestypical behavior is one which is the same in all members of a species Such behaviors are thought to be automatically produced by speci c environmental stimuli The stimuli are referred to as sign stimuli and the behavior as a xed action pattern Gray gives an example involving Tinbergen s study of reproductive behavior in the stickleback an European sh During the breeding season the male stickleback builds a nest and defends it against any male intruders When a female stickleback enters his territory he displays a zigzag dance which is designed to convince the female to lay her eggs in his nest During the breeding season the males belly swells up and turns red Tinbergen found that the swollen red belly serves as the sign stimulus which releases the attack on intruding conspeci c males Models of objects with swollen red bellies released the fixed action pattern even when the model did not othenNise even look like a stickleback Models in which the swollen red belly was even more prominent than it is in a real stickleback were especially effective at releasing the attack behavior Ethologists have a great interest in studying the speciestypical behaviors of animals and comparing different species of animals with the goal of determining why different species have evolved their particular speciestypical behaviors Gray mentions the use of homologies and analogies in such comparisons A homology between two species is a similarity that stems from their having a close common ancestor For example the flipper of a whale and the arm of a human have very similar structures despite their having quite different functions A analogy is a similarity that stems not from common ancestry but rather from having independently evolved similar ways of dealing with similar problems For example consider the wings in birds insects and bats species that are not closely related quotWm Lesson on l39 39 39 and Analoqies 0 Gray discusses hive building in bees and smiling in humans as examples of attempts to reconstruct the evolution of a speciestypical behavior I shall use a different example vampirism in moths No I am not kidding there are actually vampire moths Hans Banziger offered his cut finger to a species of moth found in Southeastern Asia Calpe eustn39gata and discovered that the moth not only consumed the blood but actually pierced the esh with its proboscis How could this species have evolved vampirism 0 Most moths have a delicate proboscis used to suck nectar from flowers f most members of a group of closely related animals share some trait then a Page ta common ancestor probabwy had that trait 00 so we concwude that the tirst rnoths were nectarefeeders Many moths suppwernent their diet by teeding on the sugars ot damaged nuwts and by obtaining sawt an other rnineraws trorn drwnkwng rnud puddwes unne or other anirnaw secretions it is assurned that one ot these sorts ot rnoths was ancestraw to yarnpire rnoths i m i i i ruits and causethern toweak Tnese rnoths haye strong proboscis ans represents another step towards yarnpr n even fe specie eti of the proboscis are fwnnen awwowingthe rnoth to use the proboscisto cut directwy into tnwckeskwnned truits such as oranges er hairs at tip of their isrn species or piercing Aswan Vamgwre Motn 7 see ne Aswan vampire rnotn Butter Proboscws rwncwudes rnentwon oftne Aswan Varnpwre Motn Carowwna Sgnwnx Motn r cneck outtne proboscws 0n nws beast Gray warns us of two tawwacies to ayoid when atternpting to use sociobiowogicaw principwes to expwawn hurnan behayior 39 39 ans is theo ii i 39 39 For exampwe it naturaw sewection has resuwted in hurnan beings being Warewwke creatures then that is a good thing ans does not reawwy make any sense because naturaw se ect on are rnorawwy correct 39 39 39 ans is the bewiet e behavior which is at least in part determ39 ge s w tact we rnay not be abwe to do anything about the behayioraw dispositions we inherit but we certainwy can restrain sorne o t ern and encourage others otthern by changingthe wiye wn ta t of Tn sort of institutions w arn nwnkwng of are rewigious cuwturaw sOCwaw and goyernrnentaw Page 20 institutions Ifonly such institutions were to act in the best interest ofthe people I fear however that such institutions are subject to the same sort of sel sh evolutionary processes that make individuals most motivated by selfinterest Those institutions that have attributes that promote their institutional survival and reproduction will dominate even it that involves sacrifice ofthe individuals within such institutions until the revolution that is Revised March 2006 Illustrations now have alternative text Back to the PSYC 1000 Lecture Notes Pade Motivation Sleep and Emotion This is my favorite chapter in our text It covers most of the things I most enjoy such as eating drinking and sex I could spend the whole semester talking about these things but will try at least a little to restrain myself Introduction quotMotivationquot refers to the study ofthose hypothetical internal states motives that cause an organism to behave in seemingly goaldirected behavior For example the study of what it is that makes one hungry and how it is that eating turns off that hunger falls within the domain of motivation When a basic biological quotneedquot is unsatisfied a drive is engaged This drive activates the organism and may direct it towards behaviors that are likely to satisfy the need The activation and deactivation of drives may be viewed as part of a homeostatic regulatory mechanism designed to keep the values of various physiological parameters within certain boundaries For example if your body temperature drops you become motivated to increase activity eat more move to warmer places et cetera When such behaviors reduce the drive by warming your body back into the desirable range of temperatures the behaviors that led to such drive reduction may be reinforced Do note that not all basic biological needs have specific drives associated with them For example although we have a basic biological need for oxygen we have no drive for oxygen We do have an air drive a very strong one as you discover when you try to hold your breath for long In the environments in which our ancestors evolved there was a nearly perfect correlation between presence ofair and presence of oxygen so an air drive was quite suf cient Modern humans do sometimes encounter oxygenless air for example at very high altitudes flying or in carbon dioxide dry ice refrigeration chambers The hypoxia that results from being in such oxygenless air is actually pleasant but deadly Some goal objects are so desirable that they engage behavior to obtain them even in the absence of obvious drives Such motives are called incentives lfdrives are the push of motivation incentives are the pull For example ifl am very hungry I will eat those turnips and stale bread in the refrigerator as they do satisfy my need for calories f relatively foodsatiated I39ll have nothing to do with the turnips but the great incentive value ofa pizza mightjust well pull me to eat it Some psychologists suggest that there are motives that do not satisfy biological needs such as curiosity In my opinion the failure to see the biological basis for such motives is due to psychological myopia What does the curious animal obtain when exploring all around its environment It may obtain new sources of food and water it may find new mates it may find places to hide from predators and adverse weather and many otherthings ofobvious biological value Finding these biologically important things would be expected to increment the reproductive fitness ofthe curious Gray6doc Page 2 animal leading to the natural selection of a quotcuriosity drivequot in some species including humans Physiological Techniques for Studying Motivation The focus in Chapter 6 of Gray is on discovering the physiological mechanisms involved in motivation Social and cultural influences will be discussed later Lesions We can destroy specific areas of the brain and then see how the animal s behavior changes For example if we destroy a certain area and then the animal no longer responds to food then we may have found an area involved with the hunger drive There are several ways we can create lesions We could sink an electrode into a particular brain area and apply enough shock to destroy that brain area Alternatively we could sink a cannula a tiny tube into the brain and use it to apply chemicals that would destroy particular neurons lfthe target area is close to the surface of the brain we can just suck it out with a small vacuum Brain tissue is not very firm Stimulation We can apply a small shock through an electrode to stimulate a particular area ofthe brain or we can apply chemicals through a cannula to stimulate particular neurons For example ifwe stimulate a particular brain area and then a previously satiated animals starts to eat we conclude that we have found a brain area involved in hunger Knockout Animals lfwe wish to determine the effect of a naturally occurring brain chemical we can use genetic engineering techniques to produce animals that do not have the gene necessary to make that chemical Comparisons between the behavior of such knockout animals and normal animals may tell us how the missing brain chemical is involved with motivation Recording We may employ techniques that allow us to record what is going on in the brain while the animal is in certain drive states or engaging in certain behaviors This may be done electronically via electrodes inserted into the brain or through brain scans like those we discussed in the last chapter We may also be able to extract brain chemicals from particular brain areas and note how they change when the animal is in different drive states Hunger Turning Hunger On Our body has several mechanisms that signal the brain if the level of nutrients in our blood drops dangerously low The brain then responds by activating hunger One such mechanism is a sugardetector in the hypothalamus The liver also monitors levels of nutrients in the blood and passes that information on to the brain These mechanisms may however never come into play in animals that are always well fed like you and l The levels of nutrients in our blood are nearly constant because when they start to drop our body compensates by converting fat to nutrients in the blood More important for us may signals from the fat storehouses Fat cells secrete a hormone called leptin in proportion to the amount of fat they are storing This hormone is carried to the hypothalamus where it inhibits the production ofa slow neurotransmitter called neuropeptide Y Neuropeptide Y is the most potent appetite Page 3 stimulant ever discovered It is distributed to various parts ofthe brain from neurons in the lateral hypothalamus in an area called the paraventricular area This slow transmitter produces effects that last up to several hours Classical conditioning may also contribute to the initiation of hunger Like Pavlov s dogs stimuli such as the time of day and the sight and smell of food come to elicit anticipatory responses such as secreting saliva other digestive juices and insulin Stimuli resulting from these anticipatory responses are associated with hunger causing us to feel hungry at certain times ofthe day or when we see or smell or just think of food The conditioned release of insulin may also contribute to hunger by triggering a small but rapid drop in blood sugar which should be detected in the hypothalamus Turning Hunger Off How does the brain know when to turn off hunger It could just wait until levels of leptin or blood nutrients returned to their normal levels but if we kept on eating until that happened we would be eating too much The brain needs to be able to turn off hunger after we have eaten just enough which is generally well before the food is digested and excess nutrients converted to fat There are a number of afferent inhibition systems that monitor eating and turn off hunger after enough has been eaten but before it is digested Afferent means from the outside to the brain so afferent pathways are sensory pathways Signals from the muscles involved in chewing and swallowing and from stretch and food detectors in the stomach tell the brain how much has been eaten and when enough has been eaten the brain turns off hunger temporarily lf normal levels ofleptin and nutrients in the blood are not restored after a while then hunger is turned back on Humans sometimes use such afferent inhibition to try to keep hunger turned off by chewing gum or by swallowing dietaids that swell up in the stomach Overeating in some persons with anosmia may be related to the fact that they do not get afferent inhibition from the smell of foods they eat Researchers cut an esophageal fistula hole in the throats of each of several dogs so that food that they ate would not reach their stomachs Such dogs do stop eating after eating about as much as they normally would the afferent inhibition from chewing and swallowing is effective in turning off hunger but since the nutrients are never absorbed into the blood the hunger returns after a half hour or so Obesity Most persons in our society eat too much Why The simple answer is because they can It seems that most of us have genes that dispose us to eat up all the high calorie food we can get into our mouths This does not seem very adaptive so why do we have these genes To answer that question we have to consider the environment in which our ancestors lived They lived in feast or famine environments where those high calorie foods were not often available To survive in such an environment it is adaptive to be disposed to eat as much as one can when such foods are available and then store away the excess in fat cells to be used during future periods of famine Genes disposing one to engage in such quotpigoutquot behavior were selected in our ancestors so we have them but we live in an environment where such high calorie foods are always available so we may become obese A similar explanation may apply to the high frequency of sugar diabetes in humans according to James Van Gundia Neel How could genes disposing one Page 4 towards sugar diabetes survive natural selection There is evidence that such genes actually promote metabolic thriftiness the ability to make the most of a few calories when present in certain genetic backgrounds giving them selective value for organisms that live in lean environments as our ancestors did but we now live in a calorierich world With those Old genes Neel J V 1962 Diabetes mellitus A quotthriftyquot genotype rendered detrimental by quotprogressquot Am J Hum Genet 14135362 Neel J V 1982 The thrifty genotype revisited In The Genetics ofDiabetes Melitus eds J Kobberling and R Tattersall pp 13747 New York Academic Press See also the document ObesityDiabetes and the Thrifty Genotype Hypothesis Our body s ability to adapt to famine conditions makes it dif cult to loose weight by dieting When we cut back on the amount we eat our body adjusts our basal metabolism such that we more efficiently use the food that we do eat Exercise can help by building up muscle tissue which burns up more calories My dilemma is that when l exercise my joints give me bad pains when I don t exercise I gain weight Gray notes that in Western cultures where highcalorie food is abundant most of the differences in body mass index ratio of body weight to height are due to genetic rather than environmental factors This is simply because the food environment is so uniform in those cultures you can get your high fat junk food almost anywhere in the industrialized world So what is it genetically about some people that makes them even more prone to obesity than are other people Efficiency of metabolism may be one factor Those who are very good at extracting energy from food and storing away the excess in fat will be prone to obesity Another possibility is genetically based differences in hunger locus of control the extent to which one s eating is affected by external factors rather than internal factors Stanley Schachter proposed that persons differ on a dimension anchored on one end by quotinternal eatersquot persons whose hunger is controlled only by internal physiological factors and on the other end by quotexternal eatersquot whose hunger is controlled only by the sights sounds smells and tastes of food In our culture where the stimuli associated with high calorie foods are so ubiquitous the external eater may be doomed to obesity Let us review some ofthe evidence for Schachter39s idea Stunkard Psychsomatic Medicine 1959 1 281289 had subjects swallow balloons to monitor their stomach contractions The correlation between selfreports of hunger and stomach contractions was higher in nonobese subjects internal eaters than in obese subjects Schachter put obese and normal weight subjects on a bland but nutritious diet in a hospital The normal weight subjects maintained their normal caloric intake and weight but the obese subjects external eaters dramatically reduced their caloric intake and weight until they were released In another study Schachter provided student subjects with a box ofWheat Thins to eat while they were involved in some tasks during a twohour experiment For some subjects the clock had been altered to run fast for others to run slow The speed of the clock an external stimulus had little effect on the number of crackers eaten by the normal weight subjects but obese subjects ate more when the clock ran fast Page 5 In another experiment Schachter39s subjects were told they had to wait a while before starting the experiment For one group of subjects the waiting room had a table of roast beef sandwiches to which the subjects were invited to eat For another group subjects were invited to go down the hall to a refrigerator to get sandwiches if they got hungry The location of the sandwiches had little effect on the amount eaten by the normal weight subjects but that external factor did affect the eating behavior ofthe obese subjects who could resist the sandwiches down the hall but not those right in front ofthem The Hypothalamus Earlier I mentioned the production of neuropeptide Y in the lateral hypothalamus There is also evidence from lesion and recording studies indicating that the lateral hypothalamus is involved in hunger and eating Lesions in the ventromedial hypothalamus have been demonstrated to cause animals to become obese These lesions alter digestive and metabolic functions such that the lesioned animal more quickly digests it s food and converts it to fat Check out the picture on page 194 of your textbook The obese rat there weights about three times as much as does a normal rat Thirst Osmotic thirst There are two kinds ofthirst osmotic and volemic Your body needs to maintain the saltiness of your body uids at about 09 lfyour uids get too salty detectors in the hypothalamus engage osmotic thirst You seek and drink water which dilutes the saltiness ofyour body uids back to normal levels Pure saltfree water is most effective in reducing this thirst Sea water is usually about 35 salt while our body uid is only 09 salt Accordingly drinking sea water will actually make you more thirsty due to increasing the salt concentration ofyour body uids Tavern and bar owners may manipulate your thirst by giving you free salty nuts and pretzels The salt makes you thirsty so you buy more beer Additionally the alcohol interferes with the antidiuretic effect ofthe hormone vasopressin which normally causes you to reabsorb needed water before excreting it in urine so you pass too much water and stay thirsty beer after beer Volemic Thirst When you sweat or loose blood you loose both water and salts Both must be replaced The volemic thirst that results is best satis ed by fluids that contain salt in about the same concentration found in normal body uid for example Gatoraide It was once thought that a hormone angiotension secreted by your kidneys when blood volume drops was responsible for engaging volemic thirst but it is now known that the amount ofangiotension released when body uids are low is not enough to cause thirst but it is enough to have other pressurerestoring effects on your cardiovascular system Stricker amp Verbalis 1988 American Scientist 76 261267 There are baroreceptors in smooth muscles in your cardiovascular system that do stimulate volemic thirst when blood pressure falls Sexual Motivation Effects of Sex Hormones on the Prenatal Human lf androgens male sex hormones including testosterone are not present during quotcritical periodsquot very early in life before birth the human develops as female regardless of its chromosomal sex Page 6 Normally the XY human fetus produces the androgens that cause it to develop as male rather than as female The masculinizing effect of early exposure to androgens is not only on genital 39 39 It but on 39 39 It of the brain as well Early exposure to androgens causes the brain to develop in ways that produce stereotypically masculine rather than feminine behavior The gene responsible for the production of these androgens has been identified see Time July 30 1990 page 53 Four men with XX chromosomes were found to have the maleness gene which usually is on the Y chromosome on one of their X chromosomes XY female mice have been shown not to have the maleness gene on their Y chromosomes The Research of J Money Sometimes unusual events occur during early critical periods and the XY human develops as female or the XX human as male The sex of the baby may be ambiguous as judged from its genitals for example an XX baby with an enlarged penislike clitoris and fused labia vaginal lips somewhat like the female spotted hyenas we discussed earlier Such individuals are sometimes called quotpseudohermaphroditesquot J Money is best known for having studied such individuals in the latter half ofthe 1900 s Here are some examples from his research 1 An XX human is exposed to androgens prenatally the pregnant mother is treated with androgens or has an adrenal gland disorder that causes her to produce more androgens than women usually do The child is born with a penislike clitoris that is surgically altered and the child is raised as a girl Such girls do show some signs of behavioral masculinization from the early exposure to androgens for example playing more with boys than with girls and aspiring to quotmasculine professionsquot such as being an auto mechanic rather than to motherhood 2 An XY human does not produce androgens during its sensitive period or has cells that are not responsive to androgens The child is born with female external genitalia and raised as a girl The abnormality is rst discovered when she does not menstruate The child generally develops a female sexual identity Treated with female hormones she will develop breasts but cannot reproduce 3 A boy had his penis mangled in an accident He was given a sexchange operation and raised thereafter as a girl At age 4 she appears to have developed a normal female sexual identity but by age 13 she has developed a masculine walking gait is called quotcave womanquot by her peers and aspires to become an auto mechanic Recent Research With Money s Previous Subjects Money s research was initially interpreted as indicating that humans are born gender neutral and that gender identity is something that is learned rather than biologically determined Other researchers have recently contacted some of Money s subjects now that they have grown up and the radical environmentalists interpretation has been seriously challenged Milton Diamond and Keith Sigmundson contacted one of Money s former patients The child was born in 1963 At 7 months of age he was subjected to circumcision by electrocauterization In this procedure the foreskin ofthe penis is burned offelectrically There was a surgical accident and the boy s penis was damaged at the base It died and fell off At 21 months of age the child was castrated Page 7 and a pseudovagina was surgically constructed The idea was that a child without a penis would have problems if raised as a boy so just make him into a girl Diamond and Sigmundson referred to this child as Joan Money kept track of Joan until she was 9 years old He reported that she was somewhat tomboyish but that her gender identity was that which is normal for a girl This however is not what Joan told Diamond and Sigmundson She told them that whenever her mother would put her in dresses she would tear them off She preferred playing with boys toys like toy machine guns She insisted on urinating from a standing position which tended to make a mess ln junior high the other girls would not allow her in their restroom When she was 14 she decided that she was either going to live her life as a man or kill herself It was then that her father nally told her about her sex reassignment Joan is now John having had a pseudopenis surgically constructed and receiving testosterone replacement therapy At age 25 John married a woman and adopted her children He says his sexual attraction is exclusively to women If you would like to read more about this case here are some links Rolling Stone article bv John Colapinto 1997 Archives of Pediatric amp Adolescent Medicine 1997 Diamond amp Sigmundson BruceBrendaDavid Reimer 1966 2004 CBC News Reimer Takes His Life 0 What were the real reasons behind David Reimer39s suicide In 1978 a second study ofone of Money s previous subjects was published Like John this child lost his penis during circumcision by electrocauterization At 7 months of age child was castrated and surgical repairs were made to allow the child to be able to urinate The child was then raised as a girl At age 16 this child reported having problems with the remaining stub of her penis It would become erect at times causing embarrassment especially when she was wearing a bathing suit At this age she received surgery to construct a pseudovagina She denied having any problems with gender identity At age 26 she had additional surgery to make her pseudovagina suitable for intercourse with men it was too small following the first surgery She reported that she had sexual relationships with three men and three women She said male genitalia looked funny to her and that she found naked women more attractive than naked men She was sexually attracted to men only when they were wearing clothes This woman is reported to have been employed in a bluecollar occupation which is practiced almost exclusively by men Read the article PEDIATRICS Vol 102 No 1 July 1998 True Hermaphrodites A hermaphrodite is an animal that can produce both eggs and sperm Although rare there have been identified humans that are true hermaphrodites A true hermaphrodite results when two fertilized eggs one XY and the other XX fuse in the womb Such an individual is a tetragametic chimera Page 8 tetragametic because it was formed by the union of four gametes two sperms and two eggs A chimera is an individual in which there are two genetically different populations of cells originating from different zygotes In Greek mythology a chimera was a creature that was part lion part goat and part snake Although human chimeras can occur naturally it is more likely to happen when multiple embryos are transferred artificially into a woman s womb lfyou would like to read more about true hermaphroditism in humans read the articles on this topic posted in BlackBoard under Articles One of the articles even include photographs ofthe genitals of a true hermaphrodite Sex Differences in Tests of Cognitive Ability lfearly exposure to androgens causes the brains of boys to develop differently than the brains of girls then one might expect to find sex differences on almost any attribute that is associated with the brain One such attribute is cognitive abilities Sex differences in tests of cognitive abilities were reported by Janet Hyde 1981 American Psychologist 36 892901 to average 14 of a standard deviation on tests of verbal ability female mean higher and 12 of a standard deviation on tests of visualanalytic spatial ability male mean higher Statisticians generally consider a difference of 15 of a standard deviation to be a small but not trivial difference a difference of 12 of a standard deviation to be a medium sized difference and a difference of 45 of a standard deviation to be a large difference One half ofa standard deviation corresponds to 100 points on a total SAT score for example Hyde points out that even relatively small differences in the means of two normally distributed distributions lead to very large differences in the tails of their combined distribution For example even though girls39 mean verbal ability is only 14 standard deviation higher than boys if you look at who it is that is in remedial reading programs you will find three boys for every girl lfyou look to see who it is that scores 700 or more on the Math SAT given to Talent Search seventh graders you will nd 17 boys for every girl These are not small differences Geschwind amp Behan quotLaterality hormones and immunityquot in Geschwind amp Galaburda39s Cerebral Dominance The Biological Foundations Cambridge MA Harvard Univ Press 1984 has attributed such mathematical precociousness and also lefthandedness nearsightedness and a tendency to suffer from allergies and asthma to the effects upon the brain of exposure to high levels of testosterone early in life There is danger in the statistics l have provided you above It would be a potentially big mistake for a woman to conclude that she should not go into a profession that requires good math skills simply because she is a woman Many women are much better at math than most men and these women should be encouraged to go into mathrelated professions Likewise not all men are verbally de cient One should base his or her vocational choices on demonstrated individual strengths and interests not on those typical of one39s sex The real tragedy in my mind is the sextyping of cognitive skills that takes place in boys and girls who strive too hard to meet the expectations of others who have such rigid sexual stereotypes While sex differences in tests of cognitive ability are IMHO not small they are also not fixed in size For example there is research demonstrating that the difference Page 9 between men and women on spatial ability can be reduced if women are given practice on tasks that exercise their spatial abilities There is evidence that the size of sex differences on tests of cognitive ability has decreased since the time of Hyde s 1981 study For example Hyde et al Psychological Bulletin 1990 107 139155 reported that when more recent studies were included in her analysis the difference between men and women fell to near zero in the general population When the analysis was restricted to elementary school students the girls did slightly better than the boys Male high school students did better than their female peers d 29 and male college student betters than their female peers d 32 The most recent research l have read Hyde American Psychologist 2005 60 581592 indicates that sex differences are near zero on many attributes but remain on some Here are a few where the sex difference is not trivial Negative values of d indicate that women did better positive values indicate that men did better Janet Hyde also reported sex differences on a variety of other attributes Here are a few ofthem lndirection aggression here refers to the social rejection or ostracism of the target of the aggression including spreading nasty gossip about the target and displaced aggression slamming doors for example The reported valued of d is from Archer Review of General Psychology 2005 8 291322 and is based on four studies where behavior was directly observed Sex Differences on the SATVerbal For many years women outscored men on the verbal section of the SAT However from 1972 through 1985 and in every year since then men have outscored women on the verbal section of the SAT In 1985 the gap was 12 points on the verbal SAT and considerably larger on the math section l have been unable to nd more recent data the Educational Testing Service has done a good job of hiding it recently Why did the scores of women decline more rapidly than the scores of men One hypothesis see the APA Monitor June 1986 pages 3031 Page 10 supposes that the shift is due to a change in who it is who is aspiring to go to college and thus taking the SAT In this country women have to get a college degree to have a chance to get a job that pays as well as do the jobs that men can get with just a high school diploma This may result in a large number of scholastically weak women taking the SAT while scholastically weak men just go get a good paying job and don39t bother with college orthe SAT arti cially depressing the mean SAT of women Some have proposed that the decline in women39s SAT scores is due to the fact that women are engaging in sexual behavior earlier than ever before and such activity may detract from their schoolwork It should be noted that women do obtain better grade point averages than do men but some critics opine that this is so because they take courses that grade easier than those that men take my own research indicates that women at East Carolina University tend to work up to their full potential doing as well in a course as their abilities and skills allow while men do well only if they have the ability and are interested in the material being taught Experimental Studies With Laboratory Animals The effects of early exposure to sex hormones can be experimentally studied in laboratory animals The animals are typically neutered and then treated with hormones The typical nding is that early castration ofa male results in an animal that is somewhat like a female in its adult behavior on several dimensions lfa female is neutered and treated with male sex hormones she may as an adult show more masculine behaviors than do normal females One example of such an effect is the effect of early hormonal experience upon rats39 spatial abilities Males tend to have better spatial abilities than females in species where learning its way around large areas is very important to a male39s reproductive success but not to a female39s for example in a species where the male attempts to mate with many females who are spread out across a large area Castrating a male rat early in life reduces his spatial ability later in life and giving male sex hormones to a female rat early in life increases her spatial ability later in life see Goy amp McEwen 1982 Sexual differentiation ofthe brain MIT press Female rats perform better than male rats on some tasks such as passive avoidance tasks learning what not to do and early hormonal treatment can alter rat39s ability to perform such tasks too The critical period for the effect of androgens on the brain is later than the critical period for its effect on the genitals Researchers have manipulated androgens to produce animals with the genitals of one sex and the brains and behavior ofthe other sex The Onset of Sexuality DHEA an androgen produced by the adrenal glands is responsible for the onset of sexual attraction in both boys and girls This typically takes place at about the age of 10 before puberty At puberty the production of testosterone in young men and estrogen in young women causes sex speci c changes such as the growth of facial hair and breasts Effects of Sex Hormones in Adult Males Testosterone is necessary for the maintenance of normal sex drive in men and other male animals Castration removes the main source oftestosterone and greatly diminishes sex drive Sex drive can be restored by injections oftestosterone into the bloodstream or the placement ofa tiny Page 11 amount oftestosterone in the medial preoptic area of the hypothalamus Lesions at this area abolish sexual behavior Effects of Sex Hormones in Adult Females In most female mammals removal of the ovaries the primary sources of estrogen and progesterone abolishes sexual behavior Sex drive can be restored by injections of these hormones into the bloodstream or the placement ofa tiny amount of them in the ventromedial area of the hypothalamus Testosterone produced in the adrenal glands of women is associated with sex drive Testosterone treatment increases sex drive in women who seek help for having low sex drive Sexual Heat Female sexual receptivity is associated with a distinct period of sexual heat near ovulation when hormone levels peak in most mammals but not humans For example in some nonhuman primates the female39s rump swells up and turns bright red and purple signaling to the males that she is sexually receptive Some have suggested that women39s use of red and blue cosmetics is a throwback to such a sexual signal Why is it that there is no such obvious signal of ovulation in humans and why is it that women may copulate at any time during their ovarian cycle One potential explanation for the lack ofa distinct period of sexual heat has to do with birth control lfthere were such a signal of fertility our female ancestors being rather intelligent and not always wanting the burdens of pregnancy childbirth and child rearing could have avoided pregnancy by avoiding sex at such times Genes that resulted in hiding ovulation would prevent such attempts at birth control and thus would be selectively propagated Another explanation has to do with the importance of paternal care Assume that children are more likely to survive and to do well if the man quotstays homequot and helps care for the children The man can choose to advance his reproductive success by seeking extrapair copulations or by staying home and helping care for the offspring Time he spends doing the one he cannot spend doing the other The woman is better off reproductiver if she can eliminate the man39s option of seeking extrapair copulations in which case the only way he can advance his reproductive success is by contributing to the care of the offspring lfthe woman is at least somewhat sexually receptive most of the time rather than only during short periods around ovulation and if ovulation is hidden then the male is encouraged to stay home not only to be sure that he impregnates her but to be sure that no other male does so There is some evidence of behavioral effects of proximity to ovulation in women Women report only slightly higher sexual desire near ovulation Harvey 1987 J Psychosomatic Research 31 101110 but their behavior might reveal more In the best attended paper session I have ever attended two young women presented their relevant research at a meeting of the Animal Behavior Society in Knoxville TN One researcher had interviewed women prior to their entering a disco determining the date of their last menstruation Others observed the women inside the disco It was reported that women who were close to ovulation irted more wore more revealing clothing and wore more colorful makeup than did other women Correlates of Testosterone Level in Adult Humans of Both Sexes In women testosterone is positively correlated with Sex drive friendly sociability and Page 12 employment in professional managerial and technical professions Testosterone levels are highest among women who score quotundifferentiatedquot on the Bem Sex Role Inventory and who describe themselves as resourceful robust impulsive not rational and not civilized In men testosterone is positive correlated with Sex drive aggressiveness and antisocial behaviors criminal population and sensation seeking Dabbs and Ruback 1988 Bulletin ofthe Psychonomic Society 26 244247 who briefly summarized this research also presented data indicating that college men with high testosterone tend to be more heterosexually engaging friendly and charming than other male students and less arrogant and obnoxious than other male students They also tend to be somewhat undependable with a streak of erratic wildness Regulatory and Nonregulatory Drives Gray makes a distinction between regulatory drives and nonregulatory drives Regulatory drives are those that serve homeostasis that is they function to keep the level ofvarious internal parameters temperature volume of blood salinity of blood level ofnutrients in blood etc within certain limits These drives are said to serve tissue needs if the various parameters are kept with the desired limits then tissue will suffer or even die A nonregulatory drive is one that serves some other purpose Gray uses the sex drive as an example of a nonregulatory drive He says nobody can die from lack of sex lfyou don39t get enough sex you may feel like you are going to die but you won39t at least not sooner than othenNise We don39t need sex to survive but our genes do Making us have sex is how our genes reproduce themselves and thus continue to exist even after we die From the perspective ofthe gene sex is a most vital need Most modern biologists agree that humans have the genes that make us have moderately strong sex drives because those genes were better reproduced in our ancestors and passed on to us than were genes that would cause lesser interest in sex Sexual Behavior Gray discusses sexual motivation but he does not provide any description of sexual behavior itself I39m too interested in sexual behavior to let that slide Psychologists and biologists have done some really remarkable research on sexual behavior both in humans and in other animals We have a course in our department devoted to the topic of sexual behavior PSYC 4350 Psychology of Sexual Behavior My colleagues Susan McCammon and Clem Handron teach this course and do a fantastic job with it It does have a prerequisite of 6 hours in PSYC courses If you take 6 hours of PSYC and are interested in sex do consider taking this course I will have to restrain myself with respect to talking about sex I could spend the entire semestertalking about sex both sex in humans and in other animals The variety of sexual behaviors found humans is quite interesting but ifyou include other animals in your study of sexual behavior the variety is absolutely amazing Some of my attraction to the study of sexual behavior is due to the fact that I recognize that natural selection is a function of reproductive success and in sexually reproducing species sex is a big part of reproductive success but not all ofthe appeal is strictly intellectual I also nd the study of sex interesting just because it is just plain exciting to me on a primal level In this course I shall discuss only a few ofthe many interesting descriptions of sexual behavior with which I am familiar Page 13 The PostEjaculatory Refractory Period It is not uncommon for a male human or other animal to have a refractory period lasting from a few minutes to a day or more after an ejaculation during which he is incapable of being aroused to another orgasm with the same mate As we discussed earlier in the semester this postejaculatory refractory period is actively produced by the brain inhibiting rearousal right after an ejaculation It is biologically advantageous because continued copulation with the just mated female may interfere with the ability ofthe just ejaculated sperm to fertilize the eggs but this postejaculatory refractory period can be eliminated or shortened in at least three ways We already discussed the shortened refractory periods in dogs whose nervous connection between the brain and the genitals had been severed One event that can lift the postejaculatory inhibition is the presence of another female with whom the male has not recently mated It makes biological sense for the male not to mate with the same female right away but to mate with another The invigorating effect of a novel sexual partner is called the Coolidge effect after an incident involving President Calvin Coolidge The president and the rst lady were touring a farm When the rst lady stopped at the chicken pen she noted the sexual prowess ofthe rooster and asked the farm hand ifthe rooster performed like that every day The hand said yes and she asked him to tell the president that when he came by later Later when the farm hand relayed the rst lady39s comments the president asked if the rooster copulated with the same hen every time The hand replied no a different hen every time The president asked that the first lady be told that too Sexual selection is nothing more than natural selection where the attributes that are selected are those that help the individual compete with others for access to mates Sometimes such sexual selection involves males competing with one another for access to females Characteristics such as strength and aggressiveness are likely to be selected in such situations Sometimes sexual selection involves characteristics ofwhich make one more attractive to potential mates Typically it is the female who makes the choice regarding with whom to mate so characteristics which attract the female will be selected One popular example of such a characteristic is the fancy tail feathers on male peacocks Sometimes sexual selection takes place within the reproductive tract of females When females mate with more than one male close together in time the sperms ofthe two or more males compete with one another for access to the eggs This competition is referred to as sperm competition Sperm Competition Curt Busse and Dan Estep measured the postejaculatory interval in male monkeys that is after he ejaculates into the female how long is it until he attempts to copulate with her again For some monkeys they removed the female after the rst copulation and put her in another cage with another male who copulated with her while the rst male watched Then she was returned to the rst male They found that seeing a second male copulate with the female reduced the first male39s postejaculatory interval This makes biological sense Copulating again soon with the female allows the first male to interfere with the sperm deposited by the second male and to reinforce his sperms already competing with those of the second male to fertilize the eggs Estep Animal Behaviour 36 299300 has Page 14 also observed that the postejaculatory interval of the male roof rat is shortened if his mate copulates with another male shortly after copulating with him A similar observation has been made by a sociobiologist called Barash Mallard ducks normally pairbond mating with only one mate but stray males may attempt to force copulation on a female when her mate is away In normal copulation between mated ducks there is an elaborate courtship ritual foreplay that precedes copulation Of course the stray male forcing copulation hasn39t time for such as the mated male could return at any time and attack him The real surprise is what the mated male does when he returns and nds that copulation has been forced on his mate He immediately does the same with no foreplay Again this makes biological sense By immediately copulating with his mate he is able to more effectively compete with the sperm deposited by the strange male Penile Morphology W G Eberhard American Scientist 1990 78 134141 wrote an interesting article titled Animal Genitalia and Female Choice In this article he argues that sexual selection female choice of sexual partners and sperm competition has caused some interesting modifications in penile morphology He notes that male genitalia are often used as internal courtship devices inducing the female to use this male s sperm to fertilize her eggs rather than use the sperm of another male He notes that in species where females commonly mate with more than one male the penis has evolved to be longer to have more highly developed hard spines to have more complex shapes at the tip and to have a more developed baculum bone In such species there has also been sexual selection on behavior for example more elaborate copulation with prolonged and multiple intromissions He argues that females can use information from such internal courtships to decide which male s sperm to use to fertilize her eggs It is to her advantage to use the sperm from the best copulator since that should increase the chances that her sons will also be good copulators producing many grandchildren for her recommend this article for the curious it is worth reading if for no reason other than to see the photos and diagrams of strange penises Among the most amazing ones is that of the bedbug in which the penis has evolved in a hypodermic device with which the male can insert sperm into the female at a variety of sites from where they migrate through the blood to the ovaries In the medfly the penis is about 40 of the entire length of the insect Also interesting in the sea horse the female has a penislike ovipositor which she inserts into the male to transfer eggs into his pouch where they are fertilized Sperm Competition in Humans Recently there has been some speculation that women may sometimes encourage such sperm competition which could result in their obtaining superior genes for their offspring genes that make their male offspring have highly competitive sperm For example Bellis and Baker Animal Behaviour 1990 40 997999 found that pairbonded women are most likely to engage in extrapair copulations at those times when they are most fertile and with the copulations spaced to maximize the probability that two or more men s sperm will compete to fertilize the egg They also cited statistics indicating that levels of paternal discrepancy babies whose blood type indicates that the father is not the man the