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Biological level of an'alysis:genetics and behaviour

Behavioural genetics}lravioural genetics deals with understanding how both geneticsamri the environment contribute to individual variations in humanhahar.iour. It is interesting to note that humans share 93 per cent ofUrnes with the rhesus macaque monkeys, even though humans domst look like these animals and do not behave like them. Althoughmparative psychology has revealed similarities between humansamd monkeys, it is obvious that the 7 per cent difference in thegpnetic material accounts for a significant amount. This exampledsmonstrates the complexity of genetics; although the basic premisemff ffiis field is that inheritance of DNA plays a role in behaviour, it isummponant not to misunderstand this. What is inherited are the genesr[hn1 givg rise to the development of specific physiological processesrhnt contribute to specific characteristics and behaviour. It is notpmo,bable that a single gene is responsible for such complexhrhar-iours as intelligence, criminal behaviour, altruism, oramtachment. Instead, what is inherited may be one of the buildingMLmcks for such complex behaviours.$sl-chologists argue that an individual may have a geneticpredisposition towards a certain behaviour; however, without thedrypropriate environmental stimuli, this behaviour will not benrnanifested. For example, in the study of abnormal behaviour, thediathesis-stress model is used to explain the origin of depression.This model argues that depression may be the result of theumteraction of a "genetic vulnerability" and traumatic environmentalffimuti in early childhood. It is also known that not all peopledn-elop depression following a traumatic childhood, even if theyh,ave a sibling who becomes depressed. This illustrates thecnrnplexity of the problem and that there is no single cause-and-effect relationship between genes and behaviour.

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2_2 * B;e;or;.al level of analysis: genetics and behaviourGenetic arguments of behaviour are based on the principre ofnheritance. Genes and their DNA are passed down from parentso their offspring. T:lT, have Z'l parrs of chromosomes, wirhpproximately 2O 000_25 OO0 genes. In 1990, James D. Watsonioneered the Human C."o_Jp-j.ct, with the goal of mappinghe genetic make_up of the human species by identifying those5 000 genes' This incredibre pro;eciwas compreted in 2003. Theapping of human genes could be ahuman[.n"ti."1.;:;";'"".::.."^::-1]mportantstepinexplainingspecracurar".."il;i,1,ff11"1:f il.#i:f.:..:,,Tff ;"';iU:".*pecific behaviours remains unknown.

Genetic researchGenedc research in humans is to a large extent based oncorrelational studies. Researchers look at how different variabresay co-vary. This means that a correlationar ,r"av-"r.urrrrr., ,rru,here is a rerationship between "u.iuur.r, but the researcher does notanipulate an independent variable as in un expe.im".ri. rrr.."to.",o cause and effect can be determined.Twin studies, family studies and adoption studiesone of the most common ways to study the possible correlation ofenedc inheritance and behaviour is through twin research.Researchers study twins because tt.y rrru.. cornmon genetic materiar.There are two ryp:: o{rwins: rnonozygotic (Mz)and dizygoticD Z )' Mon o zy gotic rwins are g.".ti.uily ia.r,ii."r'u..u^.J.'ihey areormed from one fe,rtilizef _e_s;,h;;;;;r, into two. These twins aref the same sex and should il.t "..i-uch alike. Dizygotic meansrom two eggs. DZ twins will ,rot U" u.ry closer genetically thanrothers and sisters-they will rr"u. uuorr, 50 per cent of their genesn common. They are formed f.o_i*o separate fertilized eggs.hese twins are not necessarily of the s lbeca use pty.h "r;;i*s u se rh ese airfer.;1T:r*.rT'l:; ff:..' r',.relationship as a basis for rheir 6;;rh;r"r. Ir should be the case tharhe higher the genetic.etatlonrfrilf lfr. -o.. similar individuals wille if the particular characteristi. f.i"g'i""estigated is inherited. rnwin research, the correlarion ro""Jii called the concordance rate.Another way that behaviourar genetics is studied is through familytudies' Unlike twin researcrr, irri, irl -or" representative sampref the generar population. A .hiiJill.it, rrar irs genes from theother and half from rhe father. It f;ifu, rhar ordinary brorhersnd sisters will share 50 per cent of ,fr.i. g..r", with each other;randparents will share 25 per cent of their genes with theirrandchildren; and first cousinr ul rruu. r2.5 per cent of theirenes in common. In family studies, these different degrees ofenetic reratedness are compared with behaviour. The notion is thatoncordance rates win increase ir n.riaarility is high and vice versa.or example, if the heritability of fq n;lligence quotienr) is high,here should be a strong{orr"iurio"-i.r'ie o.r*..., children andheir mothers, but a weak correlation i.rlo n"r."een second cousins,nd very little, if any, betwee" ,,.""g..r.-

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2.2 a 3;61e9;.al level of analysis: genetics and behaviourA final method used for genetic research is adoption studies. Inprinciple, these allow the most direct comparison of genetic andmrironmental influences of behaviour. Adopted or foster childrengenerally share none of their genes with their adoptive parents, butmhev do share 50 per cent of their genes with their natural mother. Itwould be reasonable to suppose, therefore, that if the heritability ofa Lrehaviour is high and environment has little part to play, then theh'chaviour of adopted children should correlate more strongly withmhe behaviour of their natural mother than their adoptive mother. If,u'n the other hand, the environment has the strongest role to play,uhe reverse pattern should be found.Adoption studies are often criticized as these children are notrpresentative of the general population. In addition, adoptionagencies tend to use selective placement when finding homes fordrildren, trying to place children with families who are similar in asmany ways as possible to the natural parents. Consequently, theeffects of genetic inheritance may be difficult to separate from thefrnfluences of the environment.Or-erall, these approaches to the study of the relative influence ofgFnetic make-up and the environment allow researchers todetermine the extent of genetic influence. In spite of the weaknessesinutlined here, it is clear that there is a correlation between severalhehaviours and genetic inheritance.lnrtelligenceAt the beginning of the 20th century, there was a great interest inrhe role of genetics in behaviour. Governments and schools soughtro design tests that could indicate one's genetically endowedintellectual potential-or IQ. Alfred Binet, a pioneer in intelligencenesearch at the beginning of the 20th century, developed anintelligence test in order to improve the French education system.One of the main controversies regarding intelligence is whether it isinherited or is the result of environmental stimuli. At this point in:me, no serious researcher would argue that genetics does not playa role or that the environment has no importance. Research hasshornm, for example, that poverty seems to have an importantinlluence on the development of children's intelligence.Some intelligence research is controversial. In 1994, Harvardprofessor Richard J. Herrnstein published The Bell Curve. He claimedthat the debate about whether and how much genes and theenvironment have to do with ethnic differences remains unresolved.The media furore over the idea that there may be intergroupdiJferences in intelligence demonstrates the highly political nature ofthe topic.

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2,2 s Biological level of analysis: genetics and behaviour

Give me a dozen hearthy infants and my own specific worrd to bring themup in, and I'Il guarantee to take any one at random and train him tobecome any type of specialist I might select_doctor, lawer, artist,merchant, chef and yes, even beggar and thief, regardliss of his talents,penchants, tendencies, abitities, vocations, and race of his incestors.This quote from John B. Watson (Ig24) illustrares the purely"nurture" side of the debate. It is only recently that the interactionof biological and environmental factois has been considered.one of rhe difficulties in determining the origin of intelligence is thatthere has been-and continues to be-much debate about thenature of intelligence. what is it, and how can it be measured?charles Spearman, an early intenigence theorist, found that studentperformance across different subjects was positivery correrated. As aresult of this, he argued that there is a general inteligence factorthat is the basis for all intelligence-something that he called the ,,g,,factor' Modern intelligence testing attempts to assess this g, ratherthan looking at specific school subjects. Instead of testing l' student,sskill in history, mathematics, or art history, the test focuses on spatialability, reasoning, divergent rhinking, and verbal fluency. Thequestion then is: where does g come from?

Research on intelligenceBouchard and McGue (l9gr) reviewed rrr studies of Ie correlationsbetween siblings from research studies on intelligence from aroundthe world. This is what is called a meta-analysis-the statisticarsynthesis of the data from a set of comparable studies of a problemthat yields a quantitative summary of the pooled results. Tirey foundthat the closer the kinship, the higher the correlation for Ie. Inorder to investigate the role of genetics in intelligence, reselrchershave used identicar twins who have been brougit rrp ,.pu.ui.tyfrom birth. This provides researchers with participarus #ho hurr. u100 per cent genetic rerationship, but have grown up in differentenvironments' This is based on the assumption that any similaritybetween their Ies-beyond that expected by chan..__,rr, be dueto genetics rather than the environment.The Minnesota Twin Study (Bouchard et al. 1990) is alongitudinal study rhat has been going on since 1979.lnthis study,MZAs (identical twins raised apart) are compared to Mzrs (identicaltwins raised together). This is the most cross-cultural study to date,with participants from all over the world. Another advantage of this

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2,2 * B161ot1.al level of analysis: genetics and behaviourstudy is that the mean age of the MZAs was 4I years old (at the startof the study). Until this point, almost all intelligence rese4rch ontwins was carried out with adolescentsEach twin completed approximately 50 hours of testing andinterviews. The concordance rates of intelligence from the study areshown in the table below.

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Bouchard et al. determined a heritability estimate of 70 per cent-that is, tlnatTO per cent of intelligence can be attributed to geneticinheritance. This means that 30 per cent of intelligence may beattributed to other factors.Much research has supported the findings of the Minnesota TWinStudy. In addition, the size and nature of the sample has made it oneof the most impressive twin studies ever carried out. In spite of this,there are some criticisms of the study.o Bouchard relied on media coverage to recruit participants.o There are some ethical concerns about the way he reunited thetwins.o There was no adequate control to establish the frequency ofcontact between the twins prior to the study.o We cannot assume that twins who are raised together experiencethe same environment-this is called the "equal environment

assumption".One of the ways in which the final criticism has been challenged isby looking at adoption studies.In adoption studies, the intelligence of the adopted child is correlatedwith the intelligence of the adoptive parent. Since there is nobiological link between the adoptive parent and the child, theenvironmental influence should be evident.Scarr and Weinberg (1977) and Horn et aI. (1979) focused onparents who had raised both adopted and natural children. Theassumption is that all the children had the same upbringing, in thesame environment, with the same parents. Any significantdifferences between parent-child IQ correlations for adopted andnatural children should be attributable to genes. The researchersfound no significant difference in IQ correlations. This was veryinteresting, because in almost all the families in these studies, theadoptive parents were wealthy, white, and middle class, with highIQs, and the adopted children were from poor, lower-classbackgrounds, with lower-IQ parents.In other research, Wahlsten (t997) claims that well-controlledadoption studies conducted in France have found that transferringan infant from a family with a low socio-economic status to a home

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2.2 * Biological level of analysis: genetics and behaviourrs\rrrpurer\:'s:c-lt-a.\r\l:s\s-es-srlsrrr:rr:\a\r:'l:rrr:5sl:\childhood IQ scores by 12-16 points, or about one standarddeviation. This seems to suggest that intelligen'ce has a lot to do withthe environment as well as genetics. An enriched environment may

raise IQ in children. It is likely that there is a strong interactionbetween genes and the environment to produce intelligence level.Some concluding thoughts on intelligenceThere are some other things to consider when examining the geneticexplanation of intelligence. One problem, as discussed earlier, is thedefinition of intelligence. Is intelligence only based on knowledge, oris it related to our ability to solve problems? Hainer et al. (1988)carried out a PET scan study which indicated that when solving areasoning problem, individuals with a high IQ had lower metabolicrates than those with a low IQ. This difference was seen only inproblem solving, and not in data recall. This may mean that thosewith higher IQs use less energy to think than those with lower IQs.This is known as the less effort hypothesis.Plomin and Petrill (1997\ found that correlations between parentand child IQs change over time. Between the ages of 4 and 6 years,they found a 40 per cent correlation; in early adulthood it rose to 60per cenq and in older adults it was 80 per cent. They concluded thatit is possible that our genetic disposition pushes us towardsenvironments that accentuate that disposition, thus leading toincreased heritability throughout the lifespan. Socio-economic classappears to be one of the most important environmental factors inthe development of intelligence. Poverty-not genetic inferiority-iskey to understanding differences in intelligence.The Flynn effect refers to the rise of average scores on inteiligencetests in most parts of the world over the last century. James R. Flynntried to document this in order to create awareness of itsimplications. According to Ulric Neisser, who wrote an article on thephenomenon in The American Scientist in 1997, the average meanscores on standard IQ tests have been going up by about three pointsevery l0 years, and the increase is even higher in measures ofabstract-reasoning ability. The cause of these gains is unknown, butexperts discuss whether they reflect a real increase in intelligence oran increasing ability to crack intelligence tests. Other possible factorsinclude better nutrition, improved schooling, different child-rearingpractices, and the increased use of technology in modern life. In fact,Neisser thinks that living in a highly visual environment may playan important role in the rise in IQ scores.

As part of the early researdintelligence, the US andcountries began a branch ofcalled eugenics. This was theto find "good genes" and to"bette/' breeding in order tohealthier, more intelligentThe eugenics movement leimmigration restrictions anddiscrimination, founded on thethat intelligence was basegenetics alone. lt attempted toentire groups of people as "frt"inferior". ln the US, eugenicsthe sterilization of women whoconsidered "feeble-minded".centre for eugenics research wCold Springs Harbor, New Yorkthe movement failed towas that it was poverty whicha key role in poor schoolnot membership of a particulargrouP.To read more about eugenicto www.eugenicsarchiveeugenics/

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1,": utioni," --rif principle which underpins the biological level of arialysis isIr".i ,j-i environment presents challenges to each individual. This-rL : l:-i ihat those who adapt best to the environment will have a-:1'r:i:: chalce of surviving, having children, and passing on their genes'- :: offspring. This is the principle of Charles Darwin's theory of" - --Lln.." i,-', -l's theory of natural selection explains how species acquiret.ii",:.-,.'e characteristics to survive in an ever-changing environment.r,- - :.ling to the theory of natural selection, those members of ar,r --,=s n'ho have characteristics which are better suited to the' r: i ,nment will be more likely to breed, and thus to pass on theser;r , One example of this was seen by Darwin when he travelledtr : --:lapagos Islands. Finches on different islands had different-rl -ri beaks. He found that the birds on each island had the beak:u-i ,\as most advantageous for the food available in that particularIi : .:t. Over several generations, the result of natural selection isiti ::e species develops characteristics that make it more:::iiitive in its environment. This process is called adaptation.r -::- Darwin presented his theory in the book On the Origin of: ,:,:, he was not aware of the biological processes through whichr;iil : :re inherited.

rr :: jirion to arguing that traits may be handed down, Darwin also"r : ':e foundation for psychologists and biologists to study animalsr':- -:re hope of gaining insight into human behaviour. In The Descenti :-;,: r1871), Darwin noted that humans have a number ofr " -:-,itrurS in common with other animals. These include mate'r '--r-rln, love of mother for offspring, and self-preservation. He also,rr 11- -)n to catalogue a number of facial expressions that peoplet.l .:',rjth the apes. He argued that humans also share many of the,,i--,: ieelings as animals.+ i,:.' \\'Ery in which evolution is studied is by looking at ther': -.;iour of our closest relatives in the animal kingdom-primates.* r: :-in of a recent study by Professor Tetsuro Matsuzawa (2007), ofq : r University in Japan, was to examine spatial memory in youngt'":rps. The researchers took three pairs of chimps and taught them::.Lrgnize the numerals from I to 9 on a computer monitor. Bothr : :jrimps and the human participants were later seated at a:-ruier terminal, where the numerals flashed up very briefly on a- --l-screen monitor in a random sequence. The numbers werelr::- replaced with blank squares, and the participant had to':: tmber which numeral appeared in which location, and touchi:,: rquares in the appropriate sequence.*:: human participants made many errors, and their accuracyl.:::cdsed as the numbers were replaced with blank squares morei.".:.Jr'. The chimpanzees showed remarkable memory for the

':,,--al distribution of the numbers, with no difference when- -:-t-rers were shown for shorter durations. psychologists argue that' r f necessary adaptation for chimpanzees to have this type ofr':lrfrY so that they can remember where food resources-as well;: ::rgers-are in the rainforest. Perhaps as agriculture developed,

2.2 i Biological level of analysis: genetics and behaviour

Charles Danruin - the father ofevolutionary theory

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Chimpanzee testing her memory skills

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2.2 r Biological level of analysis: genetics and behaviourthis skill was no longer so essential for human survival. Humansmay have surrendered this ability in order to use their brains todevelop language. In other words, it appears that the memory skillsof both chimpanzees and humans have adapted to become mostsuitable for the respective environments in which they each live.Evolutionary psychologyEvolutionary psychology is grounded on the principle that as genesmutate, those that are advantageous are passed down through aprocess of natural selection. Evolutionary psychologists attempt toexplain how certain human behaviours are testimony to thedevelopment of our species over time. It is important to rememberthat natural selection cannot select for a behaviour; it can only selectfor mechanisms that produce behaviour.One example of evolutionary research is the study of emotions. DanFessler of the University of California at Los Angeles has carried outresearch on disgust. He argues that the emotion of disgust allowedour ancestors to survive long enough to produce offspring, who inturn passed the same sensitivities on to us. Fessler (2006)investigated the nausea experienced by women in their firsttrimester of pregnancy. During this period, an infusion of hormoneslowers the expectant mother's immune system so as not to fight thenew foreign genetic material in her womb. Fessler hypothesized thatthe nausea response helps to compensate for the suppressedimmune system. To test the theory, Fessler gathered 496 }:.ealthypregnant women between the ages of 18 and 50 years, and askedthem to consider 32 potentially stomach-turning scenarios-including walking barefoot and stepping on an earthworm, someoneaccidentally sticking a fish hook through their finger, and maggotson a piece of meat in an outdoor waste bin. Before asking thepregnant women to rank how disgusting they found these scenarios,Fessler posed a series of questions, designed to determine whetherthey were experiencing morning sickness. In keeping with Fessler'stheory, women in their first trimester scored much higher across theboard in disgust sensitivity than their counterparts in the second andthird trimesters. But when Fessler controlled the study for morningsickness, the response only held for disgusting scenarios involvingfood, such as the maggot example.According to Fessler, many of the diseases that are most dangerousare food-borne, but our ancestors could not afford to be picky aboutwhat they ate all the time. Natural selection may have helpedcompensate for the increased susceptibility to disease during thisrisky period in pregnancy, by increasing the urge to be picky aboutfood, however much additional foraging this may havb required.That the sensitivity seems to diminish as the risk of disease andinfection decreases is consistent with the view of disgust as a form ofprotection against disease.In another study, Curtis et al. (2004) carried out research on theInternet to test whether there were patterns in people's disgustresponses. They used an online survey in which participants wereshown 20 images. For each image, they were asked to rank theirlevel of disgust. Among the 20 images were seven pairs in which

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2.2 * Biological level of analysis: genetics and behaviourlme was infectious or potentially harmful to the immune system,md the other was visually similar but non-infectious-for example,rme pair was a plate of bodily fluids and a plate of blue viscousmquid. There were 77 000 participants from 165 countries. Thefudings confirmed that the disgust reaction was most stronglycfficited for those images which threaten one's immune system.hterestingly, the disgust reaction also decreased with age. As thempaph shows, disgust reactions were higher in young people than indder people. In addition, women had higher disgust reactions thanmen. Once again, this supports the idea of disgust as a key tomccessful reproduction.

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lerel of disgust sensitivity in relation to ageThe original survey can be found at \ rvyw.bbc.co.uk/science/humanbodyi mind/ surveys/ disgustIn spite of such evidence, there are some things to consider whenexamining an evolutionary argument.r Since it may be difficult to test empirically some evolution-basedtheories, researchers may be susceptible to confirmation bias-that is, they see what they expect to see.o Little is known about the behaviour of early Homo sapiens, sostatements about how humans "used to be" are hypothetical.o Evolutionary arguments often underestimate the role of culturalinfluences in shaping behaviour.Ethical considerations in research into genetic influencesof behaviourResearch in human genetics aims to identify particular genesinvolved in hereditary diseases. This kind of research may pose risksto participants because of the link between genetic heritage andpeople's life. Genetic information obtained from such research canalso be problematic for the participant's family. If misused, geneticinformation can be stigmatizing and may affect people's ability to getjobs or insurance.In any study, participants should always know how their privacyand confidentiality will be protected, and what will happen to anygenetic material or information obtained as part of the study. Theaims and procedure of the study must be explained in plain

Possible exam question:Essay question (paper 1section B)Discuss the extent to whichgenetic inheritance influencesbehaviour with reference torelevant research studies.This question uses the commandterm "discuss" which means thatyou should present a balancedview that includes a number ofarguments that address the wayin which genetic factors influencebehaviour. You should presentevidence from research and youshould arrive at a conclusionbased on the argumentspresented.

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2.2 o Biological level of analysis: genetics and behaviourlanguage and partiapants must sign an informed consent paper toshow that they have a clear understanding of the study they areparticipating in, and the implications, inchiding any potential harm.Confidentiality and privacy can be protected by coding information(where a code is assigned and only a small number of researchershave access to the codes) or by fully anonymizing the sample (whereresearchers cannot link samples or information to particular people).Anonymization protects confidentiality from insurance companies,employers, police, and others, but it also can limit the scientificvalue of the study by preventing follow up and further investigation.Genetic research can reveal unexpected information that may harmresearch participants. Examples include evidence of misattributedpaternity or unrevealed adoptions within a family. Another exampleoccurs when a person discovers from the study that he or she carriesthe gene for a particular genetic disorder. This may cause unduestress as the participant then fears the potential onset of the disorder.Some groups, including Aboriginal people, may have objections togenetic study as a cultural principle. Given the existence of otherforms of discrimination against such groups, and the history of theeugenics movement, fhis is no surprise. In such cases it is veryimportant to consult umth relevant community leaders andorganizations. Consent is a community matter for many Aboriginaland ethnic groups as well as an individual concern.