www.fgks.org   »   [go: up one dir, main page]
Wikipedia

Nature versus nurture: Difference between revisions

Browse history interactively
← Previous editNext edit →
Content deleted Content added
VisualWikitext
Tag: Reverted
additional types of determinism
(46 intermediate revisions by 24 users not shown)
Line 1:
{{Short description|Debate about heredity and environment as determinants of physical or mental development}}
[[File:The Tolmachevy Sisters, ESC2014 Meet & Greet 28 (crop).jpg|thumb|280px|In the twentieth century, studies of twins separated at birth helped provide better insight into the debate about nature versus nurture. Like identical twins who were raised together, identical twins who were reared apart from birth tend to be similar in behavioral and psychological traits.<ref>{{Cite book|last=Plomin|first=Robert|url=https://books.google.com/books?id=s7SeDwAAQBAJ&pg=PA73|title=Blueprint: How DNA Makes Us Who We Are|date=2019-07-02|publisher=MIT Press|isbn=978-0-262-53798-8|pages=73–80|language=en|author-link=Robert Plomin}}</ref>|alt=]]'''Nature versus nurture''' is a long-standing debate in biology and society about the balancerelative betweeninfluence twoon competinghuman factorsbeings whichof determine fate:their [[genetics|genetic inheritance]] (nature) and environmentthe environmental conditions of their development ([[nurture]]). The [[alliterative]] expression "nature and nurture" in English has been in use since at least the [[Elizabethan era|Elizabethan period]]<ref>In English at least since Shakespeare (''[[The Tempest]]'' 4.1: ''a born devil, on whose nature nurture can never stick'') and [[Richard Barnfield]] (''Nature and nurture once together met / The soule and shape in decent order set.''); in the 18th century used by [[Philip Yorke, 1st Earl of Hardwicke]] (''Roach v. Garvan'', "I appointed therefore the mother guardian, who is properly so by nature and nurture, where there is no testamentary guardian.")</ref> and goes back to [[medieval French]].<ref>English usage is based on a tradition going back to medieval literature, where the opposition of ''nature'' ("instinct, inclination") ''norreture'' ("culture, adopted mores") is a common motif, famously in [[Chretien de Troyes]]' ''[[Perceval, the Story of the Grail|Perceval]]'', where the hero's effort to suppress his natural impulse of compassion in favor of what he considers proper courtly behavior leads to catastrophe. ▼
{{Redirect|Nurture|the album|Nurture (album){{!}}''Nurture'' (album)}}
▲[[File:The Tolmachevy Sisters, ESC2014 Meet & Greet 28 (crop).jpg|thumb|280px|In the twentieth century, studies of twins separated at birth helped provide better insight into the debate about nature versus nurture. Like identical twins who were raised together, identical twins who were reared apart from birth tend to be similar in behavioral and psychological traits.<ref>{{Cite book|last=Plomin|first=Robert|url=https://books.google.com/books?id=s7SeDwAAQBAJ&pg=PA73|title=Blueprint: How DNA Makes Us Who We Are|date=2019-07-02|publisher=MIT Press|isbn=978-0-262-53798-8|pages=73–80|language=en|author-link=Robert Plomin}}</ref>|alt=]]'''Nature versus nurture''' is a long-standing debate in biology and society about the balance between two competing factors which determine fate: [[genetics]] (nature) and environment (nurture). The alliterative expression "nature and nurture" in English has been in use since at least the [[Elizabethan era|Elizabethan period]]<ref>In English at least since Shakespeare (''[[The Tempest]]'' 4.1: ''a born devil, on whose nature nurture can never stick'') and [[Richard Barnfield]] (''Nature and nurture once together met / The soule and shape in decent order set.''); in the 18th century used by [[Philip Yorke, 1st Earl of Hardwicke]] (''Roach v. Garvan'', "I appointed therefore the mother guardian, who is properly so by nature and nurture, where there is no testamentary guardian.")</ref> and goes back to [[medieval French]].<ref>English usage is based on a tradition going back to medieval literature, where the opposition of ''nature'' ("instinct, inclination") ''norreture'' ("culture, adopted mores") is a common motif, famously in [[Chretien de Troyes]]' ''[[Perceval, the Story of the Grail|Perceval]]'', where the hero's effort to suppress his natural impulse of compassion in favor of what he considers proper courtly behavior leads to catastrophe.
Lacy, Norris J. (1980) ''The Craft of Chrétien de Troyes: An Essay on Narrative Art'', Brill Archive, [https://archive.org/details/craftofchretiend0000lacy/page/5 p. 5].</ref>
The complementary combination of the two concepts is an ancient concept ({{lang-grc|ἁπό φύσεως καὶ εὐτροφίας}}).<ref>In [[Plato]]'s ''[[Protagoras (dialogue)|Protagoras]]'' 351b; an opposition is made by Protagoras' character between ''art'' on one hand and ''constitution and fit nurture'' (nature and nurture) of the soul on the other, ''art'' (as well as ''rage and madness''; {{Lang-grc|ἀπὸ τέχνης ἀπὸ θυμοῦ γε καὶ ἀπὸ μανίας|label=none}}) contributing to ''boldness'' ({{Lang-grc|θάρσος|label=none}}), but ''nature and nurture'' combine to contribute to ''courage'' ({{Lang-grc|ἀνδρεία|label=none}}).
Line 11 ⟶ 10:
The view that humans acquire all or almost all their behavioral traits from "nurture" was termed ''[[tabula rasa]]'' ('blank tablet, slate') by [[John Locke]] in 1690. A ''blank slate view'' (sometimes termed ''blank-slatism'') in human [[developmental psychology]], which assumes that human behavioral traits develop almost exclusively from environmental influences, was widely held during much of the 20th century. The debate between "blank-slate" denial of the influence of [[heritability]], and the view admitting both environmental and heritable traits, has often been cast in terms of nature ''versus'' nurture. These two conflicting approaches to human development were at the core of an ideological dispute over research agendas throughout the second half of the 20th century. As both "nature" and "nurture" factors were found to contribute substantially, often in an inextricable manner, such views were seen as naive or outdated by most scholars of human development by the 21st century.<ref>[[David Moore (psychologist)|Moore, David S.]] [2002] 2003. ''[[The Dependent Gene|The Dependent Gene: The Fallacy of 'Nature Vs. Nurture'<nowiki/>]]''. US: [[Henry Holt (publisher)|Henry Holt]]. {{ISBN |978-0805072808}}. {{ASIN|0805072802}}.</ref><ref>Esposito, E. A., E. L. Grigorenko, and [[Robert Sternberg|Robert J. Sternberg]]. 2011. "The Nature–Nurture Issue (an Illustration Using Behaviour-Genetic Research on Cognitive Development)." In ''An Introduction to Developmental Psychology'' (2nd ed.), edited by A. Slater and G. Bremner. [[British Psychological Society|British Psychological Society Blackwell]]. p. 85.</ref><ref>{{cite magazine|last = Dusheck|first = Jennie|date =October 2002|url = https://www.researchgate.net/publication/264487164 |title = The Interpretation of Genes|journal = [[Natural History (magazine)|Natural History]]|volume = 111|issue = 8|page = 52}}</ref><ref>Carlson, N. R. ''et al.'' 2005. ''Psychology: the science of behaviour'' (3rd Canadian ed.). [[Pearson Education|Pearson]]. {{ISBN|0-205-45769-X}}.</ref><ref>[[Matt Ridley|Ridley, M.]] 2003. ''[[Nature via Nurture: Genes, Experience, & What Makes Us Human]]''. [[HarperCollins]]. {{ISBN|0-00-200663-4}}.</ref>
 
The strong dichotomy of nature ''versus'' nurture has thus been claimed to have limited relevance in some fields of research. Close [[feedback]] loops have been found in which nature and nurture influence one another constantly, as seen in [[self-domestication]]. In [[ecology]] and [[behavioral genetics]], researchers think nurture has an essential influence on the nature of an individual.<ref>{{cite journal |author=Powledge, Tabitha M. |title=Behavioral Epigenetics: How Nurture Shapes Nature|journal=[[BioScience]] |volume=61 |issue=8 |pages=588–592 |date=August 2011 |doi=10.1525/bio.2011.61.8.4 |doi-access=free }}</ref><ref>{{cite journal |author=Normile, Dennis |title=Nature From Nurture |journal=[[Science (journal)|Science]] |volume=351 |issue=6276 |pages=908–910 |date=February 2016 |doi=10.1126/science.351.6276.908 |pmid=26917750|doi-access=free }}</ref> Similarly in other fields, the dividing line between an inherited and an acquired trait becomes unclear, as in [[epigenetics]]<ref name="Moore_2015">{{cite book|last1=Moore|first1=David S.|title=The Developing Genome: An Introduction to Behavioral Epigenetics|date=2015|publisher=Oxford University Press|isbn=9780199922345|edition=1st}}</ref> or [[Prenatal development|fetal development]].<ref>[[Timo Hannay|Hannay, Timo]]. 2014. "[http://www.edge.org/response-detail/25365 Nature Versus Nurture | What Scientific Idea is Ready for Retirement?]" ''Edge''. [[Edge Foundation, Inc.]] Retrieved 21 June 2020.</ref>
 
==History of debate==
Line 22 ⟶ 21:
|volume=048}}</ref> Though Chen was obviously negative to the question, the phrase has often been cited as an early quest to the nature versus nurture problem.<ref>李盟编,DNA密码,中国言实出版社,2012.04,第133页</ref>
 
[[John Locke]]'s ''[[An Essay Concerning Human Understanding]]'' (1690) is often cited as the foundational document of the ''[[Tabula rasa|blank slate]]'' view. In the ''Essay'', Locke specifically criticizes [[René Descartes]]'s claim of an [[innate idea]] of [[God]] that is universal to humanity. Locke's view was harshly criticized in his own time. [[Anthony Ashley-Cooper, 3rd Earl of Shaftesbury]], complained that by denying the possibility of any innate ideas, Locke "threw all order and virtue out of the world," leading to total [[moral relativism]]. By the 19th century, the predominant perspective was contrary to that of Locke's, tending to focus on "[[instinct]]." [[Leda Cosmides]] and [[John Tooby]] noted that [[William James]] (1842–1910) argued that humans have ''more'' [[instinct]]s than animals, and that greater freedom of action is the result of having more [[Psychology|psychological]] instincts, not fewer.<ref>{{cite web|url = https://www.cep.ucsb.edu/primer.html|last1 = Cosmides|first1 = Leda|last2 = Tooby|first2 = John|website = Center for Evolutionary Psychology|title = Evolutionary Psychology: A Primer|publisher = ucsb.edu|date = January 13, 1997|access-date = October 19, 2021|archive-date = February 6, 2023|archive-url = https://web.archive.org/web/20230206213533/https://www.cep.ucsb.edu/primer.html|url-status = dead}}</ref>
 
The question of "innate ideas" or "instincts" were of some importance in the discussion of [[free will]] in [[moral philosophy]]. In 18th-century philosophy, this was cast in terms of "innate ideas" establishing the presence of a universal virtue, prerequisite for objective morals. In the 20th century, this argument was in a way inverted, since some philosophers ([[J. L. Mackie]]) now argued that the evolutionary origins of human behavioral traits forces us to concede that there is no foundation for ethics, while others ([[Thomas Nagel]]) treated ethics as a field of cognitively valid statements in complete isolation from evolutionary considerations.<ref>{{cite web |url=http://www.metanexus.net/metanexus_online/show_article2.asp?ID=6008 |first=John |last=Mizonni |title=Ruse's Darwinian ethics and Moral Realism |publisher=Metanexus Institute |work=metanexus.net |url-status=dead |archive-url=https://web.archive.org/web/20061001133708/http://www.metanexus.net/metanexus_online/show_article2.asp?id=6008 |archive-date=2006-10-01 }}</ref>
 
=== Early to mid-20th century ===
In the early 20th century, there was an increased interest in the role of theone’s environment, as a reaction to the strong focus on pure heredity in the wake of the triumphal success of Darwin's [[Evolution|theory of evolution]].<ref>Craven, Hamilton. 1978. ''The Triumph of Evolution: The Heredity-Environment Controversy, 1900–1941'': "While it would be inaccurate to say that most American experimentalists concluded as the result of the general acceptance of Mendelism by 1910 or so that heredity was all powerful and environment of no consequence, it was nevertheless true that heredity occupied a much more prominent place than environment in their writings."</ref> During this time, the [[social sciences]] developed as the project of studying the influence of culture in clean isolation from questions related to "biology. [[Franz Boas]]'s ''[[The Mind of Primitive Man]]'' (1911) established a program that would dominate [[American anthropology]] for the next 15 years. In this study, he established that in any given [[population]], [[biology]], [[language]], [[Material culture|material]], and [[symbolic culture]], are [[Autonomy|autonomous]]; that each is an equally important dimension of human nature, but that none of these dimensions is reducible to another.
 
==== Purist behaviorism ====
Line 39 ⟶ 38:
 
==== Determinism ====
{{See also|Social determinism|Cultural determinism|Biological determinism|}}
At the height of the controversy, during the 1970s to 1980s, the debate was highly ideologised. In ''[[Not in Our Genes: Biology, Ideology and Human Nature]]'' (1984), [[Richard Lewontin]], [[Steven Rose]] and [[Leon Kamin]] criticise "[[genetic determinism]]" from a [[Marxist]] framework, arguing that "Science is the ultimate legitimator of bourgeois ideology ... If [[biological determinism]] is a weapon in the struggle between classes, then the universities are weapons factories, and their teaching and research faculties are the engineers, designers, and production workers." The debate thus shifted away from whether heritable traits exist to whether it was [[Politics|politically]] or [[Ethics|ethically]] permissible to admit their existence. The authors deny this, requesting that evolutionary inclinations be discarded in ethical and political discussions regardless of whether they exist or not.<ref>Kohn, A. (2008) ''The Brighter Side of Human Nature''. Basic Books. {{ISBN|078672465X}}</ref>
 
Line 55 ⟶ 54:
 
Pinker argues that all three dogmas were held onto for an extended period even in the face of evidence because they were seen as ''desirable'' in the sense that if any human trait is purely conditioned by culture, any undesired trait (such as crime or aggression) may be engineered away by purely cultural (political means). Pinker focuses on reasons he assumes were responsible for unduly repressing evidence to the contrary, notably the fear of (imagined or projected) political or ideological consequences.<ref>{{cite web |author=Pinker, Steven |url=http://pinker.wjh.harvard.edu/books/tbs/index.html |title=Steven Pinker – Books – The Blank Slate |publisher=Pinker.wjh.harvard.edu |access-date=2011-01-19 |url-status=dead |archive-url=https://web.archive.org/web/20110510091413/http://pinker.wjh.harvard.edu/books/tbs/index.html |archive-date=2011-05-10}}</ref>
 
===Political aspects===
 
With the exception of positing a genetic contribution to [[LGBT]] behavior, a nurture-only hypothesis for human traits tends to be advocated by the [[political Left]], while a combination of nature and nurture tends to favored by the [[political Right]].<ref>[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4567596/ Suhay E, Jayaratne TE. Does Biology Justify Ideology? The Politics of Genetic Attribution]. Public Opin Q. 2013 Summer;77(2):497-521. {{doi|10.1093/poq/nfs049}}. {{PMID|26379311}} {{PMCID|4567596}}</ref><ref>https://medium.com/@acflewis/gay-genes-liberals-and-the-relevance-of-biology-to-politics-b7c4c0195e61</ref>
 
==Heritability estimates==
Line 87 ⟶ 82:
== Gene–environment interaction ==
{{Main|Gene–environment interaction}}
{{rquote|right|Many properties of the brain are genetically organized, and don't depend on information coming in from the senses.|[[Steven Pinker]]}}The interactions of genes with environment, called ''gene–environment interactions'', are another component of the nature–nurture debate. A classic example of gene–environment interaction is the ability of a diet low in the amino acid [[phenylalanine]] to partially suppress the genetic disease [[phenylketonuria]]. Yet another complication to the nature–nurture debate is the existence of [[gene–environment correlation]]s. These correlations indicate that individuals with certain genotypes are more likely to find themselves in certain environments. Thus, it appears that genes can shape (the selection or creation of) environments. Even using experiments like those described above, it can be very difficult to determine convincingly the relative contribution of genes and environment. The analogy "genetics loads the gun, but environment pulls the trigger" has been attributed to [[Judith Stern]].<ref>Ramos RG, Olden K. Gene-environment interactions in the development of complex disease phenotypes. Int J Environ Res Public Health. 2008 Mar;5(1):4-11. doi: 10.3390/ijerph5010004. PMID: 18441400; PMCID: PMC3684407.</ref>
 
Heritability refers to the origins of differences between people. Individual development, even of highly heritable traits, such as eye color, depends on a range of environmental factors, from the other genes in the organism, to physical variables such as temperature, oxygen levels etc. during its development or ontogenesis.
Line 115 ⟶ 110:
An alternative to contrasting nature and nurture focuses on "[[obligate]] vs. facultative" adaptations.<ref name=Buss2011>{{cite book|last=Buss|first=D. M.|date=2011|title=Evolutionary Psychology: The New Science of the Mind|edition=4th|location=New York|publisher=[[Prentice Hall]]}}</ref> Adaptations may be generally more obligate (robust in the face of typical environmental variation) or more facultative (sensitive to typical environmental variation). For example, the rewarding sweet taste of sugar and the pain of bodily injury are obligate psychological adaptations—typical environmental variability during development does not much affect their operation.<ref>{{cite book|last=Symons|first=D.|date=1979|title=The evolution of human sexuality|url=https://archive.org/details/evolutionofhuman00dona|url-access=registration|location=Oxford|publisher=[[Oxford University Press]]|isbn=978-0-19-502535-4}}</ref>
 
On the other hand, facultative adaptations are somewhat like "if-then" statements.<ref>{{cite web|last=Lynch|first=K.|date=2013|url=http://medicalxpress.com/news/2013-12-heritability.html|title=Explainer: What is Heritability?|work=MedicalXpress.com}}</ref> An example of a facultative psychological adaptation may be adult [[attachment style]]. The attachment style of adults, (for example, a "secure attachment style," the propensity to develop close, trusting bonds with others) is proposed to be conditional on whether an individual's early childhood caregivers could be trusted to provide reliable assistance and attention. An example of a facultative physiological adaptation is tanning of skin on exposure to sunlight (to prevent skin damage). Facultative social adaptation have also been proposed. For example, whether a society is warlike or peaceful has been proposed to be conditional on how much collective threat that society is experiencing.<ref name="Fog2017">{{cite book |last1=Fog |first1=Agner |date=2017 |title=Warlike and Peaceful Societies: The Interaction of Genes and Culture |publisher=Open Book Publishers |isbn=978-1-78374-403-9 |doi=10.11647/OBP.0128 |doi-access=free }}</ref>
 
===Advanced techniques===
Line 121 ⟶ 116:
[[Quantitative research|Quantitative studies]] of heritable traits throw light on the question.
 
Developmental genetic analysis examines the effects of genes over the course of a human lifespan. Early studies of intelligence, which mostly examined young children, found that [[heritability]] measured 40–50%. Subsequent developmental genetic analyses found that variance attributable to additive environmental effects is less apparent in older individuals, with estimated heritability of IQ increasing in adulthood.<ref>{{Cite journal|last1=Plomin|first1=R.|last2=Spinath|first2=F. M.|year=2004|title=Intelligence: genetics, genes, and genomics|url=https://semanticscholar.org/paper/8be605ab07a01ceb0373a0cf8113747c5a80a16c|journal=Journal of Personality and Social Psychology|volume=86|issue=1|pages=112–129|doi=10.1037/0022-3514.86.1.112|pmid=14717631|s2cid=5734393}}</ref><ref>McGue, M.; Bouchard Jr., T. J.; Iacono, W. G. and Lykken, D. T. (1993) "Behavioral Genetics of Cognitive Ability: A Life-Span Perspective", in ''Nature, Nurture, and Psychology'', by R. Plomin & G. E. McClearn (Eds.) Washington, DC: American Psychological Association</ref><ref>{{Cite journal|last1=Plomin|first1=R.|last2=Fulker|first2=D. W.|last3=Corley|first3=R.|last4=DeFries|first4=J. C.|year=1997|title=Nature, Nurture and Cognitive Development from 1 to 16 years: A Parent–Offspring Adoption Study|journal=Psychological Science|volume=8|issue=6|pages=442–447|doi=10.1111/j.1467-9280.1997.tb00458.x|s2cid=145627094}}</ref>
 
Multivariate genetic analysis examines the genetic contribution to several traits that vary together. For example, multivariate genetic analysis has demonstrated that the genetic determinants of all specific cognitive abilities (e.g., memory, spatial reasoning, processing speed) overlap greatly, such that the genes associated with any specific cognitive ability will affect all others. Similarly, multivariate genetic analysis has found that genes that affect scholastic achievement completely overlap with the genes that affect cognitive ability.
Line 129 ⟶ 124:
For a few highly heritable traits, studies have identified loci associated with variance in that trait, for instance in some individuals with [[schizophrenia]].<ref>{{cite journal | last1 = Harrison | first1 = P. J. | last2 = Owen | first2 = M. J. | year = 2003 | title = Genes for schizophrenia? Recent findings and their pathophysiological implications | journal = Lancet | volume = 361 | issue = 9355| pages = 417–9 | doi = 10.1016/S0140-6736(03)12379-3 | pmid = 12573388 | s2cid = 16634092 }}</ref> The budding field of epigenetics has conducted research showing that hereditable conditions like schizophrenia, which have an 80% hereditability with only 10% of those who have inherited the trait actually displaying Schizophrenic traits.<ref name=":0">{{Cite journal |last1=Li |first1=Huabing |last2=Lu |first2=Qiong |last3=Xiao |first3=Enhua |last4=Li |first4=Qiuyun |last5=He |first5=Zhong |last6=Mei |first6=Xilong |date=February 2014 |title=Methamphetamine Enhances the Development of Schizophrenia in First-Degree Relatives of Patients with Schizophrenia |url=http://dx.doi.org/10.1177/070674371405900206 |journal=The Canadian Journal of Psychiatry |volume=59 |issue=2 |pages=107–113 |doi=10.1177/070674371405900206 |pmid=24881129 |pmc=4079234 |issn=0706-7437}}</ref> New research is showing that gene expression can happen in adults due to environmental stimuli. For example, people with schizophrenic gene have a genetic predisposition for this illness but the gene lays dormant in most people. However, if introduced to chronic stress or introducing some amphetamines it caused the methyl groups to stick to hippocampi histones.<ref name=":1">{{Cite journal |last=Steinberg |first=Douglas |date=October 2006 |title=Determining Nature vs. Nurture |url=http://dx.doi.org/10.1038/scientificamericanmind1006-12 |journal=Scientific American Mind |volume=17 |issue=5 |pages=12–14 |doi=10.1038/scientificamericanmind1006-12 |issn=1555-2284}}</ref>
 
== Intelligence ==
==Heritability of intelligence==▼
 
▲=== Heritability of intelligence ===
{{Main|Heritability of IQ}}
Cognitive functions have a significant genetic component. A 2015 meta-analysis of over 14 million twin pairs found that genetics explained 57% of the variability in cognitive functions.<ref>{{Cite journal|last1=Polderman|first1=Tinca J C|last2=Benyamin|first2=Beben|last3=de Leeuw|first3=Christiaan A|last4=Sullivan|first4=Patrick F|last5=van Bochoven|first5=Arjen|last6=Visscher|first6=Peter M|last7=Posthuma|first7=Danielle|date=July 2015|title=Meta-analysis of the heritability of human traits based on fifty years of twin studies|url=http://www.nature.com/articles/ng.3285|journal=Nature Genetics|language=en|volume=47|issue=7|pages=702–709|doi=10.1038/ng.3285|pmid=25985137|s2cid=205349969|issn=1061-4036}}</ref> Evidence from [[behavioral genetics|behavioral genetic]] research suggests that family environmental factors may have an effect upon childhood [[Intelligence quotient|IQ]], accounting for up to a quarter of the variance. The [[American Psychological Association]]'s report "[[Intelligence: Knowns and Unknowns]]" (1995) states that there is no doubt that normal child development requires a certain minimum level of responsible care. Here, environment is playing a role in what is believed to be fully genetic (intelligence) but it was found that severely deprived, neglectful, or abusive environments have highly negative effects on many aspects of children's intellect development. Beyond that minimum, however, the role of family experience is in serious dispute. On the other hand, by late adolescence this correlation disappears, such that adoptive siblings no longer have similar IQ scores.<ref name="Plomin2008">Plomin, R., [[John C. DeFries|J. C. DeFries]], G. E. McClearn, and P. McGuffn. 2008. ''Behavioral Genetics'' (5th ed.). New York: [[Worth Publishers]]. {{ISBN|978-1429205771}}</ref>
Line 135 ⟶ 132:
Moreover, adoption studies indicate that, by adulthood, adoptive siblings are no more similar in IQ than strangers (IQ correlation near zero), while full siblings show an IQ correlation of 0.6. Twin studies reinforce this pattern: monozygotic (identical) twins raised separately are highly similar in IQ (0.74), more so than dizygotic (fraternal) twins raised together (0.6) and much more than adoptive siblings (~0.0).<ref>{{cite journal|jstor=41465638|pmid=9549239|year=1998|last1=Bouchard|first1=T. J. Jr.|title=Genetic and environmental influences on adult intelligence and special mental abilities|journal=Human Biology|volume=70|issue=2|pages=257–79}}</ref> Recent adoption studies also found that supportive parents can have a positive effect on the development of their children.<ref>{{cite journal|doi=10.1037/0022-0663.89.2.381|title=Same-age unrelated siblings: A unique test of within-family environmental influences on IQ similarity|journal=Journal of Educational Psychology|volume=89|issue=2|pages=381–390|year=1997|last1=Segal|first1=Nancy L.}}</ref>
 
=== Environmental role on IQ ===
Other studies have focused on [[Environment and intelligence|environmental factors that may affect IQ]]. For example, research has shown that factors such as access to education, nutrition, and social support can have a significant impact on IQ. Furthermore, research has suggested that certain experiences during early childhood, such as exposure to lead or other environmental toxins, can have a negative impact on IQ.<ref>{{Cite journal |last1=Ceci |first1=Stephen J. |last2=Williams |first2=Wendy M. |date=2011-02-07 |title=Understanding current causes of women's underrepresentation in science |journal=Proceedings of the National Academy of Sciences |volume=108 |issue=8 |pages=3157–3162 |doi=10.1073/pnas.1014871108 |pmid=21300892 |pmc=3044353 |bibcode=2011PNAS..108.3157C |issn=0027-8424 |doi-access=free }}</ref>
 
Studies have consistently shown that environmental factors can have a significant impact on IQ. Access to quality education has been found to have a positive effect on IQ, with one study indicating that access to quality preschool education had a lasting impact on IQ scores up to age 35. Malnutrition in early childhood has been linked to lower IQ scores later in life, while supplementation with certain nutrients such as iron and iodine has been shown to improve IQ scores. Social support is also an important environmental factor that positively affects IQ, with one study indicating that children who received high levels of emotional support from their mothers had higher IQ scores than those who received low levels of emotional support.<ref>{{Cite journal |last1=Campbell |first1=Frances A. |last2=Pungello |first2=Elizabeth P. |last3=Miller-Johnson |first3=Shari |last4=Burchinal |first4=Margaret |last5=Ramey |first5=Craig T. |date=2001 |title=The development of cognitive and academic abilities: Growth curves from an early childhood educational experiment. |url=http://dx.doi.org/10.1037/0012-1649.37.2.231 |journal=Developmental Psychology |volume=37 |issue=2 |pages=231–242 |doi=10.1037/0012-1649.37.2.231 |pmid=11269391 |issn=1939-0599}}</ref>
 
Overall, it is clear that both nature and nurture play a role in determining IQ. While genetics may provide a foundation for intelligence, environmental factors can have a significant impact on IQ throughout a person's life. Therefore, it is important to consider both factors when discussing the role of nature vs. nurture in relation to IQ.
 
==Personality traits==
Retrieved from "https://en.wikipedia.org/wiki/Nature_versus_nurture"