# Talk:Nature versus nurture/Archive 1

## Physics and the universe being deterministic rendering this debate meaningless

This article is incomplete without mentioning that the universe may be deterministic despite quantum theory producing only probabilities and that free will may be an illusion and thus the universe being deterministic means that "nature", necessarily indistinguishable from "nurture," as all nurture would be carried out deterministically, would "win" this debate with 100% nature being responsible for all human behavior. Someone please incorporate this point into the article. Foober 10:10, 10 June 2007 (UTC)

I don't think this should be incorporated here. Perhaps you should create a separate article for that, which could then be referred to here. Crusio 10:20, 10 June 2007 (UTC)

"Much of current thinking tends to discount the notion of genetics as valid in determining subjectively qualified traits, such as intelligence or personality. "

What? This isn't true at all. The trend of the research over the last decade (especially with clones) is pointing in the opposite direction. I have to go to bed right now but I'm definitely going to neutralize this article. --mav
I have to agree. The newer version was even worse - essentially that the idea that genes determine traits isn't accepted in modern biology. I re-wrote it a bit, but perhaps we should clarify what kind of traits we are talking about. There are lots of mendelian traits out there, but intelligence (the bit elephant in the room) isn't one. We can be clear about that! --Xanthoptica (talk) 17:29, 17 March 2008 (UTC)

I've been reading about this lately. Popular thinking is very much soaking up all the "gay gene!", "cancer gene!", "alcoholic gene!" headlines, but while genes can give a predisposition to things such as heart disease, they're not a map of the future. There's been recent research into the intelligence of young children that found that children of middle-class families were smarter than their working class counterparts at a very young age (something like 2 years IIRC). This was not attributed to genes, but rather the environment they grow up in. -- Tarquin 13:41 Jan 2, 2003 (UTC)

I'm not suggesting genes are always deterministic (severe genetic illnesses and some other cases are, however). Nothing happens in a vacuum and that includes the biochemical environment of the body - especially during childhood development.
Genes are analogous to blueprints for buildings in lightly regulated countries: Just because the blueprint says an electrical circuit follows a certain path, doesn't mean that the actual electrical circuit will follow that path. There might have been environmental factors that necessitated that the circuit take a different route or for it not to have been built at all due to a lack of available materials (or maybe even made of different kinds of materials not called for in the blueprint).
You cannot also lump all genes into the same bucket: Some things, like the presence of the genetic flaw that causes Huntington's disease, means a nearly 100% chance of getting that disease (nature wins the debate here). Most things, like height, are more plastic: Everyone has a relatively narrow maximum height range that their genes will naturally allow but due to disease, other illnesses, improper nutrition and not enough or the wrong type of exercise most people do not attain this height range (nature and nurture are both needed).
So different genes will influence the expression of traits in different ways. Actually it is more correct to say that the biochemical, nurturing and social environments influence the expression of different genes in different ways. These are often expressed as genetic susceptibilities to acquiring different traits (that is, they need an environmental trigger).
For example, about 10% of all cancers can be blamed on inherited genes but most cancers, even the ones from inherited genes, are triggered by environmental factors; such as diet, exercise, exposure to carcinogens and also chance mistakes in mitosis. Inherited "cancer genes" most often just give a person a greater chance of getting a certain type of cancer. The picture is very complex and isn't at all black and white (like the title of this page and the popular notion about the debate tend to imply). --mav
You're right, but we must be wary to counter the popular interpretations of the above. Extreme Raelian-style view: if we cloned Hitler's DNA, it would be Hitler himself. Easy political cop-out: criminals / the uneducated / etc are like that because it's the way they were born, rather than because of problems in society. -- Tarquin 11:14 Jan 8, 2003 (UTC)
Is this really the Raelian perspective? While many seem to take this to be the Raelian perspective, I was under the impression that their cloning project involved not only biological cloning but also a "mind tranfer" (a.k.a. "full body transplant") procedure. I think the Raelians might claim that if an appropriate "mind recording" of Hitler's couldn't be found (presumibly outside the DNA), they wouldn't be able to reincarnate him. Of course, this alternative may not be altogether plausible, and there may also not be a unified "Raelian perspective" on this. --Ryguasu
If we reject "the easy political cop-out" and instead believe "criminals / the uneducated / etc are like that because [...] of problems in society," that would seem to imply that any one of us could have ended up as, say, a criminal if subjected to some appropriate mix of "problems in society." This raises some obvious questions for each of us:
• What specific problems in society could have turned you (the reader) into, say, a murderer? An arsonist? A rapist? A pedophile? An embezzler? A litterbug? Can you see yourself becoming any of those things under any set of circumstances? Note what this implies: if you happen to find those behaviors offensive now, thus motivating you to refrain from indulging in them, then some sort of exposure to problems in society would supposedly have caused you to enjoy them instead. (Criminals get a thrill from committing crimes, so how do problems in society make crime fun?)
• Why are there different types of criminals in the "same" society? Were each of them shaped by different degrees of exposure to problems in society?
• Would different mixes of problems in society have been required to turn you into different types of criminal? If so, what are those mixes?
• Would the same mixes of problems in society have had the same effects on other people? For example, is there some mix of problems in society that could turn everyone into a pedophile?
• The definition of "criminal" varies with time and place. In societies which define homosexual behavior as a crime, for example, what "problems" in those societies cause some people to become homosexuals? Does legalizing homosexuality effectively "solve" those "problems"?
• What problems in society caused Kenneth Lay to defraud stockholders of billions of dollars, and how can we correct those problems?
• If problems in society result from people who are themselves flawed through prior exposure to problematic societies, how can a problematic society bootstrap itself into something better? It seems we have to ask someone to shrug off society's problems and behave differently than he or she has been socially programmed to behave. That would actually be an appeal to nature: someone must have the innate ability to rise above the flawed environment, and repair it for those who cannot. Teratornis 18:04, 14 November 2006 (UTC)

A few points are worth clarifying about "nature" and "nurture". First, "nature" does not reduce to anything as simple as "present at birth". Height is thought to depend very extensively on genetics, for example, but one is not born adult-sized; one must slowly grow up.

The problem is clear in the example: height certainly does manifest itself over time as one ages. But insofar as height has a "natural" component, it is' present at birth in the genome. It is just that whatever genes code for height do not manifest themselves immediately. But they are there at birth.

The real problem with using height as an example of something that is "nature" but not immediately manifest at birth is that height is of course determined by "nature" and "nurture," or, if you prefer, genes and environment. this is the whole point of Boas's important studies on height; height is clearly highly heritable, but children of immigrants to the US had much higher average adult heights than their parents, presumably because of better nutrition in the US.

I believe nature is best understood as things that are indeed innate (present at birth) as long as we recognize that things that are present at birth genetically may manifest themselves over time. How else are we to distinguish a physical feature like height (that heritable part of it) from physical features like scars -- which appear later in life and do mark the body noticably, but which are clearly not "natural?" Slrubenstein

It certainly isnt well written. To write about the differences between genes influence on height versus activity, or other influences, (self-esteem? smoking?)would require at least another sentence. ;>)---Sv

Well, unless you are a Lamarckian, I think you would have to add at least one sentence -- and cut the second sentence. Slrubenstein

Removing another problematic paragraph:

Nature versus nurture is thus, a very simplified term for explaining such debates that are more accurately stated as this: Of man's 'understanding' of the natural world; to what degree do free will and other traits of artifice conflict with the natural world to bear upon varied aspects of man's development.

I don't see much "accuracy" in this paragraph. Specific trouble spots:

1. Why speak of the "natural world"? The question is about "man" himself.
2. Why speak of "free will"? Oftentimes nature versus nurture debates are entirely about genes versus, say, parenting, with no room left over for free will. These debates may be misleading, but it is also misleading to imply that "nature versus nurture" needs to have anything to do with free will. This article should discuss free will somehow, but this is not the way.
3. What are "traits of artifice"? (I do not understand the reference here at all.)
4. Why imply a "conflict"? I'm sure there's someone out there who would describe the same phenomenon as a "harmonious interaction", or some such.

--Ryguasu

You miss the point completely, sometimes, dont you Ryg;) But the statement was brief and any confusion was to be expected. I wrote it after thinking about the nature of the NVN debate as being really just a misnomer - for what, you say?

Simple - at whatever stage of science man is at, his understanding of natural phenomenae is not complete and as such, most specific attempts to tie cause and effect are mistated - at two points in the argument:

• The first mistake is to assume a knowledge of a natural phenomenon, well enough to compare it to an effect. this isnt to say the science of finding specific links between these, isnt valid.
• Two: the aspect of or assumption of a disharmony with nature. The old idea of 'man mastering nature' rears its ugly head often enough, and it still finds its way into the premises of many of these discussions. My paragraph was an attempt to generalise the topic, to make it more valid, and further extend to those arguments within this sphere of both valid logic, and their flawed counterparts.

---Sv

I admit that the relationship between "man" and "nature" is an interesting and complex question, though I am less clear on how this readily applies to "nature versus nurture". If "nature versus nurture" frames a conflict, it does so not between "nature" and "man", but between the organism's "nature", on one hand, and the situation in which the organism grows and develops, on the other. Thus I fail to see how any of this is a subtopic of "man mastering nature", or why the latter applies to this particular article.

As for your first point, if you wish me to understand it, you'll need to clarify your vocabulary; I have no idea what you mean by "knowledge of a natural phenomenon, well enough to compare it to an effect." In particular, I don't understand the nature of or motivation for making a distinction between "natural phenomena" and "effects", or what it would mean to "compare" the one to the other. Perhaps I would understand if I'd read some of the authors that have influenced you? --Ryguasu

sigh. ill work on it. dont have time now. manana..-Sv

I've reordered everything and added some section headings, in hopes that this may make it easier to make the article less redundant and more coherent. Comments are of course welcome.

Also removing this for now:

Over the course of scientific development, the nature versus nurture debate has long been a bellweather indicator of the validity of the scientific method at the time

If this is true, it should be trivial to specify how I would measure the perceived validity of the scientific method given whether people in a given time and place were more in the "nature" camp or the "nurture" camp. It is not obvious to me how this it would done. (It's also not obvious how you easily measure whether people are leaning more towards nature or more towards nurture.)

and as might be expected, the history of science and sociology have long been intertwined.

This may well be the case, but I think it's the subject for another article. --Ryguasu

Though,in your defense, NVN is really just a euphemistic misnomer for a discussion which carries far too much pretense and assumption in it anyway. Your edits seem to be on the right track toward rendering this article less a reflection of active discussion and more a record of some past confusion. Excellent work.;) -Sv

Sv, I agree that this article is far from ideal. But are you saying an article called "nature versus nurture" cannot possibly be fruitful in any sense? If so, please make a case for its deletion. If not, please either make explicit, constructive comments (say, indicating how I am systematically removing "active discussion" - apparently a good thing - from the article) or stay out of this. Vague expressions of pessimism aren't going to help anyone. --Ryguasu

"excellent work" = pessimistic. hmm. --Sv

issue_ comment_ Shaj Miah discuss_variable_ Nature Vs. Nurture

static_ Personal Insight; FROM Physical, Emotional-Intellectual && Spiritual entitiy. temp_restruct_issue_ "Nature AND Nurture". -non vs.

point_ Nurture couldn't have taken a place without Nature_we would even exist right now to even speak && Nature couldn't have taken a place without Nurtures Consciousness.

Subject_ (Mulfunctions, Inheritance, Infections, Accidents, Inhalation- environment, Pesonal/Social Attitude-psycology, mentality/State of Mind Development)

Desease is an internal malfunction. I couldn't say much about it; possible millions of ways of why, when or how it could have occured. It also depends on genes; injury, food comsumtion && psycological conditions that may interrupt basic gene state development/adaptation interrupt.

Food is power. Bangladesh is a place where food isn't properly distributed; therefore why people die from mal-nutrition. Most people are happy with minimal things && live a good life without any major complaints or fuss. Having an open heart helps. Being cold, harsh, mean, doesnt help personal development -that goes against personal grain. Love helps everything; it may cure major psycological issues.

There's no such thing as gay genes. You may know that you may have gays in the family; but that's just knowing and believing. Gaism is inherited from ancient culture, sexual abuse, verbal abuse and other supressions. Where an indivual may dig in and justify it from history. Who wouldn't want a male figure to be dominent. We're a social icon of getting things straight; where we are phycally, mentally and emotionally strong. Overtime; it becomes a mentality of gays who are unble to intake social motor functions to function with others or find it boring, silly from disgust. You may call it rebel or being normal in culture.

Addiction may be inherited; then again it depends on what you were taught; or personaly believed and proceeded. I'd say don't preassue youself with anything that isn't an issue. Remember, alcohol was illigal. Now it being free; you have to make your own choice. It's up to a person to control themselves. They may experience withdrawl; at that time it may be good to get into sports, track, drawing, writing and other means of self expression.

Childhood Development is the most important part of the root of the mind. You may always change your ways; cut denial; accept and adapt; when you feel comfort; you may proceed. One bear step at a time for grizzleys. User:Unixmiah

Hey, Unixmiah - do you always throw around your school papers like this? You should at least put your name under it, in the form of -- ~~~~ . And frankly, those parts of the essay that are not trivial are very much improvable - your assumptions about gay people for example are hardly based on any facts, are they? Anyway, next time you want to make a contribution, a) do bother not just to copy your school essays, but come to the point relevant to the article, and b) sign your entries. -- AlexR 15:51, 27 Apr 2005 (UTC)

i dont believe in nature. genenics determine our makeup not our life does not mean it cant be changed. how we look, from head to toe may be determined by genetics but genetics are being altered daily. some animals grow faster today than 80 years ago. such as chickens which has been modified to satisfy demand. so nature is nurture. its pure systems, as long as the system maintains certain rules, it stays the same. same as in maintained. for example- people become fat if they eat loads of fatty foods and do no excercise. if they ate a healthy diet and worked out, they are likely to be slim. this is my opinion, fact or not does not matter to me because both nature and nurture are theories in their nature. why school teaches it is by far a waste of time and such as many other theories taught. user:{realcooldude2004}

## interactional

maybe we don't want to offer "interactional" as a category under the uncomplicated cases section. the title "interactional" is not quite right--everything is interactional--and the cases listed are far from uncomplicated. --Rikurzhen 05:06, 11 November 2005 (UTC)

Where does it say the interactional traits are "uncomplicated"? If anything, exactly the opposite is suggested. That is, the uncomplicated cases are the 99.9+% genetically determined or 99.9+% environmentally determined traits (I know 99.9 <= 100; but it's close enough to illustrate the concept). Those in the middle column are almost by definition "complicated". It's really important not to bring false bio-reductionist mystification over into this article, as it appears in certain others. This is not the place for some long an irrelevant digression on the nature and measure of heritability. Lulu of the Lotus-Eaters 05:31, 11 November 2005 (UTC)
the title of that section is Uncomplicated cases. --Rikurzhen 05:34, 11 November 2005 (UTC)

also, AFAIK, height and skin color show >90% heritability. --Rikurzhen 06:29, 11 November 2005 (UTC)

## Language Learning

The section on a child being able to learn every language equally requires some qualification which I'll add in later. Dyslexia and other disorders interfere with some languages more than others, and the pattern can be significant. Language learning generally involves a spoken and written component and a dyslexic who has difficulty with Chinese may be fine with English and vice-versa. It's not a big beef but later I'll insert a comment on how people without notable language impairment should be able to learn any language equally. --Davril2020 16:59, 26 December 2005 (UTC)

This an interesting point, though probably a clause or two of caveats is enough to make the point. My wild guess is that tonal languages would present special problems for people with some types of hearing disorders also (and perhaps vocal disorders). But I'm no psycholinguists, so I could be wrong. If you can find an external citation where the relation of language-specific learning is connected with genetic disorders, that would be helpful in the addition. Lulu of the Lotus-Eaters 21:46, 26 December 2005 (UTC)

It would be nice to see subsections to the Advanced techniques part, with a paragraph on calculating hertiability (and the importance of unique environmental variance), another for allelic association studies, another for quantitative trait loci mapping etc. Maybe Advanced techniques would be better titled something like Modern techniques... Pete.Hurd 01:59, 15 January 2006 (UTC)

## That table

Hey Lulu, and everyone else. Now that I look over that table some more, I like it less. Eye colour is highly heritable, with estimates ranging from .80 (Brauer & Chopra 1978 Anthropol Anz 36:109-120) to .99 (Zhu et al 2004 Twin Res 7:197-210; Posthuma et al 2005 Behav Genet DOI:10.1007/s10519-005-9007-x), but that doesn't mean that MZ twins are always concordant for eyecolour. At the other end of the table, while choice of which religion to follow is "environmental", attitudes towards organized religion show decently large heritabilities (Olson et al. 2001 J pers Soci Psych. 80:845-860). I think that table really over-simplifies issues, those triats might better be discussed rather than treated as slapped up there as pat answers. What do you think? Pete.Hurd 21:24, 27 January 2006 (UTC)

Hmmm... I'm highly suspect of Olsen there; but I haven't read the article, so I suppose I'm talking out my ass. :-). Still, it seems like it just must be confounding the obvious prevelance of correlation between genes and family environment (y'know most kids are raised in their biological parents' homes; MZ-ophilia to the side, I don't really believe researchers have often fully separated the effects). Dunno about eye color. It's just such a text book example of Mendelian recessive traits and all; but that's the whole of my knowledge of the developmental pathways of eye color.
Somewhere I have a MZ adoption study demonstrating closer similarities between MZ twins adopted apart than adopted together. Suggesting that MZ twin differences become exaggerated through contrast when raised together. There are a litany of problems with pretty much every method of estimating heritability for human traits, but I think they just make the exact number ambiguous, rather than making things which aren't heritable appear to be so... Pete.Hurd 23:04, 27 January 2006 (UTC)
However, in more general defense of the table, I think it makes a bit of a point, despite the obvious simplification. Laypeople reading about a trait are so often inclined to ask whether it is "genetic" or "environmental"; and their ontological conception really just has those two categories. Even when most people hear of some trait that is so-called "50% genetic", they almost always think of it as an additive relationship: i.e. you get two "IQ buckets" of equal size, one "environment" and one "genes", and each may be filled to varying degrees. Obviously, Norms of reaction presents a more nuanced (and more correct) picture.
Of course, even the traits in the far columns are "interactional" in some basic sense. Without an environment, a person doesn't have blood or eyes at all. So maybe the labels could be enhanced to specify, e.g. "(>99% heritability)"; "(<1% heritability)". But the idea I was trying to get across is that the traits that are not significantly interactional are special outliers. So putting something like "skin color" in the interactional column, despite most people thinking of it as a "genetic" trait helps show that even traits with significant genetic contributions are usually also substantially shaped by environmental factors. In the example there, a simple case is that light skinned people (especially) vary in skin tone hugely in relation to exposure to sunlight.
Yeah, but I think the table here understates your case. The traits which truly belong in the >99% whatever columns are really such special cases that many of the examples provided are far more interactional. Choice of language, and choice of religion are good cases (if the "which one" angle is made clear enough so that FOXP2 & heritable religiosity are ruled out), but the examples of complete genetic effects is even harder to make, which I think makes your point all the stronger: "GxE interaction is so important and pervasize that even these examples...". Pete.Hurd 23:04, 27 January 2006 (UTC)
I think it's easy for people who actually do understand what heritability is to forget just how badly most people understand what it means. My goal with the table is to try to clarify the terms, albeit in simplified form. Not in any original-researchy sense... these are well understood consensus terms among scientists. But there is a certain pedagogical requirement that goes beyond mere reporting. Lulu of the Lotus-Eaters 21:44, 27 January 2006 (UTC)
Hey Lulu, I just sent you a copy of the Olson et al paper. Your points are well taken. I'd be hugely more happy with column titles of "largely" rather than "entirely" in the end columns. You know, more shades of grey, less black & white. I think that would get across the point that there's an underlying continuum. The traits which are canonical examples of the far ends of the scale are not *really at* the far ends of the scale. Even idential twins raised together sometimes don't have the same eye colour, even without completely hostile environmental effects... Cheers, Pete.Hurd 22:25, 27 January 2006 (UTC)
Whups, just read your reply more carefully, ignore my stuff above, I'll think a bit more. Pete.Hurd 22:26, 27 January 2006 (UTC)
Thanks for the Olson paper. It was a very pleasant surprise for me, much more nuanced than I might have expected. But then, I think the authors are social psychologists rather than cognitive psychologists or behavioral geneticists, which probably accounts for that subtlety. :-). The religion issue is actually more just a cite to Waller (1990; Psychological Science 1:138-142). But I actually found some of their analogies in the intro about the need for an interactional picture to be prett good (there's one about "asking whether a leaky basement is caused more by the crack in the foundation or the water outside"). The factor analysis is rather amusing, especially their attempts to assign good descriptive names to the components (#9 = Attitudes Towards Sweets and Games was particularly entertaining, but they admit it's difficult to interpret). Still, in terms of the crude point the table is trying to make, I'm not sure how we might use all the mathematical mechanisms of Olsen or similar. Lulu of the Lotus-Eaters 07:20, 28 January 2006 (UTC)

As someone who has very recently been re-labelled from "biologist" to "psychologist" and is just catching on to the taxonomy of psychologists let me say, "social psycologists" is a way more restrictive term than I had thought. I like social psychologists, some of my best friends are social psychologists, and not that there's anything wrong with that ;-) these folks lie far outside that realm. Vernon has done some really nice stuff on the heritability of different forms of aggression.

Oh... I didn't look up the authors, I just noticed it was published in Journal of Personality and Social Psychology. I guess they let "foreigners" publish there sometimes. Lulu of the Lotus-Eaters 18:45, 28 January 2006 (UTC)

### Explaining heritability

I have some figures (copyrighted unfortunately, scanned from a textbook) that I use in class as part of the intuitive explanation of the math behind heritability. I'll send you copies and see if you think it's worth the effort of making new versions of for WP. Pete.Hurd 09:27, 28 January 2006 (UTC)

I've re-worked one of those figures (how much re-working is required on data figures to clear copyright infringment on the original?). I'm thinking that a second figure, showing graphically the effects discussed below on one trait alone (spatial reasoning or scholastic achievement would be good candidates) might make it all the more clear, but at the risk of enforcing the "two buckets" view.

Heritability for nine psychological traits as estimated from twin studies. All sources are twins raised together (sample size shown inside bars). Identical twins (MZ twins) are twice as genetically similar as fraternal twins (DZ twins) and so heritability is approximately twice the difference in correlation between MZ and DZ twins. Unique environmental variance is reflected by the degree to which identical twins raised together are dissimilar, and is approximated by 1-MZ correlation. The effect of shared environment contributes to similarity in all cases and is approximated by the DZ correlation minus the difference between MZ and DZ correlations.

Cheers, Pete.Hurd 18:46, 28 January 2006 (UTC)

### Explaining heritability (hypothetical graph)

I'm thinking that something similar to this, but that included adopted siblings as well would be even better to illustrate the concept. We would need to invent the hypothetical traits and numbers, but that doesn't seem bad necessarily, as long as we're clear that we're illustrating a concept rather than presenting a specific empirical result.

This chart illustrates three patterns one might see when studying the influence of genes and environment on traits in individuals. Trait A shows a high sibling correlation, but little heritability (i.e. high shared environmental variance c2; low heritability h2). Trait B shows a high heritability since correlation of trait rises sharply with degree of genetic similarity. Trait C shows low heritibility, but also low correlations generally; this means Trait C has a high nonshared environmental variance e2. In other words, the degree to which individuals display Trait C has little to do with either genes or broadly predictable environmental factors—roughly, the outcome approaches random for an individual. Notice also that even identical twins raised in a common family rarely show 100% trait correlation, meaning roughly that neither "nature" nor "nurture" determines everything about an individual.

Trait A (whatever it is) shows a high sibling correlation, but little heritability (M/D/A are close to each other). Trait B shows a high heritability, with strong MZ correlation, middling DZ correlation, and weak adoptive correlation. Trait C shows a slight heritability, but little sibling correlation to start with (i.e. mostly individual environmental different and/or random variation). These patterns are purely stipulated, but then, fixating readers on one particular correlation in one particular study doesn't enhance the conceptual point anyway. Lulu of the Lotus-Eaters 21:02, 28 January 2006 (UTC)

Nice idea. For the mathematically inclined, perhaps you could mention the three variables be measured there. I think they're h^2, c^2, and e^2(???), where Trait A has very high c^2, Trait B has very high h^2, and Trait C has very high e^2, and h^2+c^2+e^2=1. (Double check me on that.) --Rikurzhen 21:10, 28 January 2006 (UTC)
Yeah, this much like what I was thinking. e^2 is between the top of the M bar & 1.0, 1/2 h^2 is between the top of the D and M bars, c^2 is from 0.0 to 1/2 h^2 below the top of the D bar. I'm mildly (really only mildly, very mildly) against putting the A bars on the same graphs because they are unnecessary (which can only increase confusion) and may make it look like adoption studies and twin studies are't distinct methodologies. Adoption examples might be fun to add as well (my vote would be for O'Connor, et al. (2000) Are associations between parental divorce and children's adjustment genetically mediated? An adoption study. Dev. Psych. 36:429-437. FWIW I've got a bunch of MZ DZ & adoption graphs pilfered from various sources for general intelligence measures (mostly dealing with increasing h^2 estimates as subjects age), should real data be tempting (inheritance of intelligence is a tarpit of controversy that may be best avoided in a pedagogical example...). Pete.Hurd 21:38, 28 January 2006 (UTC)
The reason I like M/D/A all together is because it lets a reader see all the conceptual cases. Obviously, methodologies are different between adoption and MZ/DZ studies; but readers here aren't going to design studies based on what we present. Actually, D is the extraneous bar, if anything, since M and A show "as much" and "as little" genetic similarity as possible (with D just in the middle). I guess D helps in distinguishing additive (a^2) and nonadditive (d^2) genetic variance, but that's a bit over my head (and probably that of readers). Still, seeing that intermediate genetic similarity puts the bar somewhere between the height of M and A seems illustrative. Another nice thing a chart like this helps illustrate is the nonshared environment (e^2) or random variation. That is: even MZ twins raised in the same family (broad environment) show less than 100% correlations, which is a nice anti-reductive point. Lulu of the Lotus-Eaters 21:49, 28 January 2006 (UTC)

exactly, that 1-MZ is a really powerful point, MZ!=1 even for eye colour... points all well taken Pete.Hurd 22:31, 28 January 2006 (UTC)

## Table alternatives

Hey Lulu, I've been thinking about a nice graphical way to distinguish the "two buckets" view from true enlightenment, and I havn't gotten very far. The following two figures sort of get a bit of the intuitive feel cross, I think, but I'm not super happy with them...

Fig. 1 - The "two buckets" view of heritability.
Fig. 2 - The more correct "homogenous mudpie" view of heritability.

There's been some progress lately on fixing heritability, and User:Samsara might be a good person to ask for input on this as well. I'll ask him if he has time to help. Pete.Hurd 06:12, 28 January 2006 (UTC)

Hmmm... I like the pretty pictures, and I get what they're trying to say. I'm not certain whether they would convey the idea to an unfamilar reader. But if they acted as a touchstone for a few sentences of explanatory text, that just might do it. Not necessarily instead of the table (but maybe), but possibly as an adjunct. Lulu of the Lotus-Eaters 07:23, 28 January 2006 (UTC)
Yeah, a more nuanced table would work better than the pictures... Pete.Hurd 08:55, 28 January 2006 (UTC)

## fyi - Judith Rich Harris' hypothesis regarding e^2

The WP article on Judith Rich Harris is a stub and no article has been written about her book The Nurture Assumption[1], but you might want to keep her "Group Socialization Theory" in mind when crafting descriptions about the meaning of nontrivial e^2 and low c^2 in this article:

• "Strong claim: parents don't matter, development is all about peer groups"
• "Weak claim: peer groups have a strong influence on development"

--Rikurzhen 03:53, 29 January 2006 (UTC)

Do you think I characterized e^2 badly in the caption, if Harris is right? I actually don't mean the example to show family dynamics per se. That is, in my imaginary results, I think of the siblings as going to the same school and so on as well (and eating the same food, watching the same TV, whatever; at least at a general level).
What I suspect happens to a certain extent is the social interactions have some structural "roles" associated with them. So siblings might often fall into, e.g. leader/follower roles, even MZ twins raised together; and from those assumed roles, lots of other traits fall out. But it's not that one necessarily had any particular predisposition to the "leader" role, but rather the social dynamics pushes for there to be only one occupant of the role. Of course, this is my own speculation (i.e. "original research"), so I'm not going to put anything like that in the article. Lulu of the Lotus-Eaters 04:05, 29 January 2006 (UTC)
I haven't looked closely enough, I just wanted to bring it to your attention. Another hypothesis is that e^2 is the sum of a great many unique events of small effect, both biological and social (i.e., chance). --Rikurzhen 04:58, 29 January 2006 (UTC)
Looking much better, a couple of thoughts on first pass.
1. The womb experiences: there's a really nifty study demonstrating womb effects in mice (Francis et al 2003, Nature Neuroscience 6:445-446) that I intend on adding to the gene-environment interaction page. I'll send you a copy Lulu.
2. The Judith Rich Harris page really needs work! There's a great mini-bio of her in Ridley's Nature via nurture. My copy seems to be constantly out on loan...
3. I still think the end column titles need to be changed from "Entriely", I'll have a go at small copy edits soon. Go ahead & change it back if you don't like.
Absolutely, please change the column titles as you think best. Lulu of the Lotus-Eaters
4. The "bucket" v "mudpie" captions will have to be changed to something more correct...
5. The three bar graph is very nice, and the text accompanying it is too! The one thing I would add is that the heritability measure is sensitive to the environment (this is the major point to the gene-environment interaction page. The heritabilities shown for traits A, B & C might all be true for the same trait, in populations with the same genetic composition, but with different environments (see "bright" v "dull" rat line example in gene-environment interaction. I realize this is adding another level of complexity on the subject, but I don't see any reason not to mess their heads up with the truth... ...or maybe just handwave at the issue & direct them over to gene-environment interaction.
Yeah, good point about the different environments (or environmental ranges) affecting heritability. It's worth including, but probably something outside the caption itself, which might already be longer than a caption should be. Maybe make that point near your nice bucket/mudpie graphs? Dunno where it would best fit. Lulu of the Lotus-Eaters 06:18, 29 January 2006 (UTC)
Again, nicely done Pete.Hurd 05:47, 29 January 2006 (UTC)

## the "misc" section

The "Misc" section looks delete-able to me... Pete.Hurd 06:03, 30 January 2006 (UTC)

I don't know if this has been addressed, but in the table displaying a list of entirely nature versus enirely nurtured traits, there are no citations.

I don't know if you're aware, but the opening statement is the exact same as the beginning paragraph to this article at Answers.com (I don't know who copied who, but I'd suggest rephrasing?)

Answers.com frequently copies material from Wikipedia (which is entirely appropriate and legal, BTW). Far from being a reason to change WP's content, we should be flattered that it is syndicated other places (and even if we changed it, the change would simply propogate to the syndicators on whatever schedule they use). Similarly (but an unrelated topic), I notice http://www.answers.com/multiple%20dispatch has a lot of words that I wrote (for Wikipedia). Of course, articles can and do change when editors find better ways of writing things, that's the whole gestalt of WP. Lulu of the Lotus-Eaters 20:35, 5 April 2006 (UTC)

## Invention

"[These interactional traits are, in a sense, "complexly determined"]"- This a mere word invention, (What If I want to call it "not-completely determined")- I will remove, it's not properly objective. —Preceding unsigned comment added by 206.248.97.99 (talkcontribs)

ummm, so you mean it's neologism? and therefore not "objective"? I think it's a reference to the concept of "complex traits" which is definately not a neologism. Even so, the sense is clear. Not "objective" doesn't really make a whole lot of sense to me here. BTW, I noticed you changed "environmental" to "enviromental" in the Free will article, which I also don't understand, seems more of a neologism to me. Pete.Hurd 21:09, 6 August 2006 (UTC)

## Another thing on advanced techniques

That thing about being influenced by genes determing a person's intelligence by 80% makes absolutely no sense. The article doesn't even source it and defies logic. It's proven that there's a point in someone's life, usually from 11-13, that, in a sense, a person's brain hardens, where all the basic and integral parts of a person's psyche are most ingrained. Not to say that their psyche can't be affected throughout their life, but that bit about 80% is insanity. How could heritability studies tell how genes from thier parents could pop up so much later? How could genes really pop up that much later? It's an impossibility, that bit should be removed. I've studied heritability extensively and that part is plain junk. —Preceding unsigned comment added by 67.188.196.153 (talkcontribs)

"I've studied heritability extensively and that part is plain junk" really? It's odd that you havn't heard of this effect before, it's first-year psych textbook material, very far from an obscure result. You should consider providing references for sentences like "It's proven that there's a point in someone's life, usually from 11-13, that, in a sense, a person's brain hardens" Pete.Hurd 04:56, 4 September 2006 (UTC)

Alright, here's where I got the thing about solidification: http://www.huppi.com/kangaroo/L-intervention.htm

I really don't agree with a whole lot of that site but could you please explain to me how traits could pop up late into adulthood and go as high as 80%? Please, explain. This would mean that a person's intellectual development and psyche would change drastically only in the early years of adulthood. Oh wait.... I think I misunderstood it. Is this reffering to the idea that the genetic contribution of intelligence to a person's descendents is about 80% of the parent's intelligence at adulthood? That would actually make sense, I think the article should clarify that too. I guess I mistook it for biological determinism, sorry. —Preceding unsigned comment added by 67.188.196.153 (talkcontribs)

The prevailing wisdom is that heritability increases over time, not so much because genes exert stronger effect over time (see DeFries et al's textbook Behavioral Genetics # ISBN: 0716751593, for a good summary of the different stages of development and studies of same/different gene expression at transitions), but because the influence of environmental factors becomes less important as we mature and have greater ability to shape our environment (instead of our environment shaping us, which is easier for it to do when we are younger). Think of it this way: If, the older we get the more we are free to express our true selves, then if "our true selves" has a strong heritable component, then it makes sense that heritabilty should go up the older the subjects are. This seems to be what the empirical data shows. Pete.Hurd 21:22, 4 September 2006 (UTC)

Oh! Yeah, I get it now, thanks for clarifying.

Wait, actually, I have another question- does this also indicate the idea that a person with this heritability level of 80%, will produce offspring with 80% of their intelligence determined by the parent or what?

No, not quite. Heritability of 0.8 means that 80% of the population variance in the phenotype is due to genetic variance (with a bunch of ifs,ands & buts, to do with consistant environment and gene-environment interaction etc.). It's approximately, the proportion of the difference between individuals that can be ascribed to genetic differences between individuals, in a particular population, for a particular set of environmental conditions, on average. Pete.Hurd 05:43, 7 September 2006 (UTC)

Oh, I see. I think that's something that should be revised in the article, because the current version is rather vague and might make some people think similarly to my first conclusion or my recent question.

Wait, I still don't get what you mean there. Does what you say refer to what I said about a person's offspring having 80% of their intelligence determined by their parent's genetics?

Uh, hello?

Ok, going in accordance with this, I have one, last question:

Is a person's intelligence, on average, determined 50% by genes and 50% by environment, or what? Also, do the environmental gains on a person's IQ translate into heritable IQ?

Ummm, I'm not quite sure what more I can say that isn't just repeating what's in the heritability article. "a person's offspring having 80% of their intelligence determined by their parent's genetics?" no, the heritability article explains why that's not what a heritability of 0.8 means. "Is a person's intelligence, on average, determined 50% by genes and 50% by environment, or what?" no, again, the heritability article explains that heritability measuresestimates the relative contribution of genetic to envrionmental variance to phenotypic variance. It's an approximate measure of the relative strength of genetic effects to population variance in phenotype. Pete.Hurd 17:25, 18 September 2006 (UTC)

Ok, thanks for answering anyway. But in your opinion, what would you say is the average contribution to someone's intelligence in terms of environment and genetics?

## History

The History section discusses the impact of science on society, but not the impact of engineering. While the science of behaviorism is in its infancy, and as such has not yet given rise to noticeably useful behavioral engineering, note that in other areas of conflict between science and various cultural or religious orthodoxies, the trend has been for society to be won over almost precisely when science gives rise to engineering which delivers more in the way of desirable benefits than the pre-existing orthodoxies were delivering. If this pattern holds in the future, we might predict, for example, that if a scientific theory of human behavior gives rise to a therapy which cuts recidivism among criminals to zero, at far less cost than the current criminal justice system, the benefits to society and to the former criminals themselves would probably cause people either to abandon their previous orthodox beliefs (which were not even as effective as prisons for preventing crime), or to modify their orthodox beliefs so as to accommodate the newly demonstrated scientific reality. Every religious world view is subject to revision (not to mention schism), as demonstrated by large segments of Christianity, which have famously reversed or adjusted their positions on such issues as slavery, geocentrism, and usury, and are now in a gradual struggle to liberalize their views on divorce and homosexuality. As another example, it is fashionable for Muslim radicals who claim to reject what they consider to be godless Western values to pose for photos with the AK-47 as a prop. The AK-47 easily overcomes its origin in an officially atheistic country because it is a demonstrably excellent light infantry weapon. In any case, during the early stages of a scientific discovery, when scientists are merely challenging orthodoxy without doing anything that makes people feel better than the existing orthodoxies make them feel, then of course the layman is going to have a problem with the new ideas (when they are merely troubling as opposed to useful), because the average person tends to judge the truth of ideas according to how they make him feel. Teratornis 18:50, 14 November 2006 (UTC) Pete Hurd get a life you nerd

Just a small thought on the history of the nature-nurture debate. Anybody notice that it is almost exclusively behavioral characteristics that generate this debate, but not morphological characters, such as body lenght and such? Also, the debate concerns almost exclusively Homo sapiens, not other species. Crusio 22:22, 25 March 2007 (UTC)

Aye, it's been a while since I looked in on Human height but it was depressing to see how resistant most contributors there were to GxE thinking. Cheers, Pete.Hurd 22:54, 25 March 2007 (UTC)

## npov

this article give undue weight to the influence of genetics or Nature. If it is a debate then both sides need to be heard. for example

"With the development of human genetics, many important human traits have been proven to be partially or mostly genetic. "

this is POV because it does not quantify how many important human traits and how partial or "how mostly" they are genetic.Muntuwandi 15:29, 6 June 2007 (UTC)

The reason why the article gives such weight to genetics,is because, quite frnakly, nature kicks nurture's ass in most twin and adoption studies. To state this is a scientific way: The portion of the variance for most traits (like adult IQ and the Big 5 Personality Traits) that can be attributed to heritability (i.e., the effect of genes) is substantial, while that portion attributed to the effects of family environoment (i.e., those effects shared by two siblings reared in the same home) is often negligible. I do not see anything controversial about this from a scientific point of view (hundreds of twin and adoption studies confirm this), so I removed the banner. Although the "nurture" component often turns out to be a big dud, all traits are at least partially heritable. Boab 20:56, 19 June 2007 (UTC)

Actually, Boab, some scientists do wonder why h2 estimates in human studies turn out so high. In most studies of animal behavior, h2 is much MUCH lower. And in the latter studies, one does everything porssible to "boost" h2: rear all animals in an environment that is as standardized as possible, for instance. I didn't really agree with Muntuwandi's comment, but I don't agree with yours either. If you have access to it, read "Beyond Nature and Nurture in Psychiatry" edited by Jim McCabe (Informa Healthcare Publishers). There's an interesting chapter in there suggesting that because of their very design, human behavior genetics studies are bound to underestimate the effects of shared environment and, hence, overestimate h2. Crusio 22:22, 19 June 2007 (UTC)

## Polgar "experiment"

The N vs N debate is probably based on some examples that opposing sides use as arguments. That was the point of the section that I added. I still think that 'examples' section is needed. Lakinekaki 07:23, 8 September 2007 (UTC)
ps. ...the Polgars don't know up from down when it comes to behavioural genetics... they however seem to know enough about education (a.k.a. nurture), as knowing chess and knowing how to teach chess are two different things. Lakinekaki 07:23, 8 September 2007 (UTC)
It it the very notion that the Nurture vs. Nature debate has "opposing sides", a view which has been so soundly rejected by psychology for the last fifty years or so, that makes the addition of such a point non-constructive to the article. Pete.Hurd 16:48, 8 September 2007 (UTC)
?! Whatever. I guess I don't understand what you are saying. Lakinekaki 18:41, 8 September 2007 (UTC)

## Heritability of IQ

This article is extremely biased in favor of the hereditarian position. On the heritability of IQ, it cites just ONE source, that being Bouchard- and this study giving a ridiculously high heritability- .86! Most twin studies show an average heritability of .50, and the hereditarian position typically gives a range of .70-.80, not the nearly .90 given here. Who put this garbage together? —Preceding unsigned comment added by 76.103.68.182 (talk) 20:08, 23 October 2007 (UTC)

Ummmm, you seem to be referring to the sentence that reads "monozygotic (identical) twins raised separately are highly similar in IQ (0.86)" which is clearly reporting a correlation, which is completely different number from the heritability. You seem a bit confused, and perhaps you should read up on the relationship between r and ${\displaystyle h^{2}}$. The one paper cited that you complain about is a review, from the abstract "I review representative biometric studies of adult twins and adoptees that have been used to generate estimates of genetic and environmental influence on intelligence (IQ) and special mental abilities. The various studies converge on a heritability estimate between 0.60 and 0.80 for IQ." I think the standard textbook on the topic (Plomin et al Behavioral genetics, 4th ed) represents the scientific consensus when it reports that "the average twin correlations are 0.86 for identical twins and 0.60 for fraternal twins" (p166). As for your question "Who put this garbage together?" the answer can be found here. Pete.Hurd 21:49, 23 October 2007 (UTC)

Well, I guess I did misread it, sorry- still, why is there such a lack of direct details on average heritabilities of IQ on this page? —Preceding unsigned comment added by 76.103.68.182 (talk) 03:00, 28 October 2007 (UTC)

I think the reason it's covered so briefly here is that it's covered more completely in other articles, e.g. IQ#Heritability, Inheritance of intelligence, and it is of value to have an article on heritability that deals with the concept itself. Believe it or not, despite the impression one gets reading Wikipedia, there are scientists that study heritabilities of traits totally inconnected to IQ... Best regards, Pete.Hurd 05:36, 28 October 2007 (UTC)

Same commenter here- I know alot about behavior genetics, but either way, it should be considered on how this article gives such scant details. —Preceding unsigned comment added by Danube07 (talkcontribs) 04:47, 30 October 2007 (UTC)

I'm fine with it giving nothing at all about IQ, why replicate the same paragraphs over and over...? In the interests of most efficiently leading readers looking for that material to the best treatment of it, I think a {main|[Inheritance of intelligence}} (or somesuch thing, I havn't read the articles to see which gives the best treatment) might be a sensible option. Pete.Hurd 19:11, 30 October 2007 (UTC)

## Error in First Sentence

It is impossible for nurture (upbringing) to determine PHYSICAL traits. The first sentence is absurd to the extent that it includes this reference. —Preceding unsigned comment added by JackStoneIsRight (talkcontribs) 03:41, 8 January 2008 (UTC)

Nope, that's not a mistake. Things like nutrition (or nutritional behavior) can obviously influence physical traits. And think also of excercise and muscle mass.... --Crusio (talk) 10:34, 8 January 2008 (UTC)
Prenatal maternal stress is an environmental factor, and that influences morphological traits... Pete.Hurd (talk) 17:22, 8 January 2008 (UTC)

## Weasel Word

"many modern psychologists consider the question naive - representing an outdated state of knowledge." How many? Is there a consensus? --Coching (talk) 04:06, 26 January 2009 (UTC)

## Intelligence Citations Bibliography for Articles Related to IQ Testing

You may find it helpful while reading or editing articles to look at a bibliography of Intelligence Citations, posted for the use of all Wikipedians who have occasion to edit articles on human intelligence and related issues. I happen to have circulating access to a huge academic research library at a university with an active research program in those issues (and to another library that is one of the ten largest public library systems in the United States) and have been researching these issues since 1989. You are welcome to use these citations for your own research. You can help other Wikipedians by suggesting new sources through comments on that page. -- WeijiBaikeBianji (talk) 02:57, 9 July 2010 (UTC)

## Congratulations

Good work here on discussion of heritability estimates. In many respects, this article has the best discussion of the concept of heritability among the several Wikipedia articles that mention the concept. I'll read the section carefully several times as I delve into sources on the issue that I hope to use as a basis for updating the other articles on Wikipedia that mention heritability. -- WeijiBaikeBianji (talk) 22:13, 22 September 2010 (UTC)

The congratulations for the general treatment of heritability here still leaves plenty of room for better sourcing of the section of this article pertaining to IQ scores, which needs to be updated and rewritten with current standard terminology. -- WeijiBaikeBianji (talk) 04:46, 2 October 2010 (UTC)

## The Rectangle Quote

I believe it's a bad idea to give the rectangle quote from Donald Hebb such prominence. Rather than illustrating a single cause fallacy, it actually makes a fallacy by implying you can't identify independent contributions of genes vs. environment. Indeed, you can distinguish the two with pretty good resolution using behavioral genetic method, and eventually with great resolution using genome scans.

The rectangle metaphor is flawed because, if you had a "population" of rectangles, you could indeed see whether variation in area was caused more by height or by width, using the same methods already used in behavior genetics.

I'm not against including this in the article, but I just want to note that it make a contentious, and in the view of many professionals who study the nature vs nurture question--false, view. Thus, I think we should move it down into the Scientific Approach section, where it can be discussed/critiqued.--Babank (talk) 22:21, 2 April 2011 (UTC)

made sense, so I have done this. I think it reads well there.
Nice. Will add a reference so its not original research.--Babank (talk) 19:22, 8 April 2011 (UTC)
I also removed the 3 older references for the Hebb quote. Why exactly do editors quadruple reference things like this?--Babank (talk) 19:26, 8 April 2011 (UTC)

## Controversy and Debunking

Huh? What theory is referred to in the first sentence? I can't understand this section, and the very term "debunking" is rather inflammatory.It does have a reference, apparently on primate behavior. While I can see the connection to the issue, normally people are talking about human behavior in this subject. Should this section just be deleted? Robertmacl (talk) 20:07, 31 December 2011 (UTC)

I'd support deleting it. Even assuming this is referring to something credible with regards to human behavior, the idea that one set of experiments could "debunk" the interplay between nature and nurture is absurd. Gukkor (talk) 08:02, 12 February 2012 (UTC)
I've removed the entire section as it gives undue weight to a single study without putting it into the general context of the topic or the article.·ʍaunus·snunɐw· 15:02, 12 February 2012 (UTC)