Identical Twin Studies vs. Nurture over Nature

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Here's something I've heard from people, seems like its something that people vary on a bit but it also seems pivotal in how people analyze the world as well as how they may inflate/deflate other people around them as well as past present and future. It makes the difference also in whole political ideologies as well.

Which is that? The nature/nurture argument. Its one of those where it seems like it would be minor on the face of it but when you think about it it has sweeping implications on a person's outlook on politics, religion, philosophy, humanity in general, almost by definition.

So, that said, I remember seeing a show on identical twins...geez...I think this was probably back in the early or mid 90's. The idea was this - the twins in this study in all cases were raised apart from each other, did not know each other, were grown adults when they did meet, and they were trying to figure out how much difference in their behavior or personalities that there would be based on the differences in style of upbringing. What the show seemed to reflect was that it didn't matter if the identical twins grew up in the same house with the same parents or grew up in a house thousands of miles away; they turned out almost as identical in traits, careers, interests, etc. either way.

The question I have on this, for those of you who have an interest in doing the research past the anecdotal - what do you think this means in the broader sense regarding the nature/nurture argument? To me this is very important just because, its a big deal. That and if there is a known reality on this one, hiding out from it for political reasons seems just as disingenuous and negative in its end math as hiding out from it for religious ones.

Well, I'm done jabbering on - feel free to take a stab at this.

Nature is greatly important. Many studies on personality find that genetics accounts for about 50% of variation in many personality characteristics. This is greatly important given that the sum of other sources(such as parenting, background, etc) would have to be relatively small compared to personality characteristics.

Nature-Nurture Gene Link Sheds New Light On Autism
http://www.sciencedaily.com/releases/20 ... 211651.htm

Nature on genes and autism: nurture may not be so different!
http://blogs.psychologytoday.com/blog/t ... -different

Last edited by asplanet on 12 May 2009, 11:39 pm, edited 1 time in total.

enviroment plays alot, genetics play another part. mix all these together and you get a perfect person. mess with one or the other and you get problems

I have also heard of this instance of similar separated twins. This subject confuses me and makes me wonder if it might be a fluke. I have known a few sets of twins who shared nurture and they are so different from each other.

Last edited by claire-333 on 12 May 2009, 11:50 pm, edited 1 time in total.

What is a perfect person did not know one existed we are all born different!

Me and my twin brother are total opposites and brought up the same, mind you he is male!

a little jesus christ mixed with some leatherface is what i mean. people can be twins and not related without having the same sensations, experiances and growing up the same. what im saying is it depends

I agree - it might be somewhat higher, might be somewhat lower, but genetics are quite important. The idea that we can be 'whatever we want' is partly a myth. We can do incredible things if we are motivated, but there are limits based on biology.

One of the twins studies as presented on TV was kind of misleading ... they focused on superficial similarities that probably had little or no significance - for instance, in one pair of twins, both brothers married a woman named Mary (which was one of the most common names back then)... it was like numerology, where a large quantity of data was sifted to come up with 'amazing coincidences' ... any two data sets have a large number of coincidences, nothing amazing about that.

No doubt, if you separate identical twins at birth and raise them apart, the twins will be far more alike than any two random people. But much of this will be related to their overall temperament or personality.

Well, I am getting my numbers from a paper called "The Case for a Nietzschean Moral Psychology" by professors Brian Leiter and Joshua Knobe

Which has the following quotes:






Paper found here: http://papers.ssrn.com/sol3/papers.cfm? ... _id=816224

Hmmm, The Case for Nietzschean Moral Psychology seems odd, at least from anecdotal experience and observation (unprofessional of course and unreliable but debatable), child upbringing seems to have more impact than the article suggests, I mean, things like compassion, sympathy and empathy, as well as appropriate behaviour and criminal behaviour, yeah I get that part of these are genetic traits but also learned. If a child is trained to be a soldier to fight on a war since very young, or trained into terrorism since a very young age, I could argue that the impact seems to be significant in that case, not to mention traumatic experiences and things like domestic violence, child abuse vs the considered appropriate raising during childhood.

I get that moral behaviour would differ from moral ideology though, which that can be said to be learned due to external environment and stimuli, as the brain is somehow "empty" at birth and is getting new information from the simuli, I mean, the way we think, our perspective and opinions about many things are based on our own personal experience, in which if the experience would have been different we would have different views. So the issue to take into accout would be "learning", so I actually doubt that that child upbringing and the experience with the environment and stimuli to be of little significance, it seems to be more than that, but then, I may be refering to moral ideology more than moral behaviour.

Problem I see often with psychology is the social and cultural aspects of different cultures, given that I believe that socioeconomical, political and cultural aspects to be influential in some part, which could be problematic with some of my argument as well.

But that's my humble opinion.

Yes, those are consistent with other things I have read, and quite plausible. I would put the genetic factor for 'personality' around 40% to 60%, which variances for people that have unusual circumstances ... for example, a child raised in a box with random shocks will have a very different personality than most people, and it will be due much more to environment than genetics. But for the average person, about half is reasonable for a rule of thumb.

Well, that's a good point.