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Thread: The genetic component of IQ increases with age.

  1. #1 The genetic component of IQ increases with age. 
    Forum Radioactive Isotope skeptic's Avatar
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    From an article in New Scientist.
    http://www.newscientist.com/article/...mg20327174.600

    This follows a study comparing identical and fraternal twins, showing that the genetic as opposed to environmental influence on IQ increases with age.

    I quote from the article :
    "Plomin's team calculated that in childhood, genes account for about 41 per cent of the variation in intelligence (see graph). In adolescence, this rose to 55 per cent; by young adulthood, it was 66 per cent (Molecular Psychiatry, DOI: 10.1038/mp.2009.55)."


    Interesting ....

    Anyone care to speculate on why?


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    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
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    Maybe the decrease in functionality of a person's brain due to aging is so great that the changes environment can cause to improve IQ are not as influential. Although, I'd think diet and environment would still have an effect. Since studies have shown that certain diets and lifestyles prevent neurodegenerative disorders.

    Maybe a neurobiologist is lurking in the wings?


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    Forum Professor marcusclayman's Avatar
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    Early in life we are "designed" to learn from our environment. Later in life we are "designed" to spread our genes.

    So it makes sense that earlier in life our environment determines more about who we are than later on. After all, you don't make babies by sharing experiences.
    Dick, be Frank.

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    It depends on how they define the genetic component. I can see an error if they refer to the neuron pathways that are long established.
    Since in learning, some pathways are not used and they degenerate, we can say that this genetic pathway has been lost. So at some age, around maybe 5-7? alot of genetic material has been lost. Alot of learned pathways are added up until an adult has learned most of their stuff at about 26?. What do we call the result and how can we measure it? The paper should give you a lead? Do they propose that the pathways in place at 26 are therefore genetic? In that case, it's no suprise that we learn very little new form then on.

    ex: 2 experiences in my 20's gave me a realization that I had not heard any totally new sounds for a very long time. One was a man who jumped in front of a subway. I had never heard that sound before. It was like a wet billiard ball - but I realized I had no other reference aside from the association. The other was a meteroid that hit on the other side of a river. I thought some men were putting away a huge scaffold and it had dropped onto the street it was so loud. It was metallic - but it was also a thud and not a bouncing noise like heavy metal makes when it falls.

    These would measure as new, 'non-genetic' phenomena against the much older and established pathways? Is that what the authors would hold?
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    Forum Radioactive Isotope skeptic's Avatar
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    Sensei

    Genetic component is an outcome of the experimental method. Essentially it is calculated from the degree of difference in IQ between the two identical twins versus the degree of difference between fraternal twins. This is because identical twins are genetically identical, while fraternal twins share only 50% on average of the same parental genes.

    Fraternal twins should, to the same degree as identical, share the same uterine environment and the same post natal environment. Thus, if their IQs diverge more than the IQs of identical twins, the greater divergence is due to different genes.

    From this is calculated the genetic component of IQ.
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    The only confounding variable question I would have to that setup is the age/number of identical twins the study uses. The older they are, the more likely for different gene portions to jump the gap and swap with their counterpart. The earlier in a baby's life it does occur; the greater the drift difference; it matters not a whit until you are looking at ID twins as a pair.
    I can't remember the name for this mechanism, nor do I recall how commonly it occurs. But it does make Identical twins more and more different as they age, and therefore to an unknown degree, fuckup your assumption that ID twins are fully ID for their genetic components.

    Of course, there is no way to counter this within cells. So, we pretty much ignore it in Psyc studies. I know of no study that tries to document to what extent this can screw measurements up.

    Just thought I'd let you know about it though.
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