Showing Revision 2 created 05/24/2016 by Udacity Robot.

1. Title:
   Nature nurture and IQ - Intro to Psychology
2. Description:

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   Now, let's look at how nature and nurture affect IQ. Identical twins share 100%
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   of their genetic make up. They're genetically identical. Fraternal twins share
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   only 50% of their genetic makeup. This is also true for siblings and parents.
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   So, you share 50% of your genetic makeup with each one of your parents. So 50%
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   with your mom and 50% with your dad. And you share 25% of your genetic makeup
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   with your grandparents. Aunt, uncles, nieces and nephews. And people you are
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   not related to? Well, you guessed it, you share 0% of your genetic make up with
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    that. So we can turn these percentages into numbers ranging from 0 not related
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    to 1 being identical twins, this is called genetic relatedness. Now,
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    environment has to vary too. Typically, biological parents and children live in
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    the same household. But that doesn't necessarily mean they have the exact same
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    environment, but it is very similar. Now of course, there's also cases where
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    biological parents and siblings are raised completely separate from each other.
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    For example, when people are adopted. Now, let's look at a graph to show how IQ
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    is related to different types of nature and nurture. Here are our IQ
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    correlations. Remember, 0, 1, 2, 3, not very good. They're not really related.
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    But high correlations mean they're really similar. And here, we'll see if they
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    share an environment or not. Meaning if they live together or if they don't. So
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    first, lets look at identical twins. They have a one on genetic relatedness.
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    Here we can see that identical twins who were raised together have a 0.85
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    correlation between IQ scores. So because they're genetically identical, and
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    they were raised in the same environment, their IQ scores are really similar.
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    But we know nature matters because identical twins who also have a one in
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    genetic relatedness because they're genetically identical, but were raised
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    apart. So they didn't share the same environment, have a 0.75 IQ correlation.
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    Meaning they're still really similar, but not as close as if they were to live
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    together. Now, let's look at genetic relatedness of 0.5. Meaning sharing 50% of
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    your genetic makeup. So fraternal twins share 50% of their genetic makeup.
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    Those who were raised together, so they shared an environment have a
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    correlation of about 0.6. So that's pretty related. However, if they're raised
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    apart, it goes just below .4. Showing that environment does play a big factor
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    in IQ. Siblings again, who you share 50% of your makeup with. Those who are
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    raised together with a shared environment have just below a .5 correlation. So,
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    it's not very related. However, if the siblings were raised apart, so they
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    didn't share an environment. This significantly drops to just above a 0.2,
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    which is a really low correlation. And parents who raise their children, so
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    sharing an environment with them again have less than a 0.5 correlation.
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    However when they didn't share an environment, again it drops to about a 0.2.
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    These show the importance of environment. Now, lets look at adoption. So these
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    people have 0 genetic relatedness but they share the same environment. So
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    adopted siblings are just above a .3 in their IQ correlation and adopted
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    parents are just below a .2 in their correlation. Even thought they shared the
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    same environment, they didn't have a very strong correlation among IQ scores.
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    That shows us that genetics are an important factor too. The formal conclusion
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    of these studies says about 50% of the differences between people's
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    intelligence is due to genetic influence. In about 40%, its due to
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    environmental effects. That leaves 10% being unexplained. So we just don't know
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    yet.