
How Kids See the World Depends a Lot on Genetics - sciadvance
https://directorsblog.nih.gov/2017/07/25/how-kids-see-the-world-depends-a-lot-on-genetics/
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mitchellshow
Cool study, but it is my understanding that twin studies have a tendency to
erroneously assume genetic causation since they fail to control for conditions
the twins share in prenatal environments, which can (and do) affect behavior.

Some context: [http://www.robertsapolskyrocks.com/behavioral-
genetics.html](http://www.robertsapolskyrocks.com/behavioral-genetics.html)

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1maginary
They controlled for that by having about as many fraternal twins in this
study, though.

It's particularly surprising to me that they got very similar results with
regards to discrepancy between fraternal and identical twins when testing
again at a later age.

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jasonkostempski
I don't get how that could be a control against assuming genetic causation.
Fraternal twins still have similar genetics, right?

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klodolph
Fraternal twins and identical twins both have the same environment growing up,
they experience the same hormones at the same time during gestation, they live
in the same city, sleep in the same bed. They eat the same foods at the same
times of day and in the same amounts, excepting personal preference. However,
fraternal twins share 50% of their genes (on average) and identical twins
share near 100%.

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PeterisP
could it be be that such studies underestimate these effects because of this
obvious assumption that fraternal twins share 50% of their genes - IMHO they
share _more_ than that because for all genes that "matter" their _parents_
genes would be quite correlated.

Contrary to the popular saying, like attracts like. Parents are exceedingly
likely to share visible traits and also mental traits - so the correlation
between siblings wouldn't be halfway between random member of population and
an identical twin, but much closer to the identical twin.

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klodolph
"Like attracts like" is an interesting assumption, there is some evidence that
people are attracted to others that have genetic differences rather than
similarities. A common misconception, for example, is that the genetic
differences between ethnic groups are larger than genetic differences within
an ethnic group, in fact, the reverse is true, if we speak of averages. (Think
of two overlapping bell curves with means that are very close to each other,
if you want to visualize what I'm trying to say.) Or in more concrete terms,
if you select a random person with European ancestors and a random person with
African ancestors, the expected genetic similarity is quite close to the
expected genetic similarity of two random persons with the same ancestry.

Furthermore it's not actually that critical whether fraternal twins share 50%
or 75% or 90%, the important part is that identical twins share nearly 100%,
and the number for fraternal twins is significantly less, so if you see
differences for fraternal twins that you don't see for identical twins, you
can make a strong case that genetic differences explain the observation.

And finally, the idea that fraternal twins share ~50% of their genes is a bit
of a simplification. On average, two randomly selected humans will have
genetic similarity of 99.5% or so. So that "50%" quote is just a ballpark
figure scaled to the relative genetic diversity of the human population to
begin with.

Or it depends on how you measure "genetic similarity" anyway.

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KittiHawk
This makes me wonder how much differences in eye contact between cultures (in
terms of etiquette) is due to prevailing genetic influences.

Like if most of the people in a group are wired to make less eye contact,
maybe that's how the social norms get developed.

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taeric
Really neat article. I'd probably change the title to "How Kids Scan..." I was
expecting something more about the inner model folks build for what makes up
the world.

It would be interesting to me if this was somehow a physical characteristic of
the eye. I'd also be interested to know if there are somehow more "optimal"
methods of scanning than others.

Tangentially, I do worry about the emphasis on eye contact in children. It is
almost like we punish kids for not wanting to look at us. It certainly seems
to help know they are listening, but it is worrying to have tension just
because someone doesn't want to make eye contact.

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Pulcinella
High School teacher here. I generally try not to take offense when I am
talking to a student and they don't make much eye contact. Some of my
coworkers take great offense when students don't make eye contact but I think
it's just something that teenagers don't do (with adults/uthoroty figures).
Also, some of my students are giving you the most attention when they are NOT
looking at you.

Doesn't help that student desks are too damn short so talking to a sitting
student forces you to loom over them like some cartoonesque evil authority
figure. No one likes making eye contact in that kind of situation.

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kurthr
It's almost like feature detection, image segmentation, object detection,
scene labeling, and tracking are pre-wired at some level... that would make
learning a lot faster!

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clarkevans
Earlier eye tracking results by the Marcus Autism Center's Ami Klin and Warren
Jones is described a 2011 TED talk:
[https://www.ted.com/talks/ami_klin_a_new_way_to_diagnose_aut...](https://www.ted.com/talks/ami_klin_a_new_way_to_diagnose_autism)

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ddebernardy
It's not clear from the summary or a very quick glance at the articles whether
the researchers controlled for sex differences or impact on parent attitudes
towards fraternal twins. It is sensible to assume that one sex will imitate
dad while the other will imitate mom, or that one toddler receives more
attention than another from either parent. Might anyone familiar with the
topic have some insights on this?

