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.
Just give your child a mobile device. You won't have to worry about making eye contact again, until you take it away :^) Really, not worrying whether your kids learn to pay attention to eyes and faces to understand other people around them, is about like not worrying whether they learn to speak or read. These things might just happen, but if they don't you will both be really miserable by the time they are 10.
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.
> 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.
It really helps communication for many people. People with limited hearing rely on some level of lip reading, in addition to just following body language.
Also, if you are maintaining eye contact, you are generally pointing your face at the other person, and that REALLY helps your voice get to their ears.
I have a friend who talks to the ground and I have to consistently ask her to repeat herself.
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!
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.
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.
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%.
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.
"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.
Yes, and in order to state "this is definitely a genetic cause" you would need to rule out other factors. Including fraternal twins is interesting, but unless they were separated at birth (and not even then really) this could just as easily read "How Kids See the World Depends a Lot on How They Were Raised" which is a pretty obvious conclusion to draw and not particularly headline worthy.
That's exactly what is getting ruled out by using fraternal twins and identical twins - you measure the difference of this effect between these groups.
If the outcome was determined by how they were raised (or where they lived, or who their parents were), the link would be equally strong between fraternal twins and identical twins; but if the outcome depends a lot on genetics, then the effect will be much stronger in identical twins than in fraternal twins. This does rule out pretty much all other factors except genetics.
Thank you for clearly sharing how and why scientists can accurately measure genetic effects in twin studies. You are correct in your assertion that mono vs di - zygotic twin studies are usually good measures of heritability.
I would add a slight technical caveat. Twin studies are excellent at measuring additive genetic effects, i.e. when different genes add together nicely to contribute to a trait (height is a good example). Twin studies typically assume that genes do not interact in funny ways (e.g. epistasis). Thankfully, for many, but not all, traits examined the additive genetic effect catches most of the heritability.
If epistatic interactions drive a trait, however, the statistical models typically used in twin studies would actually under-estimate the influence of genetics.
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?
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[ 0.20 ms ] story [ 15.3 ms ] threadIt 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.
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.
It really helps communication for many people. People with limited hearing rely on some level of lip reading, in addition to just following body language.
Also, if you are maintaining eye contact, you are generally pointing your face at the other person, and that REALLY helps your voice get to their ears.
I have a friend who talks to the ground and I have to consistently ask her to repeat herself.
Some context: http://www.robertsapolskyrocks.com/behavioral-genetics.html
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.
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.
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.
If the outcome was determined by how they were raised (or where they lived, or who their parents were), the link would be equally strong between fraternal twins and identical twins; but if the outcome depends a lot on genetics, then the effect will be much stronger in identical twins than in fraternal twins. This does rule out pretty much all other factors except genetics.
I would add a slight technical caveat. Twin studies are excellent at measuring additive genetic effects, i.e. when different genes add together nicely to contribute to a trait (height is a good example). Twin studies typically assume that genes do not interact in funny ways (e.g. epistasis). Thankfully, for many, but not all, traits examined the additive genetic effect catches most of the heritability.
If epistatic interactions drive a trait, however, the statistical models typically used in twin studies would actually under-estimate the influence of genetics.
Further reading: http://www.apa.org/monitor/apr04/second.aspx
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.