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"Much of the critical evidence has emerged through the study of twins. Identical twins share all their DNA, while fraternal twins share only half - they are no

"Much of the critical evidence has emerged through the study of twins. Identical twins share all their DNA, while fraternal twins share only half - they are no more closely related on a genetic level than are ordinary siblings. Both kinds of twins, however, share a womb, a family and a cultural environment. Comparisons between the two types can thus tease out the extent to which inheritance is important." Except that different kids have different experiences growing up. The same family does not mean exactly the same life. It's just not true that genes are the only difference between fraternal twins.

miloshh 18y ago
Of course, but the point is, identical twins are consistently more similar than fraternal twins. Furthermore, identical twins are about as similar when growing up together, as when growing up apart.
- nsrivast 18y ago
  They also happen to share 9 months of very important "nurture" in the womb.
- xenophanes 18y ago
  This can all be better explained by interactions between culture and genes, than by just genes. But the studies tend to ignore those, because they're too hard to deal with. (If anyone knows a twin study which does adequately deal with gene/culture interactions, please post it.)
Devilboy 18y ago
Identical twins reared apart are much more similar than fraternal twins reared together. And to me at least it makes a lot of sense. If you share almost 100% of your DNA with someone else, I'd expect you to look the same on the outside - that's a given. In the same way I'd expect your brain to be highly similar and therefore it makes sense that you will behave similarly in a lot of situations even though you were reared in completely different environments. I mean you're not gonna get a different color hair just because of environmental differences, so applying this to brain development is not such a stretch.
- xenophanes 18y ago
  But why do you think the structure of one's brain affects personality? We have these things called universal computers. Differently structured CPUs run the same programs. It doesn't matter so much which CPU you have, they all have the same capabilities. Why should it be different with brains? I think brains are universal knowledge creation devices, and universal means universal, structural changes won't alter the feature set.
  - Devilboy 18y ago
    There's lots of research that shows that the structure of the brain IS very important in how it works and how we use it. For a good overview see Steven Pinker's How the Mind Works. Many of these studies include individuals that had isolated damage to one small part of the brain and how that affects them. They show that specific parts of the brain are involved in highly specialized activities and that the brain is not just a big, nebulous general purpose calculator.
  - charltones 18y ago
    The brain is not a general purpose computer running the "me" program. The brain _is_ the "me" program - the software is in the structure of the hardware. Different software yields different results. IANAN(...euroscientist) though, I just like reading Oliver Sacks et al., so take that opinion with a pinch of salt.

miloshh 18y ago

Of course, but the point is, identical twins are consistently more similar than fraternal twins. Furthermore, identical twins are about as similar when growing up together, as when growing up apart.

nsrivast 18y ago
They also happen to share 9 months of very important "nurture" in the womb.
xenophanes 18y ago
This can all be better explained by interactions between culture and genes, than by just genes. But the studies tend to ignore those, because they're too hard to deal with. (If anyone knows a twin study which does adequately deal with gene/culture interactions, please post it.)

Devilboy 18y ago

Identical twins reared apart are much more similar than fraternal twins reared together. And to me at least it makes a lot of sense. If you share almost 100% of your DNA with someone else, I'd expect you to look the same on the outside - that's a given. In the same way I'd expect your brain to be highly similar and therefore it makes sense that you will behave similarly in a lot of situations even though you were reared in completely different environments. I mean you're not gonna get a different color hair just because of environmental differences, so applying this to brain development is not such a stretch.

xenophanes 18y ago
But why do you think the structure of one's brain affects personality? We have these things called universal computers. Differently structured CPUs run the same programs. It doesn't matter so much which CPU you have, they all have the same capabilities. Why should it be different with brains? I think brains are universal knowledge creation devices, and universal means universal, structural changes won't alter the feature set.
- Devilboy 18y ago
  There's lots of research that shows that the structure of the brain IS very important in how it works and how we use it. For a good overview see Steven Pinker's How the Mind Works. Many of these studies include individuals that had isolated damage to one small part of the brain and how that affects them. They show that specific parts of the brain are involved in highly specialized activities and that the brain is not just a big, nebulous general purpose calculator.
- charltones 18y ago
  The brain is not a general purpose computer running the "me" program. The brain _is_ the "me" program - the software is in the structure of the hardware. Different software yields different results. IANAN(...euroscientist) though, I just like reading Oliver Sacks et al., so take that opinion with a pinch of salt.