Psychologist: Identical twins

Answer choices

1. A

   No Impact4% picked this

   Many people, including identical twins, undergo radical changes in their lifestyles at some point

   It might feel like "undergoing a radical change in lifestyle" is evidence that something environmental, not genetic, is going on. That's probably fair, but the author wasn't saying that all of our lifestyle traits are genetic. He's only arguing that some of our lifestyle inclinations, like ethics / fashion / job seem to be genetic. There can be genetically-induced changes in lifestyle too: puberty and menopause or an adult-onset cancer can all make pretty radical lifestyle changes happen.

   4%
2. B

   Too Weak4% picked this

   While some studies of identical twins separated at birth reveal a high percentage of similar personality traits, they

   The author's conclusion is only saying that "many inclinations" are genetically, not environmentally, determined. It doesn't hurt her argument if there are a few differences between identical twins.

   4%
3. C

   Too Weak14% picked this

   Scientists are far from being able to link any specific genes

   True, it would strengthen the argument if we knew that scientists had already linked specific genes to many inclinations. But the fact that they haven't yet and are far from doing so isn't evidence that those links don't exist. Or at least, it's very, very weak evidence that those links don't exist. One of the famous flaws is Unproven vs. Proven False, in which we make this very complain: just because scientists haven't proven there is a genetic basis to inclinations doesn't prove that there isn't a genetic basis to inclinations.

   14%
4. D

   Correct74% picked this

   Identical twins who grow up together tend to develop different beliefs, tastes, and careers in order to differentiate

   Why this is right

   This presents a Cause, No Effect weakener to the author's causal claim. The author thinks that in the identical twins raised in different environments, their common genes caused them to have similar ethics / fashion / career choice. But here are some data points (and many of them, because it's "tend to") in which we have common genes, but different ethics / fashion / career choice. This suggests that those inclinations are not genetically determined, or if they're genetically influenced they are still subject to environmental influence such as the intra-family pressure to be into different stuff than your sibling is.

   Skill tested: Weaken · how this choice captures the argument's function is the move to repeat next time.

   74%
5. E

   Strengthens4% picked this

   Twins who are not identical tend to develop different beliefs, tastes,

   This gives the author a No Cause, No Effect strengthener. He thinks that having the same genes leads to similar beliefs / tastes / careers, so examples of different genes leading to different beliefs / tastes / careers corroborates his thinking. Non-identical twins, i.e. fraternal twins, are still genetically similar (because they're siblings) but they're as similar as any pair of siblings that aren't twins.

   4%