Journalist: Scientists took blood samples from two large, diverse groups of volunteers. All the volunteers in one gro...

shunhe on May 13, 2020

Hi @BrookeMag,

Thanks for the question! So let’s take a look at the argument first. We’re told that scientists take blood samples from two groups of volunteers. Group one is made up of people who like vegetables, whereas group two is made up of people who don’t like vegetables. The blood samples of group two all have a gene in common. The argument then concludes that a dislike of vegetables may be genetically determined.

Now we’re asked to find a weakness in the argument, and this is when we might begin to anticipate some possible weaknesses. One possible weakness that comes to mind is that we know that group two has this gene in common, but we don’t know whether group one has it or not. Why is this important? Well, this gene might be one that all humans have in common, and if it is, then it doesn’t mean anything special that all the people in group two share it. For example, let’s say that the scientists did another test and they found out that all the people in group two have something in common: their cells have mitochondria in them. Can the scientists then conclude that disliking vegetables is linked to mitochondria? No, because the people in group 1 would have that too; it’s not something that’s linked specially to the people in group two. This is what (E) tells us—the argument assumes that having this gene is a special trait of group two, when we don’t know that that’s the case.

Hope this helps! Feel free to ask any other questions that you might have.

mikeheath on January 8, 2021

Hi,

I missed this question because I mistakenly thought it was the negation of what it is.

Can you help me make sure I have it right?

“E: It takes for granted that the volunteers in the group that enjoyed eating vegetables did not also all have the XRV2G gene in common.“

I interpret this choice as saying “the volunteers in the group that enjoyed eating vegetables did not have the gene XRV2G”, which I would rule out because that seems to strengthen the argument. Can someone help me understand this?

Greta on August 9, 2022

@Michael Hey I'm not an instructor but your interpretation is just slightly off. E is saying that the argument is not doing its due diligence and fails to inform us whether the vegetable enjoyers also have the XRV2G. Therefore, it is possible that all the participants do in fact have the gene, which would make the argument invalid. Without being informed of this explicitly, there's no way to know for sure, meaning that the argument is taking this fact for granted. Hope this helps!