Q22 - Researcher: The role of chemicals

[savvysinger]

Hello there,

I chose answer E, partially because I couldn't figure out how best to narrow down the answers. The only answer I confidently narrowed down was C, that free will can be found only in humans. What's the best way of going about this?

Thanks!

[ManhattanPrepLSAT1]

This one is very typical of a necessary assumption. If you get good at spotting the difference between a sufficient assumption and a necessary one, your life will become much easier.

To find a necessary assumption we can apply the negation test. If the negation of the answer choice would destroy the conclusion, then it was needed in the first place, and is the correct answer. However, if the negation of an answer choice would not destroy the conclusion, we should dismiss it.

Premise
Humans choose how they behave. (ie: they have voluntary action)

Intermediate Conclusion
Human action has a psychological explanation.

Main Conclusion
So pheromones are merely a vestige of our evolutionary past.

There are two gaps

1. Premise ---> Intermediate Conclusion
2. Intermediate Conclusion ---> Main Conclusion

The correct answer could choose to focus on either gap, but in this case the correct answer focuses on the first gap.

(A) is too strong. While this is sufficient to bridge the gap between the premise and the intermediate conclusion, it is not required to establish that psychological factors were at play.
(B) is necessary to the argument. If voluntary actions could have chemical explanations, then the argument couldn't say that psychological factors were at play. Potentially, the behavior could then be explained chemically.
(C) is way too strong.
(D) is irrelevant. The choice is between a chemical explanation and a psychological one. The author never ruled out evolution as playing a role.
(E) mixes up the terms. It's not a psychological explanation of pheromones but rather of sexual behavior.


Tough question, but I hope this helped clear things up!

[tamwaiman]

I don't think that (B) makes a strict assumption because it is acceptable that psychological factors have an explanation with other chemicals except pheromones.

Will it better if (B) says "voluntary action cannot have a pheromone explanation" ?

Thank you.

[ManhattanPrepLSAT1]

I don't think that (B) makes a strict assumption because it is acceptable that psychological factors have an explanation with other chemicals except pheromones.

Ah! I think you've got it turned around. It's not about whether psychological factors have an explanation, it's about the explanation of voluntary action.

There's an intermediate conclusion here. Answer choice (B) is needed to arrive at the intermediate conclusion that psychological factors take over. The evidence for this is that humans have voluntary action.

So the argument reads...

Humans have voluntary action. Thus, psychological factors have taken over.

The argument assumes that voluntary actions cannot have a an explanation other than psychological factors (ie a chemical explanation) - this is best expressed in answer choice (B).

Does that make sense? If you see it differently, I'd love to see.

[Yu440]

Hello,

I would like further elaboration on how to eliminate answer choice E.

My understanding is that for the argument to be valid, a psychological explanation for the continuing presence of pheromones in humans isn't required. What is required is that we don't have a chemical explanation for the presence of pheromones. Is this correct? Thanks!

[ohthatpatrick]

We actually don't need a chemical or a psychological explanation for the continuing presence of pheromones in humans.

The author is offering an evolutionary explanation for pheromones, saying that these chemicals are present in organisms in order to guide the organism's sexual behavior (presumably towards mating and replicating the genes).

He is calling pheromones a vestige of our evolutionary past, which is a way of saying "this doesn't have any usefulness to us anymore, but it's still in our genes".

I don't know if you've ever heard of humans being born with "vestigial" tails. You've probably heard of our "tailbone". And when we're a developing embryo, for a time in the womb we actually have a tail!

There's no chemical or psychological explanation for the continuing presence of tails in human embryos (or in rare cases, in human children). It's just an artifact of genetics. We evolved from creatures who had tails and needed them to survive in their environment. Our genes still carry the programming to make a tail, even though the human species ended up thriving in its environment without need for a tail.

That's how this author is referring to pheromones. He understands the evolutionary explanation for why these chemicals exist in our body, but he thinks the role they play for other animals is not a role we need them to play. Thus, they're just useless genetic baggage that comes with our DNA recipe, even though we (supposedly) don't use them to determine our sexual behavior.