#6 - If newly hatched tobacco hornworms in nature first feed

[Administrator]

Question #6: Strengthen, CE. The correct answer choice is (B)

Here we have another Strengthen question, making this the fourth Second Family type to appear in the first six questions (along with 2, 3, and 5). This particular stimulus presents an interesting duality: if newly-hatched tobacco hornworms eat nightshade plants first that’s the only type of plant they’ll ever eat, whereas hornworms that feed on other plant types first will continue to eat plants other than nightshades (and possibly nightshades as well; we’re not told).

Scientists have hypothesized that the nightshade exclusivity is due to the chemical indioside D in nightshades, which habituates young worms’ taste receptors and without which subsequent, non-nightshade plants do not taste good.
Essentially it’s an argument of conditioning: first exposure creates a singular, unshakeable preference.

Clearly this conclusion is highly causal—the taste of the chemical in the first meal causes an exclusive attachment to it for life—so we need to think about how to strengthen a causal argument. In this case, the two most likely ways seem to be eliminating an alternate cause (denying something else other than taste that causes hornworms to prefer only nightshades after a first exposure), or showing that the cause (preference for the taste of the chemical) and effect (insistence on a nightshades-only diet) are intrinsically connected by their co-existence and/or co-absence.

Answer choice (A): does not add any meaningful information to support the scientists’ hypothesis, but merely echoes the premise in the first sentence that they feed on nightshades only. A preference for one variety over another doesn’t matter within the family itself.

Answer choice (B): This is the correct answer choice. As expected, here we have a fantastic example of how you can strengthen a causal argument: show that with the cause removed, the effect no longer occurs. More specifically, when tobacco hornworms that first fed on nightshade leaves have their taste receptors removed, they no longer feed exclusively on nightshade. No taste, no preference. No cause, no effect.

Does this prove that their behavior is caused by taste preference? No. But it does a very good job of supporting that position.

Answer choice (C): This answer choice might support the fact that nightshades are a common food source (perhaps even the most common), but it does nothing to help the argument that early taste experiences influence life-long feeding behavior.

Answer choice (D): is wholly irrelevant to the argument, since the hypothesis is only concerned with that particular chemical (and more generally the causal role taste plays in subsequent food source choices). The presence of other unique chemicals has no effect whatsoever on the argument in question.

Answer choice (E): only supports the broad notion that these worms’ taste receptors can in fact react to, or possibly recognize, a number of naturally occurring chemicals. This still does nothing to strengthen the relationship in the hypothesis between the taste of indioside D in nightshades and the worms’ apparent rejection of food sources without that chemical for the rest of their lives.

[TheKingLives]

Could you discuss further why A is incorrect? The stimulus says that nothing without indioside D tastes good, and if the hornworms show no preference for any one variety of nightshade over any other, it's likely because the only thing the hornworms are looking for (and care about) is the indioside D. This seems to strengthen the hypothesis.

[Paul Marsh]

Hi TheKingLIves!

it's likely because the only thing the hornworms are looking for (and care about) is the indioside D

Is that necessarily likely? Only if you assume that the scientists' hypothesis (about only indioside D tasting good to the worms) is correct. If you don't assume the scientists' hypothesis is correct, then (A) gives practically no support to the hypothesis at all.

The scientists' hypothesis uses Cause and Effect reasoning. In the eyes of the LSAT, the use of Cause and Effect reasoning in always suspect. So whenever you see a Strengthen question where the stimulus relies upon Cause and Effect reasoning, you are almost always going to be looking for an answer choice that Strengthens the causal relationship. How do we strengthen causal relationships? They are reviewed extensively in the LSAT Course Books/PowerScore Bibles, but just to sum up, there are 5 ways:

1) Rule out an alternate cause
2) Show that when the cause does not occur, the effect does not
3) Show that when the effect occurred, the cause occurred
4) Rule out the possibility that the causal relationship is reversed
5) Rule out a statistical attack on the data

If an answer choice is not doing one of these in a Strengthen question where the stimulus relies upon causal reasoning, think very carefully before selecting it - it is likely the wrong answer.

Here, the causal relationship is between the cause of taste receptors getting used to indioside D, and the effect of everything without indioside D tasting bad so worms hate it. A solid answer choice here will do employ of the 5 methods above with that relationship. Answer Choice (A) does not do any of those things; it does not address the causal relationship at all. Answer Choice (B), on the other hand, employs method 2 - when the cause does not occur, the effect does not. It is our right answer.

Hope that helps!

[KendrickFrontiers]

Hey PowerScore team,

Actually a bit confused on this stimulus. I understand why the answer is right, but I rather saw this as a conditional problem than a causal problem.

Conditional in being (if the hornworm feeds on a nightshade plant, then it only feeds on nightshade plants). I seem to stumble a lot when it comes to mixing up conditional and causal, especially when stimuli feature a lot of common conditional indicators. Perhaps I may be relying too much on indicators, but unsure. Would someone be able to explain why this is actually causal and not conditional?

Thanks!

[Rachael Wilkenfeld]

Hi KendrickFrontiers,

The critical aspect to recognize here is that it is about a possible explanation. A hypothesis or explanation is another way of saying cause. The question explicitly asks us to focus on the cause here, and that's why we treat it as a causal question. I agree there are also conditional indicators involved, but the question doesn't ask us to do anything with those. Instead, it asks us for help supporting the causal relationship that it's the habituation of taste receptors that causes the behavior of the hornworms.

Some questions will have conditional reasoning along with causal reasoning. It's critical to focus in on the question to develop a prephrase targeted to the question asked. They easily could have gone in a different direction with this stimulus.

Hope that helps!