Logical Reasoning

PT143 · S3 · Q6 If newly hatched tobacco hornworms

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If newly hatched tobacco hornworms in nature first feed on plants from the nightshade family, they will not eat leaves from any other plants thereafter.

Conclusion (causal hypothesis)

When a hornworm's first meal is nightshade, its taste receptors become habituated to a chemical unique to nightshade, making other foods unappealing.

Evidence

If a hornworm starts with nightshade, it won't eat anything else forever. But if it starts with a different plant, it will eat other sorts of plants.

Evaluate

The second we see "hypothesis" in the question stem, we know this argument will have the Explain Curious Fact structure.

CURIOUS FACT - why do hornworms get hooked on nightshade if it's their first meal? EXPLANATION - nightshade has a unique chemical, indioside D, which changes the taste receptors of the hornworm, making other food taste nasty.

We can strengthen this type of argument by 1) ruling out an alternate explanation for the curious fact or 2) helping the plausibility of the author's explanation

While alternate explanation answers are more common on Weaken / Flaw / NA / Evaluate, plausibility answers are more common on Strengthen. In particular, they love to strengthen with a "no cause, no effect" scenario. Like, .

Goal

Find an answer that reinforces the plausibility of the author's explanation (or maybe that rules out an alternate reason for getting hooked on nightshade).

6.

Which one of the following, if true, adds the most support for the hypothesis?

  1. Tobacco hornworms that first fed

    Irrelevant Distinction

    This choice discusses different varieties of nightshade and their preference, which is irrelevant. The argument is focused on the habituation to a specific chemical in nightshade, not on types of nightshade.

    4% picked this

  2. Correct

    If taste receptors are removed

    Why this is right

    This choice presents a "no cause, no effect" scenario: if hornworms lack taste receptors for the nightshade chemical, they will eat other plants. The author's causal story was 1. eat nightshade 2. insidio D changes taste receptors 3. won't eat any other plants This supports that story by showing that if you don't have #2, you don't get #3.

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

    92% picked this

  3. Tobacco hornworm eggs are most

    No Impact

    The location where hornworm eggs are laid doesn't address why hornworms develop a taste preference once they start with nightshade, making it irrelevant to the central causal claim.

    1% picked this

  4. Indioside D is not the

    Weakens (if anything)

    This choice introduces other chemicals in nightshade, which means it's opening up the possibility for alternate explanations for the taste receptor habituation. "Ooh, maybe it's not insidio D. Maybe it's some other chemical that gets hornworms hooked on nightshade."

    0% picked this

  5. The taste receptors of the

    No Impact

    This is a very weak claim, one we would probably assume is true of taste buds in any creature (that it can react to several natural chemicals). And it doesn't speak to any part of the author's causal chain for how hornwoods get habituated to nightshade's unique chemical.

    2% picked this

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