Logical Reasoning

PT102 · S2 · Q10 Insects can see ultraviolet light

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Insects can see ultraviolet light and are known to identify important food sources and mating sites by sensing the characteristic patterns of ultraviolet light that these things reflect.

Conclusion (Thus)

Insects are probably attracted to Glosomus spiderwebs because of the patterns of UV light that the webs reflect.

Evidence

Insects can see UV light and can identify potential food sources or mating sites based on the telltale patterns of UV light that those things reflect.

Glosomus webs reflect telltale patterns of UV light.

Evaluate

The author's conclusion is positing a causal hypothesis: Phenomenon X is probably happening because of Y.

So we can use our Explain Curious Fact mindset.

Curious Fact These insects are attracted to G webs. (Why?)

Explanation The G webs give off specific patterns of UV light, which insects can perceive and which is attracting them to the webs.

Now we consider the two pressure points of an Explain Curious Fact argument. 1. Alternate Explanations for the curious fact 2. the Plausibility of the Author's Explanation

Goal

Unlike other question types, Strengthen correct answers more often come from category 2 than category 1.

So we'd primarily look for an answer that adds plausibility to the Author's Explanation. We want to be further convinced that the reason insects are attracted to G webs is that they are attracted to the specific patterns of UV light reflected by the webs.

The classic formula of Strengthening a causal connection is "No Cause, No Effect". Since the author thinks that the UV reflected patterns cause the insects to be attracted to the webs, a "No Cause, No Effect" answer would sound like this: when we blocked the UV light so that it didn't reflect anymore, the insects stopped being attracted to the webs.

But, the correct answer could otherwise strengthen by ruling out an Alternate Explanation for why the insects are attracted to those webs.

10.

Which one of the following, if true, most strongly supports the argument?

When webs of many different
No Impact
We're trying to test whether UV reflected patterns cause insects to be attracted to these G webs. This answer has an experiment in which lots of different webs (are any of them G webs?) are hit with a UV light. Let's stop there. Could that experiment help us judge whether UV reflected patterns cause insects to be attracted to G webs? Sure, maybe. If the experiment showed that insects were attracted to lots of different plants that reflected UV patterns, then that would add plausibility to the idea that the insects are attracted to G webs because of their UV patterns. However, this answer simply tells us that some of the plants in the experiment didn't reflect UV. That alone tells us nothing. Were the insects still attracted to those plants that weren't reflecting UV? Or did they stop being interested, since there wasn't any UV reflecting off them? Only if we know the answer to that question can we judge any impact this would have on the conclusion's causal claim.
2% picked this
When the silks of spiders
No Impact
We're trying to test whether insects are attracted to these G webs because of the UV patterns reflected off the webs. This answer doesn't talk about the insects at all, so it doesn't give us any way to judge whether insects are attracted to G webs because of their UV reflections.
2% picked this
When webs of the comparatively
No Impact
We're trying to test whether insects are attracted to these G webs because of the UV patterns reflected off the webs. This answer doesn't talk about the insects at all, so it doesn't give us any way to judge whether insects are attracted to G webs because of their UV reflections. Like (B), this answer centers around whether or not webs are reflecting UV light. We don't inherently care whether webs do or don't reflect UV light. We know that G webs do reflect UV light, and our entire inquiry is about why insects are attracted to G webs. So discussion of whether other types of webs do or don't reflect UV light is only relevant to us if you also tell us whether insects' attraction to those webs seems to change based on whether the web is / isn't reflecting UV light.
2% picked this
When Drosophila fruit flies were
Weak Support
This involves a data point in which "Many" fruit flies (insects) seemed to be attracted to a G web that was reflecting UV patterns. So it adds some plausibility to the idea that insects are attracted to G webs because of their reflected UV patterns. But "many" is a very weak quantity that can mean as little as a handful. If 15 out of 100 flies flew to the UV-reflecting G web, that would qualify as "many" but not be very impressive as evidence. Additionally, this experiment involves comparing a real G web to a synthetic web with a similar pattern and also reflecting UV. This doesn't help us test whether or not insects are attracted to the UV, because both webs in this experiment reflect UV light of similar patterns.
18% picked this
Correct
When Drosophila fruit flies were
Why this is right
We're trying to test whether insects are attracted to these G webs because of the UV patterns reflected off the webs. This experiment sounds perfect: We've got some insects (fruit flies) and we've got a G web that has UV reflections and one that doesn't have UV reflections. This can help us assess whether insects are specifically attracted to the UV reflections. It turns out, they are! The majority of the insects chose the G web that had the UV reflections over the one that didn't.
Skill tested: Strengthen · how this choice captures the argument's function is the move to repeat next time.
76% picked this

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