Logical reasoning PrepTest 131 · Section 3 · Question 20

Incorrect. The number of predators isn't relevant to the argument, just the likelihood of predation. Having more predators might be associated with a higher likelihood of being eaten, but the opposite might be true if the predators also eat each other.

Incorrect. If anything, the argument assumes that peppered moth coloration by itself determines how well they blend in, and the moths can't change it (otherwise, the light ones would probably change things up!).

Incorrect. The argument speaks to averages among the moth populations with different colorations, so if there are minor variations in likelihood within each population, that doesn't hurt the argument.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Errors in Reasoning

Stimulus Summary:
Peppered moths use camouflage to avoid predators. The lightest peppered moths contrast most with their environment and are most likely to be eaten, so the darkest peppered moths must be least likely to be eaten.

Answer Anticipation:
Looking at the conclusion of this argument, it's about the darkest peppered moths; the premise in support of it is about the lightest peppered moths. Whenever an argument is dealing with characteristics and jumping from one end to another, it's important to consider whether that characteristic exists as a binary—it only exists in two forms, such as on/off—or on a spectrum—think temperature, where there's middle ground between hot and cold.

Coloration exists on a spectrum—there's a wide range between the lightest and darkest peppered moths. While the lightest might stick out the most against their background, that doesn't mean that the darkest stick out the least. If the background is, say, dark grey, then both the lightest and darkest moths might stick out, and the ones that are in the middle—shades of grey—might blend in the most. The flaw in this argument is that ignores the possibility that this middle ground exists and could be the best at camouflage.

Answer Explanation:
The argument jumps from the lightest moths to the darkest, ignoring that coloration exists on a spectrum. In ignoring the moths in the middle, the argument fails to establish that one of them doesn't have the best camouflage, as this answer choice points out.

Key Takeaway:
Some characteristics are binary, in that they only have two states—on/off; alive/dead. Some exist on a spectrum—temperature, height, strength. When dealing with characteristics, it's important to know if you're dealing with one that's binary or on a spectrum, especially when dealing with conditionals or conclusions that jump from one extreme to another. Note that this frequently comes up in questions about the economy—the argument will talk about the richest and poorest, ignoring the middle class.

Incorrect. Even if the moths have other defense mechanisms, the lightest and darkest moths would both have them, and coloration could still be the determining factor in which ones were most likely to be seen and eaten.