Logical reasoning PrepTest 117 · Section 2 · Question 4

Incorrect. If anything, this eliminates an alternative cause, providing strength to the conclusion that it was humans who killed the birds.

Incorrect. We need more information to analyze this answer. Did these uninhabited islands become inhabited around the time the birds started dying off? Without knowing that, we don't know if this provides more examples of the cause and effect coinciding, or counterexamples.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
Around when humans arrived on Tiliga Island, the bird population became smaller and much less diverse. Humans caused this drop.

Answer Anticipation:
The most common flaw in Weaken questions is a correlation/causation flaw, so we should always be on the lookout for causal conclusions and correlative premises when dealing with this question type.

A timeline discussion often presents a correlation, and that's true here. The premises establish that the decrease in the bird population and diversity coincided with the arrival of humans, who ate the birds. From this, the argument concludes that humans decreased" the bird population/diversity—and "decreased" describes a causal relationship. This argument, therefore, does feature a correlation/causation flaw.

When a Weaken question has a correlation/causation flaw, there are some common answers we can look for:
(1) ID an alternative cause (what else could have coincided with the arrival of humans that killed off the birds?)
(2) Counterexamples (bird populations and diversity decreasing without humans; humans arriving and not hurting bird populations)
(3) Reversed causality (this doesn't make sense here—first, the timeline doesn't match up; second, why would a decrease in bird population cause humans to arrive on an island?)

Answer Explanation:
This answer provides an alternative cause—microbes that arrived around the same time as humans killed off the birds, not humans. In providing an alternative, this answer weakens the causal relationship in the conclusion.

Key Takeaway:
When confronted with a Weaken question (or a Strengthen question), look for correlative and causal language, as correlation/causation flaws are the most common error in reasoning in these question types. When that flaw is present, there are answer "categories" that you can look for to make the work a lot easier.

Incorrect. It's not surprising that these birds were still dying before humans showed up—it's not the island of immortal birds. There's no claim that humans were the sole cause of bird death—just the cause of the decrease in the overall population and diversity.

Incorrect. What's flying got to do, got to do with it? Without tying this into humans hunting them, this answer is out of scope. And if we squint" to get it in scope, then this would strengthen the argument, as it has to be easy to hunt birds that can't fly.