PrepTest 119

[lcid:3573] Prep Test 119 LSAT — Logical Reasoning — S2 Logical reasoning

Question prompt

Although instinct enables organisms Remaining source text redacted.
Why the credited answer is right

Credited answer: B

The notes below walk through why it fits the stem and how to eliminate the rest.

Argument or Facts

Facts

Valid or Flawed

NA

Question Type

Must Be True Questions

Stimulus Summary

Instincts require fewer nerve cells than noninstinctual behavior. Insects don’t have enough neurons to have a brain mechanism that can perform noninstinctual behavior.

Answer Anticipation

This stimulus pulls a neat trick - halfway through, it switches from discussing instinctual/noninstinctual behavior to discussing flexible behavior. It does note that this is the same thing as noninstinctual behavior, but let’s not play their games - when they say flexible, think noninstinctual.
Why is this important? Because “instinctual” and “noninstinctual” have a relationship that “flexible” doesn’t have with either word. The former are much more clearly a set of words that represent all types of behavior - “non-” as a prefix means “not whatever comes after.” As such, things are either instinctual, or they’re not instinctual. “Flexible” muddies that water.
So when the argument establishes insect brains as too small to support “flexible” behavior, that means the same as saying that their brains can’t support noninstinctual behavior. All that’s left, then, is instinctual behavior, and so let’s find an answer stating that this is the type of behavior insects are limited to.

Answer choices

  1. A
    The behavior of organisms Remaining source text redacted.
    Why choice A is not credited
    While organisms with elaborate brain mechanisms are capable of acting flexibly/noninstinctually, that doesn’t mean that they usually do.
  2. B
    Insect behavior is exclusively Remaining source text redacted.
    Why choice B matches the stem
    This answer is supported by the stimulus. Insects are established as not having a sufficiently large brain to engage in flexible - or noninstinctual behavior. If that’s the case, then the only type of behavior they can engage in is instinctual.
  3. C
    All organisms with brains Remaining source text redacted.
    Why choice C is not credited
    While insects are noted as having brains that are too small to engage in noninstinctual behavior, they’re not established as being on the threshold. It could be that an animal needs a brain twice as big as an insect’s to have a brain sufficiently large to engage in such behavior.
  4. D
    All organisms with large Remaining source text redacted.
    Why choice D is not credited
    The key metric is the number of nerve cells. While insects are noted as having brains too small to possibly have enough nerve cells, there’s no indication that having a large brain guarantees a large enough number of nerve cells to engage in noninstinctual behavior. Additionally, the nerve cells are noted as being a requirement for noninstinctual behavior, so there could be other biological requirements for it.
  5. E
    Only organisms with brains Remaining source text redacted.
    Why choice E is not credited
    This answer is the flipside of (C) - it’s possible that a brain needs to be twice as big as an insect’s before it can potentially have enough nerve cells to allow for noninstinctual behavior.

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