PrepTest 125

Incorrect. The argument relies only on the sea snail in question being generally representative of sea snails, not that all sea snails react the same way. If there are a few weird sea snails out there that react to turbulence differently, that doesn't affect the argument.

Incorrect. It doesn't matter whether the light exposure is normal for sea snails, but rather how sea snails normally react to any such light that's relevant.

Incorrect. This answer addresses the sampling flaw we noted. However, it's too broad to be necessary for the argument. The stimulus relies on this sea snail being representative of other snails with how it reacts to light and shaking, not how it reacts to all external stimuli.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Necessary Premise

Stimulus Summary:
Sea snails - React to turbulence by tensing its foot.
Experiment - Shine a light while shaking a tank. Then, shine a light without shaking the tank.
Results - The sea snail tensed its foot during the light/shake combo, and then kept tensing its foot when just the light was used.
Conclusion - The sea snail learned to associate the light with shaking.

Answer Anticipation:
There's a lot of subtlety to this argument, but it deals with an experiment, so we should consider a sampling flaw and a correlation/causation flaw.

For the sampling flaw, the experiment appears to have been done with a single sea snail. While there's no reason to believe it's not representative, that's too small a sample to draw a broad conclusion about sea snails. The argument assumes that this snail has similar reactions to light/shaking as other snails, and to how it learns to associate stimuli.

For the correlation/causation flaw, it can be easy to think that one isn't present because there's a causal premise (sea snails typically react to ocean turbulence by flexing their feet) and the conclusion isn't causal. However, the argument is relying on the shaking of the tank causing the foot to flex in order to reach that conclusion—otherwise, it doesn't make sense to say that associating the light with shaking would explain why the snail is tensing its foot when just the light is flashed.

With that established, we can see that the argument is basing that on a correlation—the flexing of the foot being correlated with both shaking and shining the light. Since the argument, in concluding that the snails associated the light with shaking, believes that the shaking/turbulence is the true cause of the foot tensing, it's making a correlation/causation jump. That assumes that there isn't another cause—and, in this case, there's a clear potential alternative—the light itself. Maybe the snails react to bright lights by tensing their feet. If that's the case—and the evidence is at least as strong for that conclusion as the author's—then the argument falls apart. Let's find an answer ruling that possibility out.

Answer Explanation:
This answer rules out an alternative possibility—it's not that the snails associated bright lights with shaking, thus stimulating the tensing response. Rather, it's possible that the snail reacted directly to the light by tensing its foot—and if that's the case, the conclusion is unsupported. This answer rules that possibility out, which is necessary for the argument to hold.

Key Takeaway:
First, not all causality is explicitly stated, and some explanations require you to understand the implications of the conclusion instead of the conclusion itself. Here, the conclusion was about the association of the light to shaking, but the assumption was about the relationship between shaking and tensing.

Second, when an argument reaches a conclusion that assumes a certain explanation, it's necessary that alternative explanations aren't correct for that conclusion to be. As such, correct answers in Strengthen with Necessary Premise questions will frequently rule out an alternative explanation.

Incorrect. First, if anything, the reaction being learned rather than instinctual aligns more with the argument since the association in question is learned. That said, this answer doesn't really affect the argument at all. While the association between the light and shaking may have been learned, the reaction could still be instinctual.