GMAT Focus EditionVerbal ReasoningMedium
A recent study found that individuals who regularly consume fermented foods, such as yogurt and kimchi, exhibit lower levels of perceived stress and anxiety. The study authors concluded that increasing fermented food intake in the diet can effectively reduce psychological stress. Which of the following, if true, would most strengthen the study's conclusion?
- AThe study participants who consumed fermented foods reported higher overall life satisfaction, independent of stress levels.
- BMany individuals who consume fermented foods also engage in regular exercise, which is known to reduce stress.
- CA separate double-blind, placebo-controlled trial showed that participants given probiotic supplements derived from fermented foods reported significant reductions in stress markers.
- DSome fermented foods contain high levels of sodium, which can have adverse health effects if consumed excessively.
Show answer & explanationAnswer & explanation
Correct answer: C. A separate double-blind, placebo-controlled trial showed that participants given probiotic supplements derived from fermented foods reported significant reductions in stress markers.
To strengthen a causal conclusion, evidence must be provided that directly links the cause (fermented foods) to the effect (reduced stress) while minimizing the influence of other factors. Option B provides such evidence through a controlled trial, directly supporting the causal link.
Why the other options are wrong
- A. This suggests an alternative explanation for the observed correlation (overall life satisfaction leading to both fermented food intake and lower stress) rather than strengthening the proposed causation.
- B. This introduces a confounding variable (exercise) that could also explain the reduced stress, thereby weakening or failing to strengthen the conclusion.
- D. This points out a potential negative aspect of fermented foods, which is irrelevant to whether they reduce stress and thus does not strengthen the conclusion.
Strengthening a Causal Claim
Providing additional evidence that directly supports a cause-and-effect relationship, often by ruling out alternative causes or showing a plausible mechanism.
- Directly links cause to effect.
- Reduces the likelihood of confounding factors.
- Can involve showing a mechanism or independent corroboration.
Memory trick: Connect the dots, prove the mechanism, control the variables.