GMAT Focus EditionVerbal ReasoningMedium
A recent study found that individuals who regularly consume fermented foods, such as kimchi and yogurt, have a lower incidence of anxiety and depression. Researchers concluded that the probiotics in these foods positively impact gut-brain axis communication, thereby improving mental health. Which of the following, if true, would most strengthen the researchers' conclusion?
- AFermented foods are often part of a generally healthy diet, which itself is linked to better mental health.
- BParticipants in the study who consumed fermented foods also reported higher levels of social support.
- CThe study controlled for other lifestyle factors known to influence mental health, such as exercise and sleep.
- DA separate study found that individuals with diagnosed anxiety disorders often have an imbalanced gut microbiome.
Show answer & explanationAnswer & explanation
Correct answer: C. The study controlled for other lifestyle factors known to influence mental health, such as exercise and sleep.
The researchers conclude a causal link between probiotics in fermented foods and improved mental health via the gut-brain axis. Option C strengthens this by ruling out other common factors (exercise, sleep) that could independently explain the improved mental health, making the link to fermented foods more specific and robust.
Why the other options are wrong
- A. This identifies a confounding variable (overall healthy diet), which would *weaken* the conclusion that fermented foods specifically are responsible.
- B. Higher social support is another factor linked to better mental health, acting as a confounding variable that would *weaken* the researchers' conclusion about fermented foods.
- D. This suggests a correlation between gut health and anxiety, which supports the broader idea of a gut-brain link, but doesn't specifically strengthen the claim about *probiotics in fermented foods* causing the improvement.
Strengthening Causal Claims by Eliminating Confounders
Bolstering a causal argument by showing that other potential influencing variables (confounding factors) have been accounted for or minimized.
- Increases confidence that the observed effect is due to the proposed cause.
- Reduces the possibility of alternative explanations.
- Often involves experimental controls or statistical adjustments for known variables.
Memory trick: Clear the fog around the path to see the true direction.