Passage Summary: Mice on ginkgo did better on memory tests, but the author thinks it's because the ginkgo calmed them down, not because it actually boosted their brainpower.

Conclusion: Ginkgo extract might improve memory indirectly by reducing stress rather than by directly enhancing cognitive function.

Reasoning: While ginkgo-fed mice showed better memory, ginkgo is known to lower stress, and lower stress is already known to improve recall.

Analysis: The author is trying to replace one cause (direct memory boost) with another (stress reduction). To weaken this, we need to show that the stress reduction wasn't the actual factor in this specific experiment. For example, if the mice in this study weren't stressed to begin with, the stress-reduction explanation falls apart. Look for an answer that disconnects the stress-reduction benefit from the mice's performance.