A recent study found that individuals who regularly consume blueberries score significantly higher on cognitive function tests than those who do not. Researchers concluded that eating blueberries enhances cognitive ability. Which of the following, if true, would most seriously weaken the researchers' conclusion?
- AA separate study found no significant difference in cognitive function between blueberry eaters and non-eaters.
- BCognitive function can be improved through various activities, such as reading and learning new skills.
- CBlueberries are rich in antioxidants, which are known to protect brain cells from damage.
- DThe study participants who ate blueberries also tended to exercise more frequently and eat a healthier diet overall.
Show answer & explanationAnswer & explanation
Correct answer: D. The study participants who ate blueberries also tended to exercise more frequently and eat a healthier diet overall.
The argument establishes a correlation between blueberry consumption and cognitive function, then concludes causation. To weaken this, one must introduce an alternative cause for the observed effect. Option A suggests that other healthy habits, rather than blueberries themselves, could be responsible for the improved cognitive scores.
Why the other options are wrong
- A. While a separate study finding no difference might cast doubt, it doesn't directly explain *why* the original study's conclusion is flawed, unlike identifying a confounding variable.
- B. This is general information about cognitive function improvement and doesn't directly address the causal link between blueberries and cognitive ability in the context of the study.
- C. This provides a mechanism by which blueberries *could* enhance cognitive ability, thus strengthening, not weakening, the conclusion.
Weakening an Argument
To weaken an argument means to introduce information that makes the conclusion less likely to be true, often by providing an alternative explanation for the observed facts or attacking an underlying assumption.
- Introduces alternative causes.
- Challenges the validity of evidence.
- Attacks underlying assumptions.
Memory trick: Weak arguments crumble with alternative causes or flawed foundations.