LSAT (Law School Admission Test)Logical ReasoningMedium
A medical researcher claims: 'Our new drug, 'Cognito,' significantly improves memory function in elderly patients. In a clinical trial, patients who received Cognito showed an average 15% increase in their scores on standardized memory tests, whereas patients in the control group showed no significant change.' Which of the following, if true, would most seriously weaken the researcher's conclusion?
- APatients in the Cognito group were also encouraged to perform daily mental exercises, which can improve memory.
- BThe control group received a placebo, and its members were unaware they were not receiving Cognito.
- CThe memory tests used in the trial were not specifically designed for elderly patients.
- DOther memory-enhancing drugs on the market show an average improvement of 20% in similar trials.
Show answer & explanationAnswer & explanation
Correct answer: A. Patients in the Cognito group were also encouraged to perform daily mental exercises, which can improve memory.
The researcher concludes that Cognito *causes* improved memory. Option C introduces an alternative cause (mental exercises) for the observed improvement in the Cognito group, making it unclear whether the drug or the exercises (or both) were responsible, thereby weakening the causal conclusion.
Why the other options are wrong
- B. This describes a well-designed aspect of a clinical trial (placebo-controlled, blinded), which strengthens, rather than weakens, the validity of the comparison.
- C. This might suggest the tests are less sensitive or less relevant, but it doesn't directly weaken the claim that Cognito *caused* the observed improvement, only perhaps the significance of that improvement.
- D. This compares Cognito's effectiveness to other drugs, but does not weaken the claim that Cognito *itself* significantly improves memory function.
Alternative Cause (Causal Flaw)
A flaw in reasoning where an argument attributes an effect to one cause, but there is another plausible factor that could also be responsible for the observed effect.
- Challenges the uniqueness of the proposed cause
- Often involves a 'confounding variable'
- Weakens a causal conclusion
Memory trick: Look for another chef in the kitchen!