Question

Although migraine headaches are believed to be caused by food allergies, putting patients on diets that eliminate those foods to which the patients have been demonstrated to have allergic migraine reactions frequently does not stop headaches. Obviously, some other cause of migraine headaches besides food allergies must exist. Which of the following, if true, would most weaken the conclusion above?

• A. Many common foods elicit an allergic response only after several days, making it very difficult to observe links between specific foods patients eat and headaches they develop.
• B. Food allergies affect many people who never develop the symptom of migraine headaches.
• C. Many patients report that the foods that cause them migraine headaches are among the foods that they most enjoy eating.
• D. Very few patients have allergic migraine reactions as children and then live migraine-free adult lives once they have eliminated from their diets foods to which they have been demonstrated to be allergic.
• E. Very rarely do food allergies cause patients to suffer a symptom more severe than that of migraine headaches.

Hint:

To weaken a conclusion in a Critical Reasoning question, look for an answer choice that attacks the assumption linking the premise to the conclusion. Often, this involves providing an alternative explanation for the evidence presented in the premise.

Answer 1

The Correct Option is A

Step 1: Understanding the Argument:
- Premise: Eliminating foods to which patients have a *demonstrated* allergic reaction often doesn't stop their migraines.
- Conclusion: Therefore, there must be some other cause for migraines besides food allergies.
- Task: Weaken the conclusion. This means we need to find an answer that suggests food allergies *could still be the sole cause*, despite the failure of the elimination diet mentioned in the premise.
Step 2: Analyzing the Argument's Logic and Finding the Gap:
The argument assumes that the "demonstrated" allergic reactions are the *only* relevant allergic reactions. The conclusion (that another cause must exist) relies on the premise that the elimination of known allergens was complete and accurate. If we can show that the process of "demonstrating" or identifying the allergies is flawed, we can argue that the diet failed not because the theory (allergies cause migraines) is wrong, but because the application (the diet itself) was incomplete.
Step 3: Evaluating the Options:
(A) Many common foods elicit an allergic response only after several days, making it very difficult to observe links... This directly attacks the gap in the argument. It suggests that the process of "demonstrating" which foods cause an allergic reaction is difficult and likely incomplete. If patients are still unknowingly consuming other trigger foods because the allergic reaction is delayed and hard to pinpoint, then the diet would fail even if food allergies were the only cause. This provides an alternative explanation for the premise and seriously weakens the conclusion that there *must* be another cause.
(B) Food allergies affect many people who never develop the symptom of migraine headaches. This is irrelevant. The argument is about people who *do* get migraines, not those who don't.
(C) Many patients report that the foods that cause them migraine headaches are among the foods that they most enjoy eating. This might explain why patients find the diet difficult, but it doesn't weaken the conclusion about the cause of migraines.
(D) Very few patients have allergic migraine reactions as children and then live migraine-free adult lives once they have eliminated from their diets foods... This describes a group for whom the diet works. If anything, this slightly strengthens the idea that for the other group (in the premise), there might be another cause. It doesn't weaken the conclusion.
(E) Very rarely do food allergies cause patients to suffer a symptom more severe than that of migraine headaches. The severity of symptoms is not relevant to the cause of the headaches.
Step 4: Final Answer:
Option (A) provides the strongest reason to doubt the conclusion by showing that the premise (the failure of the diet) does not necessarily lead to the conclusion (another cause must exist).