GMAT Critical Reasoning questions often ask you to weaken, strengthen, or identify an assumption in an argument. A systematic logic-chain approach helps you break down the reasoning and spot the gap between evidence and conclusion. This article summarizes common techniques and walks through official examples to show how the method works.
Understanding the Logic Chain
Every GMAT argument consists of premises (facts or evidence) and a conclusion. The logic chain is the reasoning that connects them. Your first step is to identify these parts. Then, ask: does the evidence actually lead to the conclusion? The gap is where the argument is vulnerable.
For weaken questions, you attack the link. For strengthen questions, you reinforce it. For assumption questions, you identify what must be true for the conclusion to hold.
Weaken Questions: Breaking the Link
Consider this official-style example:
Argument: “A new medication reduces blood pressure. Therefore, it will lower the risk of heart attacks.”
Logic chain: reduced blood pressure → lower heart attack risk.
To weaken, you need to show that the link does not hold. For instance: the medication reduces blood pressure only temporarily, or it has a side effect that increases clotting. You are not disproving the premise; you are attacking the conclusion based on the evidence.
Common weaken strategies:
- Introduce an alternative cause for the observed effect.
- Show that the evidence is unrepresentative.
- Demonstrate that the effect would occur regardless.
- Reveal a flaw in the data or methodology.
Strengthen Questions: Solidifying the Link
Using the same argument, a strengthener would support the idea that lower blood pressure indeed reduces heart attack risk. For example: “Studies show that patients with similarly reduced blood pressure had fewer heart attacks.” Or: “The medication’s mechanism directly repairs arterial damage.”
Strengtheners often:
- Eliminate alternative explanations.
- Provide additional evidence that the cause-effect relationship holds.
- Confirm the reliability of the data or study.
Assumption Questions: Filling the Gap
Assumptions are unstated premises that the argument needs. In the blood pressure example, a necessary assumption is: “Lower blood pressure is sufficient to reduce heart attack risk.” If that assumption were false, the argument collapses.
When identifying assumptions:
- Ask: what must be true for the conclusion to follow from the evidence?
- Use the negation test: negate the assumption; if the argument fails, it is correct.
Applying the Logic-Chain Method: Step by Step
Let’s work through another official-like question.
Argument: “Company X’s profits increased 20% after hiring a new CEO. Clearly, the CEO’s leadership caused the profit increase.”
Logic chain: new CEO → increased profits.
Weaken: Show that other factors, such as an industry boom or cost-cutting measures already in place, explain the increase.
Strengthen: Show that the CEO implemented successful strategies, and no other major changes occurred.
Assumption: The new CEO’s actions were the sole cause of the profit increase, and no external factors contributed.
Common Pitfalls and Tips
- Don’t confuse weakening the premise with weakening the argument. The premise is accepted as true; you are challenging the reasoning.
- Watch for out-of-scope answer choices. They may seem related but do not affect the logic chain.
- In assumption questions, extreme language (always, never) is often not required; necessary assumptions can be moderate.
- Diagraming the logic chain on scratch paper helps visualize the gap.
FAQ
What is the negation test for assumption questions?
Take the answer choice and negate it (turn it into its opposite). If the negated statement makes the argument fall apart, then the original is a necessary assumption. For example, if an assumption is “All employees are trained,” negated as “Not all employees are trained,” and the argument relies on training, the argument fails.
How do I quickly identify the conclusion in a GMAT argument?
Look for indicator words like “therefore,” “thus,” “so,” “clearly,” or “hence.” The conclusion is the main point the author is trying to prove. Sometimes it appears at the beginning or end of the stimulus.
Are there any official GMAT resources for more practice?
Yes, the GMAT Official Guide and GMAT Official Advanced Questions provide numerous Critical Reasoning questions with explanations. Using real questions is the best way to master these techniques.