Identifying Assumptions on the GMAT

Do you find yourself with your head in your hands after yet another series of practice questions, looking at a less than 50% hit-rate on Assumption questions? You’re not alone! Most of us have no background with formal logic prior to the GMAT, and suddenly we’re expected to understand brand-new concepts like premise, conclusion, flaw, etc. intuitively. To start with, let’s review some basic definitions.

A conclusion is a statement based on other statements in the argument. Those “other statements” are the premisses (or collectively, the premise) of the argument.

An assumption is a specific kind of logical fallacy called a fallacy of presumption. The author is presuming something to be true which is unsupported or unwarranted. Generally it comes from a gap in logic between the premise and the conclusion. Imagine the author is crossing a river, leaping from rock to rock, trying to avoid getting wet. Each rock represents the pieces of evidence. The author hops from idea to idea, then takes a final, extra-big leap into the air (making his conclusion). The final stone below him is the assumption. If it’s there, it will support the author’s weight as he descends. If not, he falls into the river, and his conclusion doesn’t hold. An assumption covers the weakness of the conclusion. Let’s look at a sample CR question:

One of the best ways you can feed your brain for better memory is by avoiding a diet high in trans-fat and saturated fat. A recent study has found that these fats, such as those from animal products, can cause inflammation as well as produce free radicals, which tend to weaken the brain’s higher functions. Many meat producers, however, have pointed out that free radicals are a normal by-product of the body’s natural metabolism. Though this may be true, there is still sufficient proof that a better memory can be achieved by avoiding too much red meat.

Which of the following is an assumption upon which the argument depends?

(A) Free radicals in high-enough quantities can damage or kill brain cells.

(B) Memory is considered a higher brain function.

(C) The body’s metabolism does not also cause inflammation.

(D) No other fats increase inflammation and free radicals.

(E) The free radicals found in red meat are not found in other types of food products.