Inference Questions: Wrong Answer Types

There are several different kinds of “inference questions” on the LSAT. Some are perfect examples of pure conditional reasoning, such as the “must be true” and “must be false” questions in logical reasoning and logic games. Others are “softer” inferences, such as the “most strongly supported” –questions in logical reasoning and the “author is most likely to agree” type statements in reading comprehension. There are important similarities between these different questions, and even more important similarities between the wrong answers to these questions.

In this post, we will look reading comprehension inference questions. These are functionally identical to the “most strongly supported” logical reasoning questions, with the added challenge of searching sixty lines of reading comp to find the answer instead of the typical six-to-twelve line logical reasoning stimulus. All that text means that a clever and imaginative student can conjure up some reason a wrong answer might be right. (I’ve seen it done… and I’ve even done it myself!) That is a problem for LSAT takers and for the people who write it. The LSAT authors always include the word “most” in phrases like “which of the following is most strongly supported” to respond to students who call up to complain that some other answer is arguably correct, but they don’t want to have that conversation. They want each wrong answer to be provably wrong–and there are only so many ways to do that. Learn that handful of “wrong answer techniques,” and you will get faster and better at inference questions.

Quantities and Comparisons

The easiest wrong answer involves a “quantity” claim that is not supported by the text. The easiest way to generate such an answer is to take a sentence that is clearly stated in the text and then add one “quantity word” that isn’t in the text. Thus, if the passage says “ultraviolet light causes skin cancer” don’t be surprised if you see a wrong answer that claims that “ultraviolet light is the primary cause of skin cancer.”

“Comparison words” are common in wrong answers, for several reasons. Consider an answer like “The diversity of plant species was greater in ancient forests than in modern forest.” For that to be the right answer, we will need information about the plant diversity in ancient forests, the plant diversity in modern forests, and some common unit of measurement that allows us to compare them. It isn’t enough to say “there were lots of plant species in ancient forests” and “modern forests have many different species.” That doesn’t tell us which has more. Comparison answers can be right, but only if there is clear and specific information to support it–and that is the exception, not the rule.

Sounds good but not supported

An answer is provably wrong if it includes an element that never appears in the passage. The LSAT authors must tempt test-takers to choose such an answer, so they often write an answer choice that appeals to the readers common sense or preconceptions. If your initial response to answer is “that is probably true,” be careful! The question before you is not “what is true” but “what is supported by the text.”