Monday, August 16, 2010

Logical Reasoning Assumption: Definition Shift

For today we'll tackle another frustrating--but thankfully rare--logical reasoning task, definition shift assumption. All test prep companies have their own take on how to spot assumptions, but as per usual, here at Zen of 180 we have a slightly more discriminating classification system. There are four types of assumption questions on the LSAT; definition shift requires a level of detail in your reading that borders on obsessive compulsive disorder.  

From the stimulus' evidence to its conclusion, a key term will shift in some meaningful way that is not readily apparent to the average reader--even the average LSAT reader.  While such shifts occur on a daily basis in nearly all forms of non-LSAT communication, such shifts can mean the difference between absolutely right and wrong.

Thus, the answer in a definition assumption task will be an "LSAT speak" link between the two terms, one from the evidence and the other either in the bridge or the conclusion.  It seems easy enough, but the answer thus also looks like a common distractor for all the other assumption tasks!

The difference between prephrasing the gap and prephrasing the answer is similar to saying, "I need to get across the river here" and "I need to drive across the one-lane wooden bridge." The former prephrase will allow you to consider any answer that accurately links across the--in this case literal--gap, while the latter will be too specific for many test takers to find the credited response translated into LSAT speak.

At first blush, such distinctions between executive boards and Executive Directors or between gaps and answers can appear to be inconsequential; however, the LSAT gets plenty of test takers to gloss over a crucial definition shift between evidence and conclusion. This test is not kind to careless readers, and the specificity of language employed is very different from everyday language.

The example from the June 2007 sample PrepTest is a perfect example of that required level of specificity, which is where our "executive" by line comes from.

The question stem for this strand is fairly easy to identify, and since definition shift assumptions are so rare, be sure to first approach them as you would a definition assumption task.  Actively read the stimulus for the conclusion, the key evidence, and then fact-check the conclusion to find disparities between the two.

We're in the process of analyzing the older PrepTests for the different assumption tasks, but we do know how often it has been asked on modern LSATs. It averages 0.6% of the points on a modern LSAT, and most PrepTests do not have any definition shift assumptions.
    3 times
    on LSATs since 2007
    0.6% of LR
    (0 per LSAT, range 0-1)
    ?% growth from pre-2007
We'll update this page after we're through analyzing all the older PrepTests for this particularly tricky assumption task.  Meanwhile, always keep an eye out for the shifts in definition for your assumption!