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To Diagram or Not to Diagram? That is the (LSAT) Question.

matt_diagramming1Shakespeare had it all wrong. For aspiring and motivated LSAT students, there is a different question that dominates their consciousness, especially during the early part of their studies: to diagram or not to diagram?

Diagramming is a term that has been coined for actually taking the time to map out the logic involved in a logical reasoning question. For instance, the sentence “If Shakespeare wanted to be understood, he would have written in plain English” can be diagrammed as: SU→PE. The idea is that the diagram can help students to understand the logic of the statement and to ultimately find the correct answer choice. However, this new step tends to bring much frustration for students when they first begin to practice it.

This is indicative of a difficulty most students confront when studying for the LSAT. When you begin to formalize your studies (most notably if you take a prep course), the first thing that we do for you is that we make the test more complicated. When you first take a practice test, you just do things your way. Unfortunately, your way does not work (hence the 132 score and the overwhelming desire to drink).

Diagramming is a prime example of this phenomenon. It is inevitably confusing for students at first because you are attempting to translate between the English on the page and the logical symbolism that you probably don’t really understand well.

However, this initial complication is necessary. Have you ever taken a golf lesson? You have to think through all kinds of details to produce a good swing—from the position of your hips, to your elbow angle, to your follow through. The result is that while you probably initially hit the ball okay, for your first several lessons you’re probably missing the ball entirely. But stick with it and your swing will improve and soon you will be far better than you were before you took lessons. You also may have to purchase a pair of plaid pants and a ridiculous beanie. But that’s beside the point.

The above phenomenon is true of the LSAT, too. Learning to diagram conditional statements is a necessary step in your improvement (we have some more general advice about logical reasoning up here). Without it, your score probably won’t increase as much as it could. But master diagramming and you will become a better test taker.

When I tell students that I still diagram a number of logical reasoning questions, they tend to not believe me. They must think that this is just some sort of crap that we developed to fill the time between breaks in class. But that is not the case. I actually believe that there are a handful of questions on every LSAT that you cannot get correct without being able to accurately diagram, and there are another handful on which it is very helpful. I also think that diagrammable questions can be a big confidence boost in the middle of a section. Many questions on the LSAT will not be black and white for you on game day. Rather, you will always have lingering doubts. Maybe C was better? I could have misread something and D could have been right? That is natural. But questions where you diagram should not leave any room for doubt. For instance, if you are doing a Must Be True question, and the stimulus reads:

    No one who owns a speedboat will become the President of the United States.
    Everyone who lives in Alabama and is over 35 owns a speedboat.

This is a relatively simple example, but a good LSAT student would diagram this question as follows:

    Speedboat → Not President
    Alabama and Over 35 → Speedboat

This leads to the conclusion that anyone who lives in Alabama and is over 35 will not become President. Shocking. So if we see an answer choice that says the next President of the United States will not be someone from Alabama who is over 35, we would quickly pick that answer and know that we have been given the contrapositive in the correct answer choice. But the important part is that we should not have any doubt that we have found the correct answer. For once, you can see it. With practice, it can be like concluding that 2 + 2 = 4. And that can be nice in the middle of this grueling test.

So here is why I decided to write about this—not only to stress the importance of practicing diagramming, but also to give you some tips on when to do it. One of the hurdles that students run into early on when they are working through logical reasoning is that they cannot decide when to diagram and when not to diagram. For Must Be True and Must Be False questions, you want to diagram about half of the time. For other question types, diagramming occurs less frequently but can also provide a significant advantage.

In general, you want to diagram the stimulus to a logical reasoning question when it will help you identify the correct answer choice. But how do you know? Well, there are a few helpful hints. First, you want to make sure that you have at least one real conditional statement in the stimulus. I find that students attempt to diagram a lot of statements that are not really conditional statements. You can always test to see if you are dealing with a conditional statement by playing with the parameters of the statement.

    Every time Rachel goes to the mall, she buys a new dress.

Does one thing guarantee something else? Yes, going to the mall guarantees that Rachel buys a new dress. So this is a conditional statement.

    Because of the recent recession, the Rodriguez family has to move.

Does one thing guarantee something else? Well, no. This recession might have caused the family to move. But we don’t know that every recession makes people move. So this is not a conditional statement. This is just explaining to you why something happened.

You can also use certain key words to identify when to diagram. Words like every, any, all, only, and unless are good hints that you are dealing with a conditional statement.

The second key for students is even more important: if you are going to diagram, you need to know that taking the time to diagram will actually lead to some logical conclusion. How do you know? You should only take the time to diagram a question if you have the same term that is used in two different conditional statements.

    Until 1976, no responsible veterinarian performed experiments that would lead to the death of innocent lab animals. Since 1990, the practice has become more common and many highly-trained veterinarians have commenced to use lab animals for experiments even if they could lead to the death of the animals, but only if the experiments could contribute to the development of life-saving technologies for humans.

This might be a question that students would be tempted to diagram. We definitely see some key words, like “no” and “only if”. But it would not be helpful to diagram this question. In fact, it would probably cause you to waste time and get the question wrong because you would be focusing on the diagram rather than the big picture. But here you should note that there is nothing in common between the two statements. The terms are all different. We have ‘responsible veterinarians’ and ‘highly-trained veterinarians’ and we have ‘would not perform experiments’ and ‘will perform experiments but only if they lead to important discoveries’. But that means there will be no way to combine the statements to get anywhere. For a question like this, you would be much better just summarizing the question by saying that ‘vets are loosening up on animal testing as long as it has good benefits for humans’.

The following is an example of a statement that should be diagrammed.

    All the students in the class understand Shakespeare. You cannot understand Shakespeare unless you buy CliffsNotes or bribe the TA to tutor you personally.

Anytime you see a structure like this, or anything where the same term pops up in two statements, that means is is time to diagram. And here we could draw the conclusion that all the students are buying CliffsNotes or bribing the TA. And that is going to get you the correct answer.

So, to review, make sure the stimulus meets two requirements before you diagram:

    1. The statements are conditional statements, not just a description of a state of affairs; and
    2. There is at least one term in common between the statements so you might be able to combine them.

And stick with it. At first, it seems complicated, but I promise it gets better. If you don’t diagram, you are just setting yourself up for a low score, and parting with a good LSAT score is such sweet sorrow.