Logic Games Inferences, Demystified


Manhattan Prep LSAT Blog - Logic Games Inferences, Demystified by Ally Bell

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Doing a practice logic game on the LSAT can often feel like watching an episode of Sherlock. I usually think I’m following the show pretty well—until I get to the end and Sherlock unravels all the clues I should’ve seen along the way. Similarly, when we do logic games, it often seems like things are going fine, but when we check our work against a master diagram, there are all sorts of magical Logic Games inferences that we wish we had made earlier!

That’s especially true when it comes to what I call up-front inferences, or the Logic Games inferences that you make while setting up your diagram but before answering the questions. So how can you become a Sherlock at up-front inferences? Here are a few tried-and-true tips.

1. Know which games have a lot of up-front inferences, and which don’t.

Relative ordering games and in/out games typically don’t offer a lot of inferences in your setup. Instead, you do most of the legwork at the question level. But for any game that requires you to set up a number line (basic ordering, 3D ordering, mismatch ordering) or a board (open grouping, closed grouping, 3D and hybrid grouping) there will be more opportunities for up-front inferences.

2. Use the 3-pass system.

Inferences come from rules interacting with each other. To make sure I catch ‘em all Pokemon-style, I always make at least three passes through the rules. The first time, I make sure I’ve diagrammed everything correctly and put what I can on the board. The second time, I check each rule against everything I’ve already diagrammed, seeing if I can make any new connections. If I’m able to put something new on my diagram, that may interact with even more rules! So I do a third pass to see if I can get even more inferences. I keep going until scanning the rules stops yielding any new info.

3. Ask the right questions.

When I’m setting up a diagram, I’m constantly asking myself the same questions as I eyeball each rule:

“If I follow this rule, can I figure out where any letters cannot go?”
“Can I figure out where any letters must go?”
“Do the letters/spaces in this rule show up anywhere else?”
“What’s left that could go in this space? What spaces are left for this letter?”

4. Write EVERYTHING down.

Sometimes, an inference seems so obvious that it doesn’t seem worth writing down. Of course you’ll remember it, right? Wrong. Your brain is juggling a million pieces when you do the LSAT, so don’t leave anything to chance. If you figure out that K can’t go in 1, write it down!

5. Look for pile-ups.

The bottom of my board is usually where I cross out letters that can’t go in certain slots or columns. When multiple crossed-out letters start to pile up under one slot, I start thinking about what letters can go in that space. Sometimes, I’ll get it down to just two or three letters, and then I can put them on the board with slashes or a cloud.

6. Know what you know and what you don’t know.

People often get in trouble here because they run out of inferences, so they just start trying things out on the board. That can be a useful way to get yourself “unstuck,” but you have to be very careful with it. You shouldn’t put anything that you don’t have firm information about on the board as just a “test.” Make a separate board for that! If you know generally where some letters go but can’t pin them down to one spot, use a cloud (a circle above the board) to indicate where they could go.

7. Ask yourself if frames would be helpful.

Framing a diagram means making 2-3 possible diagrams based on a clear split in the rules, or one that shows up in your inferences. For example, maybe H can go in 2 or 4, and if you could figure that out, lots of other letters would fall into place. If you see a fruitful opportunity for frames, go for it! Frames are often a key solution for tricky set-ups that don’t seem to offer many inferences.

8. Know when to stop.

If you are methodical about inferences (perhaps using the 3-pass system mentioned above), you’ll reach a natural stopping point when you don’t see any more new connections. At this point, ask yourself if you see any opportunities for frames, whether there are any letters missing from your diagram, and refresh yourself on which rules will be most important. Then move onto the questions!

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Ally Bell is a Manhattan Prep Instructor who lives in the Washington, DC metro area. Ally first encountered the LSAT while getting her Bachelor of Arts in English and history at Duke University. In college, she scored a 178 and very nearly applied to law school. In the end, she followed her true passion, teaching. Ally currently has the pleasure of being an eighth grade English teacher in Northern Virginia. As an LSAT teacher, she has the opportunity to blend her love for teaching with her passion for logical argument. Check out Ally’s upcoming LSAT Complete Courses here.

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