If you’ve spent any length of time studying the Logic Games section of the LSAT, you’ve probably realized that deductions (or inferences, as you may call them) can make or break a game. Sometimes they’ll simply help you get through a game more quickly; sometimes you won’t even be able to answer a question without having caught the deduction.
So deductions are, to put it lightly, important. Unfortunately, they can also be tricky to spot. When working through a game, after building the setup and representing rules, here are a couple of good areas to start your search for deductions:
1) Extremely restrictive rules
If a rule strongly limits where a player can go, that’s a good spot to start looking for deductions. In ordering games, for instance, what we at Blueprint LSAT call “blocks” can be very helpful when looking for deductions (e.g. “Namboko and Quilong are separated by exactly one person”). These types of rules also frequently lead to “scenarios,” in which there are a severely limited number of ways a game can work (say, only two places where that block can go); in those cases, it’s worth your while to make a quick hypothetical for each scenario, which will often lead to additional deductions.
2) Rules that interact with each other
You’re unlikely to find a deduction by looking at a single rule. However, if two or more rules interact in some way (most often by having a player in common), that’s a lot more likely to lead to deductions. When setting up a game, I’ll look over the rules to see whether any of them discuss the same player and, if so, what happens when you combine those rules.
Finding deductions is a skill and, like any other skill, it takes a lot of practice. In order to train your brain to look for deductions, I recommend spending some of your study time doing the setup for an individual game, and then spending as much time as possible looking for deductions and scenarios until you’re positive you’ve found everything that can be found.
At that point, stop and look at an explanation for the game – for Blueprint students, I recommend watching the homework video explanation for that question, but if you’re using a different study method (it’s ok, we’ll forgive you) then you can just check out whatever explanation is available to you. If the explanation has deductions or scenarios that you didn’t notice, your job is to figure out why you missed those deductions the first time around. The idea, of course, is that you’ll start to get a better sense of what rules lead to deductions, and how to spot them – and soon you’ll become a deduction-finding machine.