No matter how good you get at Logic Games, finding those difficult inferences will always be a challenge! In our “You Derive Me Crazy” blog series, we’ll take a look at some of the higher-level inferences that repeat on the LSAT, ensuring that you have all the tools necessary to tackle anything the LSAT throws at you on test day!
Some of the biggest inferences in Logic Games come in the form of frames — 2–3 skeletons that represent every possible way the game can work out. Here at Manhattan Prep, we have two questions that both need to be answered ‘yes’ before we consider frames:
- Is there a 2-3 way division in the game? This lets you know if it’s possible to build frames.
- Will each of those divisions have consequences? This lets you know if building the frames will be worthwhile.
Again, you need a ‘yes’ answer to both questions before it’s a good idea to build frames!
For the first question — is there a 2–3 way split? — each game type has rules that lend themselves to framing. Today, we’re going to talk about Grouping games.
We first have to split Grouping games into two main categories. These two categories largely align along how many groups we’re dealing with: two, or more than two. Two-group games (generally, In and Out) are a bit different because telling me that an element isn’t in one group necessarily means that it’s in the other. For this reason, we can use a different tool – the Logic Chain*, for those who are in the Manhattan Prep class – than we would for a “larger” grouping game.
So what type of rules lead to frames in two-group Grouping games?
Much like Relative Ordering games (ones where all the rules are relative ordering rules), most of the inferences come from correctly diagramming each of the rules, and combining them together.
However, there are a couple exceptions:
1) If there is a biconditional, or an “at least one, but not both” rule, then you can usually build frames around that rule.
2) If you’re in a game with element subsets (“There are three monkeys – F, G, and H – three raccoons…”), and one of the three groups is severely limited (“You have exactly one monkey”), then you can usually build frames around that rule.
If you don’t see one of those two types of rules, however, skip frames and head right into the questions.
What do both of those types of rules have in common? Same as in Ordering games, they’re especially restrictive. Looking at the “strongest” rule for frames is generally a good idea.
So what about those Grouping games with more than two groups? We’re going to look at similarly strong rules:
1) Biconditionals – Build a frame where both elements of the rule happen, and where both don’t. Those are the only two ways a biconditional can work out.
2) Must be Together – If you know two elements have to go together, try out a frame with the two lovebirds in each group.
3) One element, many rules – If you see a single element show up 3 or 4 times in the rules, try to place that element in each group and see what happens.
And, in a very special case:
4) If you’re in an Open Grouping game (one where you don’t know the size of each group), and a rule creates a strong relationship between the size of some of the groups (“Exactly twice as many people drink Kool-Aid as drink Hi-C”), then build frames around the group sizes.
Is this an exhaustive list? Nope. There are other cases that are a bit weird (Mauve Dinos, anyone? Build frames around what can be mauve). But if you always look at these rules when considering frames, you’ll be in great shape for getting through the test quickly.
*These games also have to have almost all conditional rules to use this tool, but that’s a distinction for another day.
Matt Shinners is a Manhattan Prep instructor based in New York City. After receiving a science degree from Boston College, Matt scored a 180 on his LSAT and enrolled in Harvard Law School. There’s nothing that makes him happier than seeing his students receive the scores they want to get into the schools of their choice. Check out Matt’s upcoming LSAT courses here!