GM Prep is a complicated topic that impacts how games are designed and how they’re played. There is a lot of “folk wisdom” related to classically structured RPGs and what should or shouldn’t be prepped, and a lot of interesting new games like Apocalypse World make what is or isn’t prepped by the GM a big part of the game design. I want to look at the topic from the psychological perspective of how different types of GM prep affect the GM and players of RPGs and how it shapes their subjective experience of playing.

I’ve blogged before about the psychological compliance technique of commitment and this is a big part of the GM prep picture: when a GM preps something for a game they make a commitment to contribute what they prepped to the fiction during play. This is very useful in a lot of RPG designs, because the psychological pressures on a GM during play (high cognitive load from keeping track of lots of details, face to face with the players, etc.) are different from those faced during prep. A good game designer will take into account which decisions they want the pre-play GM’s mind to make (and stick to) and call for prep that results in those decisions. This can be a way to get the game to introduce what Vincent Baker calls “unwelcome content”. Humans tend to make different decisions when framing them in short term or long term contexts. Most dramatic stories benefit from emotionally hard-hitting events and most games about challenge benefit from including genuinely dangerous obstacles. It’s frequently valuable to have these decisions made by the more cerebral pre-play GM than the one who is looking his sympathetic players in the eyes and might be tempted to pull punches. By using the principle of commitment, a game designer can get the GM to introduce content that might be uncomfortable in the short term but will provide a bigger long-term payoff (e.g. a more dramatic story, a more impressive victory, etc.).

A story from actual play: When I first tried to GM Mouse Guard, I tried to do it in what is popularly referred to as the “improv style”, i.e. I prepped almost nothing and intended to introduce the obstacles faced by the players on the fly. Although the game seemed to function, it was a totally unsatisfying experience for me as a GM. I felt like the players weren’t accomplishing anything – I was psychologically attributing their successes to my belief that I started throwing them softballs after taking sympathy on their early struggles. I decided to abandon that approach and switch to a strongly prepped game: I decided before each session what situations they’d face that would call for skill rolls, whether I’d be applying conditions or twists if they failed, and what those twists would be. The difference was night and day: by making these decisions before the game, I knew with complete confidence that what the players were or weren’t accomplishing was coming from them, not me, so I could be excited and enjoy their successes, commiserate with their troubles, and appreciate the gravity of their sacrifices – I could be a fan of the players rather than feeling like I was patronizing them.

So GM prep clearly has benefit for some games. Are there downsides? Let me talk about “railroading”. Railroading is when the GM plans for a certain sequence of events to happen, and uses subtle or overt manipulation or negation of player’s fictional contributions to cause those events to happen as originally planned. “Which way do you go?” “We go north.” “You get lost and circle around for a while, eventually ending up back where you started. Which way do you go?” “East?” “You go east for a while and enter a forest clearing just in time to see…” The GM is so committed to a certain element of fiction being introduced that other fictional contributions get stomped on. Why is this bad? Primarily because many games also rely on the principle of reciprocation to build investment in the fiction and game system. It’s OK for me to introduce content that might seem unwelcome because you know you’ll have a chance to respond and introduce your own content. If the players realize that their contributions are either being explicitly or implicitly ignored, then the principle of reciprocation stops working — since they’re not really getting a chance to say something that the GM must respond to, the GM has fewer psychological incentives working to get the players to accept the GM’s fictional contributions (in the classic railroading horror stories the GM ends up relying completely on authority).

What about less overt railroading? Here’s a hypothetical situation: we’re playing a classical “party of adventurers confronts dangerous situations” RPG. As GM, I prep a series of exciting set-piece battles, culminating in a dramatic showdown with the villain on a rope bridge over a river of lava. But, during play, the players decide they want to go to the ice realm instead of the fire realm. Thinking quickly, I reskin the encounter to take place on a bridge over a river of ice-cold water instead. Is this a problem? My answer is that it’s a lesser problem than explicit blocking of contributions, but it’s still a problem because of the frame of mind it puts the GM in: you’ve decided that the player’s contributions determine nothing but meaningless color. And by making the fire snow “meaningless” in your own mind, you undercut some of the value of your prep: you have no commitment to the fictional details of the situation, which will make it harder for you to engage with the fiction that’s happening in the game and increase the odds that you (and likely everyone else) will have a flatter, less satisfying gameplay experience.

The classic overreaction to the problem of railroading is to abandon prep entirely. As I’ve already explained, though, GM prep can be incredibly valuable. The trick is to figure out what kind of prep is right for the game you are playing. On his blog recently, Vincent Baker has been talking about the idea of “open” vs. “closed” questions in a game. When everyone is on the same page about which questions are going to be determined in-play, then there’s no risk of squishing those opportunities for fictional contributions by doing “bad” prep. Different games leave different questions open. In Dogs in the Vineyard, for example, the GM decides that there are mutually incompatible desires between NPCs in a town. There’s really never an opportunity to do an “It was all just a big misunderstanding!”ending in DITV, or have a “Can’t we all just get along?” plea really succeed. Somebody will be unhappy by the time the PCs decide to leave town (and maybe it will be the PCs). If the players came into the game expecting that they’d be able (with enough cleverness and skill) to achieve an everybody-wins solution, then the prep the GM did would likely conflict with that expectation. Once everybody’s on the same page about understanding what sort of the problems exist in DITV towns, though, the game tells the GM explicitly not to plan for a particular solution – players deciding what to do about the problems in the town is what the gameplay is all about, and most of the fun of GMing DITV comes from seeing the players interact with the situation in a way that’s unique to the people you’re playing with and the characters they chose to play.

Some people believe that the only solution to avoiding railroading is to abandon the idea of plot altogether. DITV and some other games solve the problem of achieving a satisfying story without railroading by guaranteeing how a story will proceed (for DITV, it’s in a series of emotionally and morally charged conflicts, in Apocalypse World it’s in a series of gritty situations, etc.) but not where the story will go. For some stories, such as character dramas, this is a great approach. It’s not ideal for all stories, though: some genres have strong expectations about how the plot will proceed. My own game Final Hour of a Storied Age is about Epic Fantasy stories, and I think that genre has strong requirements for how the overall plot happens, so I included a strong plot outline mechanic in the game (however, Storied Age is also GM-less and has no pre-session prep). I also recently participated in a playtest of Boarsdraft by J.B. Mannon which models the Harry Potter novels, so it has a heavy requirement for an overarching mystery plot that lasts the entire school year. These games are up-front about the overarching plot, so there isn’t any confusion about whether that’s an open question or not. In my opinion, pinning down the overarching plot is a design decision that lets you leave other questions open: not will you get there, but how. That doesn’t mean that pre-deciding plot works for every game: the mechanics of a game will often give the participants the impression that certain questions are open, and if believing those questions are open conflicts with a pre-planned sequence of events then something has to give (in so-called traditional play it’s often the game mechanics that give – the GM will start fudging in order to achieve the planned plot). Most traditional RPGs give the players the impression that they’ll have the freedom to choose where to go and what to do, which is frequently incompatible with a crafted plotline. This explains why some people find it much easier to achieve functional play with these games when they use a sandbox approach rather than a plotline approach to play.

In a well-designed game the psychological incentives aren’t operating at cross purposes, so what you do or don’t prep is an important element of game design, and should rarely be a casual decision made at the whim of one participant.