The Four Information Systems of Social Deduction Games
The Importance of Information
Social deduction games tend to be about information. Most players have the goal of accumulating information about the roles of the other players or preventing information about their own role from being revealed. This structure dates back to Mafia, considered by some to be the original social deduction game. In Mafia, the Town team has the goal of finding and eliminating the Mafia, while the Mafia team has the goal of staying hidden. Information is critical because the Town can win the game if they build up enough information about the roles of the other players. In the absence of such information, the Mafia will likely win.
A Simple Classification
There are multiple types of information in social deduction game design. One important distinction is whether information is complete or partial. Complete information reveals a player's role or faction with certainty, whereas partial information alters the probability that a player has a role without outright revealing the role. The other main distinction is whether information is direct or indirect. Direct information is generated by the player who gains the information, whereas indirect information is generated by the player who reveals the information. The combination of these two axes, complete vs. partial and direct vs. indirect, yields 4 different information systems.
1. Complete Direct Information
In Mafia, some formats use a Cop role. Each round, the Cop can target one player and learn whether they are on the Town team or the Mafia team. This information is complete, as it fully reveals the target player’s role. It is also direct because the Cop fully controls which player to target and personally gains the information about the target.
2. Partial Direct Information
In Mayday!Mayday!, players have a total of 3 Identity cards, all of which are hidden from the other players. A player on the Honest team will have 2 Honest cards and 1 Infiltrator card, whereas a player on the Infiltrator team will have 1 Honest card and 2 Infiltrator cards. Over the course of the game, players can look at the Identity cards held by other players, thereby obtaining direct information. Yet, this information is partial, as viewing only 1 card is insufficient to determine someone’s role with certainty.
3. Complete Indirect Information
In BANG!, each player has a role of either Sheriff, Outlaw, Deputy, or Renegade. The Outlaw team wins the game if the Sheriff is killed, whereas the other players typically want to prevent the Sheriff from dying. The role cards of the Outlaws stay hidden for the entire game, but their roles tend to be revealed anyways through their actions. Essentially, if a player attacks the Sheriff, they are almost certainly an Outlaw. This information is complete because it fully identifies the player as an Outlaw, but it is also indirect because it is generated by the player whose role is being revealed.
4. Partial Indirect Information
In The Resistance, players are on either the Resistance team or the Spy team. The game consists of up to 5 missions which can either pass or fail depending on the actions of the players involved. A mission involves multiple players, each of whom can individually choose a pass or fail action (if one player fails, the entire mission fails). Once players make their choice, the pass and fail cards are revealed in a shuffled order. The Spies win the game if three missions fail, whereas the Resistance win if three missions pass, meaning that only a Spy would choose to fail a mission. Thus, the failure of a mission means that at least one of the players on the mission is a Spy, but it is not known which player is the Spy. This information is partial, as it reveals that there is at least one Spy in a given group of players without specifically identifying which player is the Spy. The information is indirect as well because it is generated through the voluntary actions of the Spy.
Comparing Different Systems
The ideal information system is ultimately a question of personal choice. Still, I would like to make the case for partial indirect information, as I consider there to be drawbacks to both complete and direct information.
Complete vs. Partial
The nature of complete information is that it generally needs to be used sparingly in order for the game to remain balanced. In Mafia, most formats involving a Cop have only one Cop, with none of the other Town players having any sort of information role. This is necessary; the Cop is so powerful that if there were too many Cops, it would become too difficult for the Mafia to win. Yet, this design means that the other players are left in the dark. In BANG!, information about the identities of the Outlaws is available to all of the players, but this system detracts from the suspense of the game. When the role of every player is known, social deduction is no longer the focus of the game. Thus, a compelling social deduction system must ensure that any complete information in the game is limited in quantity. Conversely, with a system of partial information, every player can have access to multiple pieces of information without breaking the game.
Direct vs. Indirect
In direct information systems, the same player is responsible for both creating and acquiring any newly generated information. This differs from indirect information systems, where one player gives up information to another player. In other words, direct information is involuntarily demanded, whereas indirect information is voluntarily given up. Thus, under an indirect information system, players who wish to keep their role secret have the option of doing so. The information generation is driven by natural player actions rather than special powers which allow roles to be viewed.
It’s important to note that a game which uses indirect information must provide some sort of incentive for players to willingly give up information to their opponents. In The Resistance, a Spy can choose between passing or failing their mission, with each option having its own tradeoffs. By passing the mission, the Spy advances the win condition of their opponent but maintains trust with the other players. Conversely, by failing the mission, the Spy advances their own win condition but draws suspicion to themselves. A social deduction game which uses indirect information must be balanced carefully in order to ensure that the right amount of information is generated over the course of the game.
How I Designed Demon Summoner
Unsurprisingly, I’ve designed Demon Summoner to rely on partial indirect information. Similar to how players in The Resistance can choose to pass or fail a mission, players in Demon Summoner can choose to capture or release their demon. These actions advance the win conditions of the Righteous and Evil teams, respectively. The difference in Demon Summoner is that a player’s action is revealed individually rather than as part of a cluster of actions from multiple players. Of course, a player who releases a demon is not guaranteed to be Evil, since players may be forced to release depending on which demon they are given, and released demons are not revealed to other players. Thus, the action of capturing or releasing a demon generates partial indirect information.
Prophecies can also be used to generate information, albeit not enough information to determine any player’s role with certainty. By using a Prophecy, a player can view another player’s demon before it is captured or released. Demons are hand-picked by the Demon Summoner, who plays for the Evil team, meaning that there is strategic advantage to passing the right demons to Evil players. Yet, viewing a demon does not grant full knowledge of a player’s role. For these reasons, prophecy information is also partial and indirect.
It was not always the case that Demon Summoner primarily used partial indirect information. Early versions of the game used a secondary information system of Mastery rather than Prophecy, where players with certain Masteries could use powerful information-generating abilities. One Mastery, for example, enabled viewing the role of another player, thereby generating complete direct information. The early playtesters of Demon Summoner had concerns with the Mastery mechanic, as it generated too much information and could not be played around by the Evil team. After about a dozen initial playtests, the Mastery mechanic was replaced with Prophecy, and gameplay improved significantly.
By learning about the differences between various information systems in social deduction games, I’ve been able to make better design decisions in Demon Summoner. This knowledge was built up mostly by playing other social deduction games, and I’m grateful for games like Mafia and The Resistance for showing me what kinds of designs are possible. I look forward to seeing future innovative social deduction games across the various types of information systems.
