ComLabGamesUser Guide version 2026-11-13T12:55Z
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Game Types And What You Can Explore

Start with the decision you want participants to face: do they choose actions at the same time, react to earlier decisions, bid for one item, trade repeatedly, or move through a process of your own design? The game type supplies the structure of the experiment. Your rules, information, incentives, and presentation determine its content.

This chapter explains what each type can achieve. The linked Design chapters explain how to build it. Examples below describe possible experiments; they are not all ready-made definitions in the catalog.

Choose A Game Type

Several types may represent the same substantive problem. Choose the structure that makes the important decisions clearest, then check whether it provides the information and timing your experiment needs.

Strategic Games: Simultaneous Choices In A Matrix

A strategic game connects a combination of participants' actions to an outcome and a payoff for each recipient. Each decision dimension has a finite list of actions. A familiar two-player example has one player's actions in rows and the other's in columns; the definition can contain additional dimensions.

Participants make their current choices without seeing the others' current choices. They may know the rules, possible payoffs, or earlier outcomes according to the authored presentation. The current Strategic runtime executes concurrent decisions; use a Tree when the order of moves matters.

Suitable questions. Does a change in incentives encourage cooperation? Can participants coordinate on the same outcome? How do individual and joint interests differ? Do choices change when a game is repeated?

Example. Two participants choose Cooperate or Compete. Changing one outcome's payoffs lets you compare how incentives affect their choices. The built-in Cooperate or compete? game provides a small starting point.

What you define. The actors, actions, payoff recipients, and payoff formulas for each action combination. Optional Nature adds a random outcome dimension. Assignment and presentation define roles, repetitions, and the information participants receive.

What to examine afterwards. Action and outcome frequencies, individual and joint payoffs, and changes across rounds or groups. A large number of actions or dimensions creates many outcome cells to specify and check. If participants should enter an amount rather than select a listed action, consider FFG.

Build a Strategic game · Try the introductory examples

Extensive Games: Decisions And Information In A Tree

An extensive game represents a sequence of decisions. A Player node identifies who acts, branches are the available actions, Nature nodes introduce chance, and terminal Payoff nodes specify the outcome. The path taken through the tree determines which later decisions become relevant.

Information sets let you connect compatible decision nodes when the participant must not distinguish which of those nodes has been reached. This makes the information available at a decision part of the game, alongside the order of moves.

Suitable questions. Does someone accept an offer after seeing it? Is a threatened response actually chosen when its decision is reached? How does an earlier decision change another person's behavior? What changes when information is concealed or an outcome is uncertain?

Example. One participant offers a division of a resource and the other accepts or rejects it. Terminal payoffs specify the consequences. The built-in Offer and acceptance game demonstrates this structure.

What you define. Who acts at each decision, the available branches, chance outcomes, information sets where needed, and payoff formulas at the ends of paths. Node descriptions can explain the decision in the context of the experiment.

What to examine afterwards. Which paths and terminal outcomes occurred, choices at particular decisions, and resulting payoffs. A decision not reached is different from a participant choosing not to act. As the number of branches grows, so does the tree; repeated numeric decisions and ongoing resource updates are often easier to express in FFG.

Build an Extensive game · Try the introductory examples

Auctions: Competition For An Item Or A Contract

An Auction game gives participants a defined bidding mechanism and settlement rule. In buying, participants compete for an item; a winner's profit is value minus payment. In procurement, participants compete to supply an item or service; a winner's profit is payment minus cost. Non-winners receive zero under the standard auction rules.

Information and direction are separate choices. With private information, participants have their own values or costs. With common information, the true value or cost is shared, while each participant observes a noisy signal. That signal informs bidding; the true common value or cost determines the winner's profit.

Suitable questions. How do bids compare with values or costs? How do first-price and second-price rules affect bidding? Does imperfect information lead to over-optimistic winning bids? How do the observed prices differ between mechanisms?

What the mechanisms do.

Example. Give three participants private values and run a sealed-bid first-price auction. Compare the winning bid, value, payment, and profit. Buy one item is the introductory example. A definition can contain one or two Auctions, with an optional Stage between them; differences in information and eligibility should be considered when comparing their outcomes.

What you define. Mechanism, buying or procurement, private or common information, distributions and signal noise, settlement, relevant timing/prices, eligibility, and participant explanations. Auction Layout is a settings workspace; the participant board presents the bidding task separately.

What to examine afterwards. Submitted or accepted bids, winner, clearing price, profit, and whether a sale occurred. This type models the supported auction mechanisms. For repeated exchange among buyers and sellers, choose Market; for a custom allocation protocol outside those mechanisms, assess whether FFG can express its rules.

Build an Auction · Auction rules and settings

Markets: Trading And Changing Holdings Over Time

A Market game lets participants trade one or more assets through buy and sell orders. Each participant starts with cash and holdings, and the definition controls trading permissions and valuations. Trades change accounts while the session progresses; prices emerge from executed transactions.

Participants can examine the permitted market information, manage their orders, and make further decisions. The definition controls what is visible and which order actions are available. Periodic updates and transaction calculations can extend the experiment, for example with authored dividend rules.

Suitable questions. How do transaction prices relate to participants' valuations? How does the initial distribution of cash and assets affect exchange? What happens when buying or selling permissions differ? How do periodic payments affect trading and final portfolios?

Example. Give one participant cash and another a share, then let them submit matching orders. Trade one share provides a small example in which cash and holdings can be checked by hand. Larger definitions can include several assets and Player Types.

What you define. Assets, initial cash and holdings, private valuations, account permissions and limits, valuation formulas, trading duration or completion conditions, and any transaction or periodic outputs. Instructions should explain what each displayed value means.

What to examine afterwards. Orders, executed trades, prices, volume, cash, holdings, payments, and final results. A private valuation, last transaction price, and portfolio value answer different questions. Explicitly choose whether holdings are valued using private values, last-trade prices, or another supported formula. Last-trade market value is zero before an asset's first trade, so this can materially affect Results.

A Market suits ongoing exchange. An Auction suits the allocation of an item or contract through a particular bidding mechanism.

Build a Market · Valuation and other Market settings

Free Form Games: Author Your Own Decision Process

A Free Form Game (FFG) combines Stages, participant Pages, Choices, calculations, and routes. You define the process rather than fill in a matrix, tree, or standard trading mechanism. Pages communicate the situation and collect inputs; Variables retain the state required by the rules.

A Stage can collect responses from the intended participants, update values, and continue according to conditions or weighted routes. Pages can differ by audience, and activity conditions determine who is required to act. Time limits can follow an explicitly defined automatic-response path. A timeout does not by itself mean zero points; the definition must specify the resulting value and score.

Suitable questions. How much do participants contribute to a shared fund? How do they use a resource that changes across rounds? Does feedback or punishment influence later decisions? How do participants behave when decisions have several phases and their consequences depend on accumulated state?

Example. Participants enter contributions, the game calculates individual and group outcomes, and another round follows. Contribute to a shared fund demonstrates two rounds and accumulated profit. A shared-lake experiment can additionally carry a resource stock forward and update it from effort, catch, and renewal formulas.

What you define. Stages and their completion rules, who sees each Page and who acts, permitted Choice inputs, Variables and update formulas, routes, and feedback/Results. When a value must persist across rounds, its initialization and later updates must reflect that intention.

What to examine afterwards. Choices, state changes, individual and group results, and the sequence and timing of Stages. FFG has no standard payoff matrix or automatic universal profit rule: the definition's Variables and calculations establish what counts as a result.

This flexibility requires more explicit rules. FFG is built from the application's supported Pages, Choices, formulas, and process controls; it is not an unrestricted programming environment. When the supported Auction or Market mechanism already matches the experiment, that type provides its bidding or trading behavior directly. When a finite branching sequence is the main subject, a Tree may communicate it more clearly.

Build a Free Form game · Stage behavior and settings

From An Idea To A Testable Experiment

Before editing, write down who acts, what each person knows, the available decisions, how the game advances, and how outcomes are calculated. Distinguish the rules participants should understand from explanations you will reveal only during discussion.

Start with a small example, make your own copy, and change one rule at a time. Run through both an ordinary path and an alternative outcome, then check the actual values in Results and the Run Log. For comparisons, keep track of changes in information, incentives, timing, and participant assignment as well as the game type.

Quick Start · Test a game before class · Review and analyze a Run