From Lioness wiki
Jump to: navigation, search

The parameters of your LIONESS experiment are set in this menu. Your settings are stored in the globals table. In each participant screen, the parameters defined here are available through JavaScript. The variable names are exactly as described here.

The menu contains three tabs: predefined parameters, messages and own parameters.

Predefined parameters

Parameter table.png


This parameter regulates whether the experiment is active, and is set in the Control panel. When the experiment is 'active', the value of this parameter is 1, otherwise it is 0. Participants can only enter active experiments.


This parameter regulates the test mode, and is set in the Control panel. In the test mode, multiple participants can be operated from the same browser, using different tabs. This is useful when developing your LIONESS experiment.


This parameter sets a 'cap' on the total number of participants allowed to enter an experimental setting. In test mode the cap is removed. When a participant tries to enter a session after this number has been reached, they will be redirected to a screen displaying a message indicating that the current session is full.


This parameter defines the size of the groups. Once the number of participants waiting in the lobby equals this number, the controller algorithm will match them into a group and pushes them to the next stage. Typically, this next stage will be the first stage of a period (see loopStart).


This parameter defines the total number of periods in the experiment. Periods start with the stage defined in loopStart and end with #loopEnd).


The parameter defines which stage is the first stage of a period. When a group reaches the stage define in loopEnd, all participants in that group will be directed here, if the period number has not reached the value set in #numberPeriods.


This parameter defines which stage is the last stage of a period. When a group reaches this stage, the period number of this group will be increased with 1, and all members will be redirected to the stage defined in #loopStart. When the period number has reached #numberPeriods, the group will proceed to the stage defined right next to this stage. Note that in the last stage of a period, participants will typically have to wait for all of their group mates to finish the period, that is, they have to 'wait for all' before they can proceed.


This parameter sets the guaranteed participation fee, which participants will receive independently of their performance in the experiment.


The exchange rate can be used to convert experimental points into real money.


Optionally you can open one stage in a new window. This window will not contain any navigation buttons (such as the arrows for 'previous page' and 'next page') and will block a participant from editing the address bar. By design, LIONESS experiments overwrite the navigation history so that participants cannot browse the experimental pages by using these buttons. However, this option can be useful in the stage right after an instructions page. This way, the participants can always refer back to the instructions.


This parameter defines how dropouts should be handled. Participants who dropped out (e.g. by failing to respond within the set time) will be directed to a screen displaying a message indicating that their session is over. From the menu, you can choose from three options defining how to deal with the other group members.

Terminate group

If one participant drops out, the other participants in their group will be led to a screen displaying a message indicating that one of the group mates has dropped out and that the session is over. When you choose this option, consider taking measures to compensate these group mates as they might expect to earn some more in the periods they will not be able to complete due to this dropout.

Proceed with reduced group

This is the default setting. Once a participant drops out, the other group members continue with a group reduced in size. The variable 'currentGroupSize' in the core table will be reduced with 1. When you choose this option, consider adding a warning message (using JavaScript) to the other participants. Also, keep in mind that in many cases, the data generated by groups reduced in size requires special treatment in analyses.

Disable exclusion

This option is best used for individual (non-interactive) tasks, or when you deploy LIONESS in the laboratory (that is, not with participants recruited online), where dropouts are atypical. When a participant loses connection to the server (e.g. due to network problems), you can try to solve this without the participant dropping out. The other members of the group typically wait and continue once the problem is solved.


This defines how the participants in the lobby are matched in groups. There are two options to choose from.

first come, first serve

This is the default option. As soon as the number of participants in the lobby equals #groupSize they are matched and can start interacting. This setting aims to minimize waiting time.

match groups with unique roles

In some cases you might want to allocate roles before you assign participants to groups. Before participants enter the lobby, they can be assigned a role (by setting their variable 'role' in the core table. Roles need to start with 1, and run up to value value of the groupSize. For example, if you have groups of 3, a group will be formed as soon as a set of players with roles 1, 2 and 3 can be formed.


Each experiment contains a page with messages tell participants that their session has terminated prematurely. These messages are necessary for clear communication with participants upon dropouts, and to provide information as to why they cannot proceed with the session. Each of the messages has a default text, which can be edited in the messages tab. Messages are displayed conditional upon the event that triggered the termination (see below).

Parameter table messages.png


The experiment is currently not active (see active).


A participant tries to connect to the server while they are already connected.


The maximum number of participants for this session has already been reached.


The participant is not connected to the server.


The participant has been manually removed from the session.


The participant did not make a decision within the set time. They are removed from the session.


The participant's group has been terminated due to a dropout of a fellow group mate. This is only used when the dropout handling has been set to 'terminate group'.


The participant tries to enter a session using Internet Explorer. This browser is not supported.


The participant has not successfully completed the control questions after the set number of attempts. They cannot continue.

Own parameters

Parameter table addOwn.png

You can add your own parameters by clicking the '+' sign. In the left hand side field you can give the variable a name, and in the right hand side field you can set its value. Only numerical values are supported. The parameter will be available for JavaScript in all the participant stages. You can delete your parameters by clicking the bin icon.