Pre-defined Battery¶

The Pre-defined usage type runs tasks in a fixed, predetermined order. Once a participant starts, they move through each task in sequence without any choice or branching. This is the most common mode for standard research studies and clinical assessments.

How it works¶

When the Central Executive receives UsageType=Predefined, it looks up the battery by its index value, builds the task list in the order defined in Batteries.js, and launches each task automatically after the previous one completes.

The participant never sees a task selection screen — they simply move from one task to the next.

Battery configuration¶

Batteries are defined in Batteries/Batteries.js. Each battery is built in two steps: first you define the task list, then you register the battery.

// Step 1: Build the task list
var List = []

List.push({
  Task: "Word Recognition",        // Name of the JATOS component
  Parameters: "WordRecog_Spoken",  // Parameter set from the task's config file
  Instructions: "Default",         // Instruction set to display
  IconName: "Word Recog",          // Short label for User Choice icon grid
});

List.push({
  Task: "Matrix Questionnaire",
  Parameters: "GAS_001",
  Instructions: "Default",
  IconName: "GAS",
});

// Step 2: Register the battery
BatteryList.push({
  index: 123,                                   // Unique integer, used in the URL
  name: 'Neural Cognitive Mapping Lab',         // Study name shown in the header
  description: '',                              // Optional description
  TaskList: List,                               // The task list you built above
  BatteryInstructions: "Neural Cognitive Mapping Lab",  // Battery-level instruction key
  HeaderButtonsToShow: ['Home', 'Quit', 'Stop'],        // Buttons shown on every task page
  Redirect: 'www.uottawa.ca'                   // URL to redirect to on completion
});

Task list fields¶

Field	Type	Description
`Task`	String	The exact name of the JATOS component that implements this task. Must match the component name in JATOS precisely (case-sensitive).
`Parameters`	String	The parameter set name to load from the task's configuration file (`config/<TaskName>.js`). Different parameter sets run the same task with different stimuli, timing, or settings.
`Instructions`	String	Which instruction set to use. `"Default"` loads the standard instructions for this task and language. Custom instruction variants can be created and referenced by name.
`IconName`	String	Short label displayed on the task button when the battery is run in User Choice mode. Has no effect in Pre-defined mode but should still be set.

Battery-level fields¶

Field	Type	Description
`index`	Integer	Unique identifier for this battery. This is the value passed in the `Battery=` URL parameter. No two batteries in `Batteries.js` should share an index.
`name`	String	Human-readable study name shown in the page header during tasks.
`description`	String	Optional free-text description. Can be an empty string.
`TaskList`	Array	The ordered array of task objects built above. Tasks run in the order they appear in this array.
`BatteryInstructions`	String	Key for battery-level instructions shown before the first task (if configured).
`HeaderButtonsToShow`	Array	Which header buttons to display on every task page. See Header Buttons for all available options.
`Redirect`	String	URL (without protocol) to redirect participants to when the battery is complete. The platform prepends `https://` automatically.

Selecting a battery via URL¶

The Battery URL parameter specifies which entry in BatteryList to load by its index value.

https://your-server.ca/publix/STUDY_CODE?UsageType=Predefined&Battery=123

UsageType=Predefined tells the Central Executive to run tasks in sequence.
Battery=123 loads the battery with index: 123.

Change Battery=123 to any other index value to run a different battery with the same study link format.

Task ordering¶

Tasks run in the order they appear in the TaskList array — top to bottom, exactly as written. To change the order, reorder the List.push() calls in Batteries.js.

Reusing tasks

The same task component can appear multiple times in one battery with different Parameters values. For example, you might run Word Recall with a short word list early in the session and with a long word list later.

What the participant sees¶

In Pre-defined mode, participants experience a seamless sequence:

The first task loads with its welcome and instruction screens (if enabled in the task config).
After completing the task, scoring runs silently in the background and data is submitted to JATOS.
The next task loads immediately.
This continues until all tasks are done.
The participant is shown a thank-you message and redirected to the Redirect URL.

The participant has no visibility into what tasks are coming or how many remain.