Common session parameters

These parameters are handled by each task's launch wrapper. Support varies slightly by task — the matrix below is derived from the wrapper source code.

Parameter	Type	Default	Description
token	string	—	Authentication token for results submission. When absent (along with callback_url), the assessment runs in debug mode and displays results on-screen instead of submitting them.
callback_url	string	—	URL to POST results to when the assessment ends.
pid	string	—	Optional participant identifier. Echoed verbatim into the results: top-level pid next to token in the callback POST, inside data, and in the embed-mode postMessage. Useful when the callback endpoint does not mint per-participant tokens, or to link multi-session designs (e.g. FNAME-Pairs learning vs. delayed) from the URL alone.
show_end_screen	string	true	Set to false or 0 to suppress the green "Assessment Complete" screen after results are submitted. A Telegram WebView closes immediately instead of showing the confirmation.
tutorial	string	true	Set to false or 0 to skip the tutorial screens (alias for the show_tutorial assessment parameter).
webcam	string	—	Set to 1 or true to enable optional camera recording. Participants see a consent prompt; if they accept, the front camera records and the video is saved locally to their device at session end.
webgazer	string	—	Set to 1 or true to enable browser-based eye tracking via WebGazer.js. Participants see a consent prompt, then a 5-point gaze calibration. Gaze coordinates are recorded throughout the task and exported as a CSV file at session end. Can be combined with webcam=1.
light	string	—	Set to 1 or true to enable ambient light sensing (where the browser supports the AmbientLightSensor API). Participants see a consent prompt; lux readings are recorded during the task and exported at session end.
embed	string	—	Set to 1 for embedded mode (e.g. an ESMira PWA iframe): on completion, results are posted to the parent window via postMessage instead of an HTTP callback.
list	number	1	Which of the 4 pre-constructed balanced lists to use (1–4). Maps to the list_id assessment parameter; must match across a participant's sessions.
images	string	—	Set to 1 or true to show an item photograph above each item during the tutorial example and the learning phase (Prices). The recognition phase stays word-only. If photographs cannot be loaded, the task falls back to word-only mode.
recognition_feedback	string	—	Set to 1 or true to color the chosen recognition button green/red by accuracy (Prices). By default the selection is highlighted in a neutral color, giving no accuracy feedback.
stimuli_base_url	string	task-specific	Base URL for stimulus photographs. Images are not redistributed in this repository; point this at your private stimulus host. Defaults and hosting notes are on each task page (Prices, FNAME-Pairs).
face_source	string	bundled	Set to api to fetch random faces from the 100k-faces API instead of using the bundled curated face set.
number_of_faces_to_prefetch	number	—	How many face images to prefetch before the task starts (only relevant with face_source=api).

Support matrix

Parameter	PVT-BA	SART2	Prices	FNAME	FNAME-Pairs	mVLT	Visual Search	Symbol Search	Color Dots	Grid Memory	Color Shapes
token	✅	✅	✅	✅	✅	✅	✅	✅	✅	✅	✅
callback_url	✅	✅	✅	✅	✅	✅	✅	✅	✅	✅	✅
pid	✅	✅	✅	✅	✅	✅	✅	✅	✅	✅	✅
show_end_screen	✅	✅	✅	✅	✅	✅	✅	—	—	—	—
tutorial	✅	✅	✅	—	✅	✅	✅	—	—	—	—
webcam	✅	✅	✅	✅	✅	✅	✅	✅	—	—	✅
webgazer	✅	✅	✅	✅	✅	✅	✅	✅	—	—	✅
light	✅	✅	✅	—	✅	—	✅	—	—	—	—
embed	✅	✅	✅	—	✅	—	✅	—	—	—	—
list	—	—	—	—	✅	—	—	—	—	—	—
images	—	—	✅	—	—	—	—	—	—	—	—
recognition_feedback	—	—	✅	—	—	—	—	—	—	—	—
stimuli_base_url	—	—	✅	—	✅	—	—	—	—	—	—
face_source	—	—	—	✅	—	—	—	—	—	—	—
number_of_faces_to_prefetch	—	—	—	✅	—	—	—	—	—	—	—

✅ = the launch wrapper reads this parameter. For m2c2kit library tasks, unknown query parameters are forwarded to the game engine, so only the parameters listed here and on the task pages have an effect.