Whenever I upload a task to JATOS for the first time, via the OSWeb and JATOS control panel I always get the message:

Interestingly, the task is actually uploaded to JATOS without issue, and on subsequent saves (with the same UUID), the message does not appear.

I'm running:

Opensesame 4.1.6

JATOS v3.10.4

My colleagues have the exact same issue. While it's not a critical issue, as the task it actually uploaded despite the error message, it does lead to confusion and questions from our researchers.

Kind regards,

Kerwin

Hi, I am running a visual world eye tracking experiment using OpenSesame 4.1.9 and OSWeb 2.2.9 on MindProbe. The camera opens correctly during the experiment but WebGazer never produces any gaze predictions and my gaze_json variable is always empty.

The browser console shows these errors:

• Failed to load resource: face_mesh_solution_simd_wasm_bin.js (404)
• Failed to load resource: face_mesh_solution_p...assets_loader.js (404)
• Failed to load resource: mediapipe/face_mesh/face_mesh.binaryb (404)
• No stream
• Uncaught TypeError: t is not a function (face_mesh.js:53)

I am attaching a screenshot of the console. It looks like the TFFacemesh model files are missing from MindProbe's server. Is this a known issue and how can I fix it?

Thank you

I'm experiencing a complete outage on jatos.mindprobe.eu where **all** my OSWeb studies — including previously deployed and confirmed-working ones — fail on the "Building screen" stage. This appears to be a recent server-side regression in the OSWeb runtime.

### The error

Browser console output:

  PixiJS 5.3.12 - WebGL 2

  text.es.js:1307 Canvas2D: Multiple readback operations using getImageData are faster...

  transfer.js:121 file pool embedded in HTML (N files)

  transfer.js:246 All audio files have been loaded and decoded

  screen.js:202  Uncaught (in promise) TypeError: Cannot read properties of null (reading 'length')

            at Screen._setupClickScreen (screen.js:202)

            at Parameters._initialize (parameters.js:24)

            at Runner._setupContext  (runner.js:143)

Tracing the call chain: `this._runner._welcomeText` is `null` when passed to `_setupClickScreen`. The `typeof text === "undefined"` guard at the top of the function does not catch `null` (because `typeof null === "object"`), so the function continues and crashes when reading `.length` on the null text.

### Evidence this is server-side, not study content

1. **Previously-working deployed studies** that ran fine for weeks now produce the same error without any changes from my side.

2. **A reference .osexp** I successfully ran earlier this year now fails identically when re-uploaded.

3. **Multiple .osexp variants** with different headers (with/without `set background`, with/without `set jatos_uuid`, Python `True/False` vs legacy `yes/no` booleans, ASCII vs Turkish titles, with/without inline_javascript blocks, with/without `run_if` conditions) all produce the identical error.

4. Tested across **two Mindprobe accounts** and multiple browsers (Chrome, Firefox, incognito).

### Suspected cause

This looks like a recent OSWeb runtime update or transpilation pipeline change on the Mindprobe server. The failure pattern (identical error on unchanged previously-working studies) is hard to explain otherwise.

Thanks,

Büşra

Description of the issue:

I am running an online experiment using OSWeb with JATOS as the backend. The experiment runs correctly from start to finish in all cases, but intermittently (roughly 1 in 5 sessions) no trial data is logged at all. When this happens, the JATOS result file contains only a single opening square bracket [ with no data records inside it. The JATOS server is hosted at a university server (jatos1.psy.vu.nl)

What I observe:

• The experiment loads and runs completely normally from the participant's perspective
• All trials are displayed and responses are recorded visually
• At the end of the experiment the screen gets stuck at the data transfer stage
• In the JATOS result viewer the result entry exists but contains only [
• When it works correctly, data is logged incrementally trial by trial as expected

What I have tried:

1. Originally used the built-in OpenSesame logger item — same intermittent failure
2. Replaced the logger with explicit jatos.appendResultData() calls in an inline_javascript item inside the trial loop — same intermittent failure persists
3. The jatos.studyResultId is set correctly at the start of the experiment — so the session initialises properly

Questions:

1. What does the [ in the result file indicate — is this OSWeb opening the result array before any data is written?
2. Is there a known issue with jatos.appendResultData() in OSWeb v2.2.9 when called repeatedly inside a trial loop?
3. Is there a recommended way to verify within OSWeb whether appendResultData() succeeded?
4. Is there a more robust way to log trial-level data in OSWeb that does not rely on appendResultData() inside a loop?

Any help would be greatly appreciated. This is part of a mobile EEG validation study and reliable data logging is critical.

I am working on an event segmentation experiment in OpenSesame (running online via JATOS/Prolific) and I have two questions.

Question 1: Tracking spacebar presses during video playback

I want participants to press the spacebar whenever they perceive an event boundary while watching a video. I need to collect all spacebar presses during the video (not just one), log the timestamp of each press in milliseconds relative to the video start, and have these saved in the logfile per trial. I currently have an inline JavaScript item playing the video. What is the best way to collect and log these keypresses in OSWeb with accurate millisecond timing aligned to the video?

Question 2: Attention check after every 3rd video not working

I have an attention check inside my trial sequence that is meant to verify whether participants have actually watched the video. It consists of a sketchpad (showing a question about the video) and a text input where participants have to write their answer. I want this attention check to appear after every 3rd video. I am using a video_count variable that increments by 1 after each video ends, and I set the run-if condition on both items to:

video_count % 3 == 0 and video_count > 0

However the attention items never appear at all. I am currently using a sketchpad for the question display but I am not sure if that is the right item type for this. Is there something specific about how run-if conditions work in OSWeb that I am missing, and is there a better way to trigger an attention check with a text input field every N trials in OSWeb?

Thanks in advance.

I want to have an input text and give the user feedback bu showing a green or red circle on a sketchpad, depending if the answer was correct. Nut I saw my input text variable is not recgnised in the inline javascript, onlty in logger, so how can I give the user that feedback?

I have an input text which is in a loop.

In the first time it shows the cursor is on the input field and it's ok,

but after showing a sketchpad in the 2nd iteration of the loop, the cuursor is not showing in the item, and I need to click the mouse, in the item, tried autofocus, but it does not work

1. It asks the participant to fill in a subject number, which should not happen.
2. It does not redirect the participant to Qualtrics.

The problems do not occur in Firefox or Safari. I am up-to-date with the most recent versions of Chrome and OS Web. Below are screenshots of the request for a subject number, and what happens at the end of the experiment when it does not redirect to Qualtrics. Attached is the experiment file. Would welcome any suggestions for making the experiment run on Chrome!

Try to change color of rectanglem

wrote in inline java script , with chatgpt help:

// choose rectangle color randomly

// blue = "#0000FF", green = "#00FF00"

var colors = ["#0000FF", "#00FF00"];

vars.rect_color = colors[Math.floor(Math.random() * colors.length)];

and in the sketchpad I drew a recyangle and wrote in the color - color=[rect_color] or color="[rect_color]",

but either I get the variable is not recognised or nothing is shown

We are currently using a Mindprobe JATOS server to run an OSWeb experiement. We have recieved several completed runs which seem to work, however some participants get the error message "A problem occurred: Failed to transfer data" when finishing the study. In the console we get the error "403, study run is already finished (study result######)".

We have in the code included some special character: ø and å, and after finding the following discussion are wondering if that might be the problem? https://forum.cogsci.nl/discussion/7049/another-a-problem-occurred-failed-to-transfer-data

We have tried different browsers, but the results are a bit confusing.

It works in:

• Microsoft edge (Windows)
• Google Chrome (Windows)
• Safari (Mac)

It doesn't work in:

• Mozilla Firefox (Linux and Windows)
• Google Chrome (Mac)

We hope you can help!

Thanks in advance!

Best regards,

Confused Wug and Puzzled Wug

I am designing a simple number comparison task in which a child sees two numbers and needs to select the bigger number. We are planning to collect data using iPads by uploading our study to JATOS. I designed the task using a sketchpad and mouse response (so a child can click the number). My problem is that I am using the variable 'cursor_roi' to keep track of children's responses and whether or not they got the answer correct. However, I noticed that my inline script using cursor_roi does not work on JATOS/OSWeb. Is there a way to fix this/different way to keep track of children's responses and create a 'correct' variable that shows whether or not they got the problem correct?

Thank you all for your help!

I want to use mouse responses to collect reactions in a a flanker task (i.e. categorize central letter as consonant or vowel) which should be clicked and it looks fine in the programming (see below).

However, when I run it in Google Chrome, something odd happens (i.e. screen using different coordinates)

I attached the code (sorry for not translating the intro and informed consent) - any suggestions are welcome.

I also worked with the java script roi definition which solved the problem partially but did not yield the expected coordinated in the result file and the experiment does not advance as expected (which it does when using the cursor_roi in the code added)

I am reaching out ask for help from anyone who has experience/knowledge of recording participant audio in a browser-based experiment. I am new to online experiments and therefore to javascript and would love any guidance on the (additional) steps I'd need to take in order to record participants' vocal responses. Any helpful links, guidelines, or sample codes are highly appreciated!

I'm trying to run another osweb experiment. Although the experiment runs perfectly with psychopy, when reverting to osweb it does not run.

There seem to be missing files.

The experiment freezes when an audio file is supposed to be played, and when debugging, a message like this always appears:

tmp3_7avyab.html:1 Uncaught (in promise) "pract3.ogg" does not exist in the file pool

The audio files are correctly coded to ogg to reduce the file size. I opened one audio file with my browser, and it played.

I tried to both add the sound files through the add button and by dragging them to the file pool. The same message appears either way.

I've downloaded the latest version of OS.

My previous experiment does not run in my browser any more.

I have a Win10 PC, and use either chrome or firefox.

Any ideas?

Thank you,

Fotis A. Fotiadis

I'd like to design an original SART task. In this task, numbers 1-9 are presented. Each number remains on the screen for 250 ms. Then, a mask screen appears for 900 ms. The subject can react either on the number or the mask screen, but even if they do, they must not move on to the second number until the total time (1150 ms) has elapsed. I tried to do this using a coroutine, but this time, the response times were not recorded. Can you help?

Not sure whether to post here or on the JATOS forum.

We're trying out the JATOS 3.9.6 version (from 3.9.5).

For our 3.9.5 version the OSWeb "Open from JATOS" functionality works fine for our self-hosted server.

For our 3.9.6 server it throws an error:

First I figured maybe something was not set up properly with the API keys on the test server, but if I run the curl API test command it comes back without issue.

Using curl to get export a specific study also works fine.

EDIT: I also just tried it on the cortex server, and getting the same error. Again, running curls (e.g. from the Swagger UI page) seem to work fine, and will give me the overview of all available studies.

Any idea what may be going wrong?

Thanks!

Kerwin

I am trying to make a visual world paradigm, but since I do not have an eye-tracker, I planned to use WebGazer.js as an external library. That is why I attempted to join the example experiments for the two (the VWP example and the calibration script), which I found among the documentation on the website. However, I have come to a problem with OSWeb not supporting coroutines, which seem to be necessary for VWP to work properly. I have found an old comment on a workaround for this using inline_scripts and Java, but as it is quite old, and made for a completely different experiment, I am not sure how to implement it.

If somebody could help me, I would appreciate it very much, as I feel completely lost!

P. S. I have the newest version of OpenSesame installed.

I want to implement a Likert Scale, associated to a bunch of pictures, using OSWeb.

I found some instructions here on the forum about rating scales, but they all refer to inline_script, which I cannot use due to OSWeb. I can only use inline_javascript and inline_html.

Also, I'd like the likert scale to show up below a picture. The pictures that need to be evaluated are about 100, and I'd like them to show up in a randomised order. I already uploaded them all in the pool.

I tried to create a loop with 3 column, of which the first one ("image") is filled with the images' names, and to add an inline_html after, which "recalls" the picture from the loop. But i can't make it work.

Do you have any suggestions?

I am trying to rotate a visual stimulus in an experiment.

For the local version, it works totally fine. However for the online version, there is a clear offset from the center (this offset changes for each rotation). I tried to fix it through using a java inlinescript and manually setting x and y to 0 (and using center = 1). This also did not solve my problem (I ensured that width and height are equal).

So I was wondering if there is any possibility to "anchor" the stimulus in the sketchpad such that it is only rotated around the anchor point (without hardcoding x & y for each trial seperately).

Thanks in advance!

Best

Carla

I tried to use a csv file as input for a loop in an OSWeb experiment. My experiment works for the PsychoPy backend but not for the OSWeb backend.

I have tried using different types of csv files and also chatted with SigmundAI but unfortunately I have not found a solution.

I have attached the experiment-file I used to try to find the error, the last version of the csv-file and a screenshot showing the error message. Could you please help me resolving this error message?

Thanks in advance!

Best

Carla

I have an experiment where participants listen to a word and then respond by pressing a key. I have more than 1000 trials. Everything works fine in Firefox but in Google Chrome some words fail to play. I get the following error when running in Chrome: [Intervention] Blocked attempt to create a WebMediaPlayer as there are too many WebMediaPlayers already in existence

I'm really not experienced this so if anybody has any ideas on what I could try to get the experiment to work consistently in Chrome, I'd appreciate it!

What can cause the page to reload like this?

I've added the experiment file (edit: I'm unable to do that here). It runs fine the first trial up to "askRecogQuestion" (I can even see it displaying the result of that function very very briefly before "redirecting").

I have an experiment that should be run online using OSWEB. One of the variables was called "Object", referring to the name of an object image shown in the task. The experiment used to run without issues some years ago, but now this caused an application / script error in running the first item in the sequence from the loop table in which the Object is defined:

The issue was resolved by changing "Object" to "ObjectName" in the loop table.

We have a student running an experiment online who has deactivated the study via JATOS (removing the check box for "osweb component"). Is there an option to display a custom message informing the participant that the study has finished?

I have a problem with my experiment in OpenSesame in OSWeb. I have several sketchpads in a loop. Sentences from the loop table are displayed on these sketchpads. For example, a column in the table is named 'word_2' and on the sketchpad I have the text '{word_2}' to display the text from the column. When I run the experiment in the browser, I encounter the problem that some letters are cut off. Specifically uppercase umlauts like 'Ä' and 'Ü' are missing their dots. I thought it was a problem of displaying unconventional letters, but if I make the font size really really small, the dots show up, which indicates that they are cut off. Is there a way to fix this?

Thank you in advance,

Sophie

I am currently trying to set up a self-paced reading study using OpenSesame. I have some welcome screens, then the trial sequence, and then some demographic questions followed by a goodbye screen. The first problem is that this goodbye screen will not go away. I have currently set the duration of the goodbye screen (sketchpad) to 'keypress' but no matter what key I press, it will not go away and so the experiment cannot end properly. I have also tried to set the duration to 3000ms but it will also not go away after that time. This problem only occurs when I set the experiment to OSWeb backend. In the PsychoPy backend, I did not have this problem.

The other problem I have is that it seems like the logger is not saving the answers to the demographic questions at the end to the results file.

Can anybody help me with these problems?

I have attached the experiment file to this post.

Thank you in advance!

I'm doing an experiment with OpenSesame and I'll upload it to mindprobe.

As far as I know, I can't use forms with OSWeb, so I used inline_html to ask for Age and other variables.

I attach the script to ask for age. Before this inline_html, I included an inline_javascript to start the variable age (vars.age = ' '). Then, in the logger, I could include this variable.

When I did the experiment, the script worked and I could enter "age". However, when I got the results, the column age is empty.

I don't know what the problem is. I hope you can help. Thank you.

Best,

Teresa

The sample already hosted on https://jatos.mindprobe.eu/publix/BowSAFY2VWl seems to work fine so I downloaded the actual experimental file from here https://osdoc.cogsci.nl/3.3/attachments/webgazer.osexp

and added the link to the Webgazer library as shown in the instructions

and set the experiment to run in the browser using OSWeb

However, when I run it I end up getting an error that seems to indicate that the Webgazer library isnt actually being loaded:

So am I just missing some step in the setup, or is this a bug?

Also, I noticed that the addition of the link to the Webgazer library and the setting for running the experiment in the browser dont actually get saved from session to session when I save the experimental file, and need to be set every time I start OpenSesame.

Thanks in advance for any help!

I'm designing an online experiment in which participants are tasked to navigate a grid world and collect resources.

For this purpose I'm redrawing a canvas() object on each iteration (whenever the participant makes a move).

In principle everything functions as it should, but over the course of ~2000 iterations, my experiment accumulates ~1700mb of memory, most of which seems related to rendering / drawing (see screenshot of heap snapshot).

I've tried separating out a static and dynamic canvas, but this doesn't work because (unless I'm missing something) I cannot layer canvases. I also tried changing parts of the canvas as is possible in python, but unless I did it wrong this doesn't seem supported in javascript.

My question is: given that I'm constantly redrawing my canvas and everything in it, is the accumulation of memory to be expected, or is this indicative of something going (or me doing) something wrong? If the latter, would you have any recommendations for improvement?

Many thanks!