Matan Mazor suggested to use a cryptographic hash as a seed to randomize stimulus sequences in order to prove that the preregistration happened before data collection. I thought this is a good idea. You can easily do it with JATOS. Here is how.

There is a really easy way to embed Google Slides in your JATOS component’s HTML file. I thought that this might be a quick way to write the instructions for an experiment. They aren’t the most beautiful way to present instructions (the Google Slides frame is always visible) but it’s quick, easy, versatile, and allows your participants to move forwards and backwards on the series of instructions slides.

I set up a JATOS server where everyone can try out and test JATOS: https://cortex.jatos.org.

A JATOS user told me about Cloud9 and I thought I should mention it in a blog post.

I wrote a blog post about how to get a JATOS server via Dply.co and I still like this little service quite a lot. It’s super easy to set up a server and at least initially it’s for free. I did a new Dply button that this time uses JATOS’ Docker container:

Who reads descriptions? We mostly copy code examples and change them to our needs. That’s why I added many code examples in the jatos.js reference. I hope it helps!

Since JATOS doesn’t limit what actually runs in the browser during your studies you can use all kinds of JavaScript libraries and frameworks with it. This is not possible if you use e.g. Qualtrics. One of those libraries is p5.js. p5.js lets you do otherwise complicated 2D or 3D graphics in an easy way. Have a look at the examples on the p5.js webpage to get an idea of what is possible.

Doing user input forms, e.g. for questionaires or surveys in the browser yourself often means handling a lot of <input>, <textarea>, CSS etc. Those can be quite cumbersome. One wants to concentrate on the actual survey and does not want to count radiobuttons or the pixels of the border of input fields. Therefore usually one uses a library that helps with this process. So far there where mostly jQuery UI and Bootstrap. Alpaca also does the job but I found it a bit difficult to use (although I only tried for one afternoon). Now there is a new option: SurveyJS (or survey.js - both spellings seem to be used).

Since JATOS 3.1.6 it is possible to start JATOS as a systemd service. This is probably most useful for server installations. Everything one need to know is in the documentation.

We noticed that can be difficult for people who have never heard of JATOS to understand what JATOS actually is and what it can do for them. So we started with a little series of introduction videos. We planned 3 parts so far. First one is youtu.be/H1tR8gPt6bA. I hope you like it (I’m a programmer and not an entertainer - so please be gentle with me).

JATOS 3 stores its user session in a local cache and initially I gave this cache without much thinking 256 MB of memory. 256 MB is ridiculously high for a cache that just stores a couple of user sessions. But hey I have 16 GB on my laptop - who cares. Actually people do care. Especially those who want to run JATOS on systems with limited resources like an AWS EC2 micro instance with just 1 GB. If you just have 1 GB then 256 MB is a lot.

JATOS 3 is out and it got some nice security improvements that I want to talk about in more detail in this post.

It’s probably confusing for someone who starts with JATOS to grasp the differences between the JATOS worker types. So I made an overview table of them. It’s in the JATOS documentation: www.jatos.org/Worker-Types.html#overview.

Recently I was asked to help with a broken JATOS instance. The logs were full of error messages like

I was always looking for an easy way to install JATOS on a server (to make it accessible from the Internet); but I never found an easy enough solution. Most server or cloud providers target bigger companies and have a quite complex setup - nothing one wants to do if it’s just about trying a little tool like JATOS. But lately I stumbled over Dply. It’s still in beta but it might fill this empty spot in the cloud vendor landscape.