Different blocks per participant, help

megancc

Hello,

I'm doing an experiment with OpenSesame (my first time) and I have 3 different blocks with 72 trials each. I want to upload my experiment online so I can reach out to more people (using JATOS and MindProbe).

I would like that it follows this order. First participant does only first block, second participant second block, third participant third block, forth participant first block again and so on.

Is it possible to configure it to do this?

Thank you so much in advance!!

michelescandola

If you use JATOS and OsWeb, it is difficult to put a number for the subject.

In principle, I guess that you might use the sequence element and the "run if" parameter, but...

Why do not prepare just three different experiments, one for each block?

eduard

Hi Megan,

How exactly you retrieve subject numbers from Jatos, I am not sure. However, I suppose eventually you will have some unique value in the variable var.subject_nr With this variable, you can then make the counterbalancing. I attach an example experiment that demonstrates how you could do it. Essentially define three unique blocks, and set them to run never. In a inline_script, you can read out the subject_nr variable (or any other variable you want to use for balancing), and execute the blocks in the correct order.

This example is for Python code only (to illustrate the principle), so not compatible with OSweb. Sorry for that, but I don't know enough about osweb to provide a solution for that.

@Fab I saw in this discussion that you m

opensesame_version.osexp

anaged to access opensesame items with javascript. Do you also whether it is possible and if so, how you would execute a specific item with javascript? Say, you have an item, called block1 , in Openseame you would simply do item.execute('block1') . Can you do something similar with OsWeb? Something like exec(runner._experiment.experiment.items._items.block1)?

Hope this helps a bit,

Eduard

Fab

Hi @megancc,

What you are trying to do is a between-subjects experiment with 3 conditions/groups. With OSWeb, the subject number is assigned randomly by the task based on the settings you indicate in the OSWeb options:

If you want 3 groups, you should set the values to 0,1,2. Then, each time the task runs, it would randomly select one of these values as the subject number.

You can then set up your task with three loops, one of each condition, and set the "Run if" condition of the sequence they're part of to indicate when each loop should be run. For example, you'd indicate subject_nr=0 as the "Run if" condition of one of the loops, subject_nr=1, and subject_nr=2 for the others respectively.

Note that OSWeb does not ensure that you'll get the same number of subjects in each condition/group.

Hope this helps!

Fabrice.