Different displays for two interacting participants

phidget · April 2019

Hello helpful people! I am working on designing an EEG/behavioral experiment for two interacting participants, where each trial consists of the following stages:

Stimulus presentation: 4 images with uniform dimensions are shown left-to-right (left-to-right order is different between participants)
Selection: each participant selects one of the four options
Feedback: each participant is shown which image was chosen by his/her co-player

This requires a couple tricks that I'm not sure if/how Open Sesame supports:

Different positions of images on sketchpad shown to different displays (so that the 4 stimuli are displayed in different order for each participant)
Different feedback items shown to different displays (dependent on co-player's response)

Has anyone implemented a similar kind of two-person paradigm in OpenSesame and/or could give me some tips to start with? Or should I be looking at another program to do this?

sebastiaan · May 2019

Hi phidget,

So your essentially wondering how you can show stimuli on two different monitors? Do I understand that correctly?

There are a few different ways to do that, but the easiest is probably to use a dual-monitor setup where you configure both monitors to be on top of each other (in the display configuration, not physically) so that together they make up one very tall virtual screen. Say that both monitors have a resolution of 1280 × 1024, then their combined resolution would be 1280 × 2048.

Within OpenSesame it's then just a matter of presenting all the things that you want to show one monitor on the top half of the screen, and all the things that you want on the other monitor on the bottom half. Does that make sense?

Cheers!

Sebastiaan

phidget · May 2019

Thanks for your reply, Sebastiaan!

Unfortunately it seems that this method doesn't work. When I use a dual-monitor setup to extend the display vertically, and double the resolution vertically in the general properties of my experiment within OpenSesame, then the experiment still shows on only the primary display. Also, OpenSesame only displays the center of the experiment, meaning it cuts off some of the top and some of the bottom of the display (and some of the left and right). The problem persists in different backend settings (psych, legacy, xpyriment). Is there something I'm missing here?

Thank you!

Lionel

sebastiaan · May 2019

Hi Lionel,

The exact behavior depends a bit on the operating system, but I'm fairly you'll find a configuration that works. What if you try the following?

Select the legacy backend
Under backend settings, set Draw window frame to "no" and window position to "0,0"
Now run the experiment in Window mode (so not fullscreen). Because the window has no borders and covers the entire display (if you set the resolution correctly), it will effectively be fullscreen and cover both displays.

> Also, OpenSesame only displays the center of the experiment, meaning it cuts off some of the top and some of the bottom of the display (and some of the left and right). The problem persists in different backend settings (psych, legacy, xpyriment).

You need to set the resolution of the experiment so that it matches the resolution of the virtual screen (so 1280 × 2048 in my example).

Cheers!

Sebastiaan

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