Positive SOA issue

Gazelle_M

Hi all, 

I’m doing a simultaneity judgment task where participants have to decide whether audiovisual stimuli presented at various SOAs are synchronous or asynchronous. 

Here is a brief structure of the experiment: fixation cross (500 ms) → random jitter (1-750 ms),  auditory beep (12 ms), and circle (15 ms) at SOAs 0, and - 50, 100, 250, 1000 → buffer (250 ms) → response.  

I have successfully created the experiment on OpenSesame but am having issues with the positive SOAs (where the circle precedes the beep). It seems that the AV stimuli at positive SOAs are being presented simultaneously. The negative and 0 SOAs seem to be working fine. 

I’ve included a brief version of what I have so far in the attached document

I would greatly appreciate it if anyone could help me troubleshoot this

sj_help.osexp

Thanks so much 

Gazelle  

eduard

Hi Gazelle,

The problems stems from mixing inline code with Opensesame items. In the inline_script you defined a canvas circle but you don't draw anything on it, so it remains empty and when showing it, the screen doesn't change. Instead you rely on the sketchpad circle to show the visual info. This always follows the presentation of the sound, so logically, no matter the SOA, visual info always trails auditory info. What you need to do, is drawing the circle onto the canvas and get rid of the sketchpad. See the attached example.

sj_help.osexp

Hope this helps,

Eduard

Gazelle_M

Thank you so much for your response. How do I ensure that that circle remains on the screen for only 15 ms before it moves on to the specified SOA? Currently, the circle remains on the screen for the duration of the +SOAs.

eduard

Hi,

circle = Canvas()
circle.circle(x=0, y=0, r=100)
empty_cv = Canvas()
circle.show()
clock.sleep(15)
empty_cv.show()
clock.sleep(SOA)

Eduard

Gazelle_M

Hi again,

Do you know if it's feasible to do a similar thing with a video file? For example, can I present a silent video and a sound file at various SOAs with similar inline script codes?

Can you show me how to show a video using an inline script?

Thanks much

Gazelle

eduard

Hi Gazelle,

For video playback in inline_script you will probably need to use OpenCV2: https://osdoc.cogsci.nl/4.0/manual/stimuli/video/#opencv

I am not sure whether you can, playback a video without blocking the pc. If you can, then the same procedure as with the images should apply to videos. It is somewhat more complicated, but you can try it.

Eduard