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Join Date: Mar 2007
emcog is on a distinguished road Posts: 4
Stimulus presentation error, Posted June 4th, 2007 #1

My program contains a trial with the following events:

Event 1: Text, correct response is space bar
Event 2: Movie, no response can be made
Event 3: Text, correct response is string


Everything proceeds as planned , except event 1 flashes on the screen for a second just prior to event 3. Any ideas on what is causing this?

  • In "Participant Input," I made sure to indicate that single-key responses are accepted only by events looking for single key responses (and string responses only by events looking for string responses).
  • Events 1 and 3 are set to "end the event and move to the next one" only after receiving a correct response. Event 2 is sent to end immediately after the movie finishes playing.
  • There are no stimulus lists involved.
  • All events are set to erase the screen before proceeding.
  • The trial is NOT set to randomize the events.

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Join Date: Aug 2006
Location: San Pedro, CA
Hisham is on a distinguished road Posts: 1,214
Posted June 9th, 2007 #2
Hi Lisa,

It's hard to tell without seeing the experiment, but I don't believe that the movie event type provides an option to erase the screen before playing the movie, which means that event 1 will stay on the screen until event 3 is presented.

Does this seem like your problem?

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Join Date: Aug 2006
Location: Asheville, NC
Hank is on a distinguished road Posts: 490
Posted June 11th, 2007 #3
Movies don't have the option to erase the screen.

On OS X, the canvas that pictures and text are drawn onto is completely independent of how movies are drawn. A movie playing on the screen does not affect what was already there. This is why Event 1 is "flashing" on the screen. To get rid of this effect, tell Event 1 to erase the stimulus at the end of the event. This is a new feature as of 4.0.3, and it's in the picture/text settings dialog under the Presentation Options tab. This will erase Event 1 at the end of Event 1, so it won't be visible anymore when Event 3 comes up.

I hope this helps!
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Join Date: Apr 2015
krnaish is on a distinguished road Posts: 12
how to erase movie after it ends, Posted April 10th, 2015 #4

I think I have a similar problem. The structure of my trials is as follows:

1) Fixation cross
2) Movie 1 (300ms; allow to play until end but allows other events to continue before the end of the movie, because I present an external stimulus during the movie)
3) Mask (visual white noise, 500ms; allow to play until end, does not look for input until end of event)
4) Movie 2 OR static image (300ms; wait for any response from participant before ending)

This seems to works fine if the 4th event listed is a movie (although not on every computer I have run it on). However, if it is a picture file, it does not display. If I change the location or the size of the picture file, it is clear that the image does display, but it is hidden behind a white square left by the movie file. Is there a way to erase the movie stimulus completely once it has finished playing? Assuming that is the problem.

Many thanks.
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Join Date: Aug 2006
Location: San Pedro, CA
Hisham is on a distinguished road Posts: 1,214
Posted April 15th, 2015 #5
Please let me know if the workarounds that we discussed over the phone do not help.
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