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Recording Response time with first keypress

I am fairly new to OpenSesame, but I am currently working on a predicted motion experiment, where the participant sees video where a ball moves from left to right but disappears behind and occlusion. The participant then has to click the Spacebar at the moment he/she expects the ball to reappear from behind to occlusion. My issue is that the trial does not stop on the first keypress but requires two keypresses to move on, and the response times it captures don't match up with the length of the trials. The experiment itself works, its just the data collection that I am having issues with. Thank you!


  • Hi,

    My first thought is that you're simply collecting two key presses, for example because you have inadvertently set the duration of a sketchpad to 'keypress', in addition to collecting a key press response during the trial. If that's not it, could you attach the experiment here so that we can take a look?


  • edited November 2018

    Hi Sebastiaan,
    I attempted to remove the keypress for the sketchpad, but ideally I would like the trial to terminate when the key is pressed. Its not the end of the world if it doesn't work out that way but that's what I was shooting for. Ideally, I want the trial to start and the person to hit the spacebar at the expected time. The trial will terminate recording the timing of the keypress and move on to the next trial. I appreciate your help with this.

  • Hi Timothy,

    What Sebastiaan suggests should not lead to the trial not being terminated on a key press. It just makes sure that your keyboard response is handling the keypresses and not the sketchpads. Anyway, I can't find any sketchpads in your experiment, so I can't really check. Is it possible that you use the media player? Is there an option in there to set the duration of it to 0? As far as I can tell, this would solve the issue.


  • Yes that is correct. I play a video with the media player and during the video they need to press a key to record their response time. It seems that when I set the duration of the media player to 0 it doesn't play at all. Thanks for your help

  • The beginning of the clip stays frozen on the screen, to clarify.

  • What media player do you use? Can you maybe send a screenshot?

  • of the video?

  • I am using VLC media player

  • Of the VLC media player interface in Opensesame.

  • Is this what you meant?

  • This is what my media player screen would look like

  • Do you have any suggestions on how I might record the response times during these video displays?

  • I haven't used this plugin and maybe I'm terribly wrong, but could the problem be in the "Call custom Python code on keypress" item? Looking at the script, it seems that it will jump to the custom code when the field is not empty. Obviously, there is nothing in the code, so it will "jump back" to the main window, but I have an inkling that that explains why two keypresses are required.

    What happens if you leave that menu blank and put keypress as the Duration?

  • This seemed to work! Thank you! Also, is the response time recorded in ms?

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