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Collect keyboard response only on specific trials


I was wondering if there's any way to set the keyboard response to only collect keypresses on some trials? For my experiment, participants need to respond with a keypress only if they see the target appear at certain positions on the screen (top or bottom), but not if the target appears anywhere else. The location of my target is pseudorandomised with the inline script and the order of locations change every block, so I can't use the block loop to specify the correct response.

I hope I'll be able to get some help on this. Thanks! :smile:


  • Hi everyone,

    I'm still stuck on this problem, wondering if anyone can help? Basically I just need the keyboard response to only work on trials when the target is in certain positions on the screen, and to not leave a response time for other trials. Thanks!

  • Hi Hannah,

    Why would you want that, if I may ask?

    If you have a variable that codes the target location (response_required vs. response_not_required or something like this), you can put this into the run if statement of the keyboard item and run it only with a response is required. I think this should do the trick, but it's possible that there will be some weird side effects.


  • Hi Eduard,

    I was trying to see if there was any way to decouple the keyboard response time and the stimulus presentation time, as participants were only supposed to respond on certain trials, and the additional keyboard response time at the end of each stimulus presentation was making the experiment last too long overall. I eventually managed to solve that by changing my sketchpad duration to 0 and setting the keyboard response time to the stimulus presentation duration, and it works fine. Thanks for your help!

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