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Thread: Collecting responses during trial interval

  1. #1
    Join Date
    May 2006
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    12

    Collecting responses during trial interval

    I have stimuli that are displayed on the screen for 400 ms with a 1600 ms ISI (blank screen) between stimuli. I want to be able to record responses to the stimuli, but without interfering with the display durations. So under time I have rt:57,full and have a minmax of 0-400! and a trial interval of 1600 ms. However, I want to be able to record responses anytime between when the stimulus is shown and before the next stimulus appears just in case the subject is slower to respond and makes their response after the stimulus disappears but within the trial interval.

    This is my first experience with DirectRT and I would appreciate the help!

    Rachel

  2. #2
    Join Date
    Nov 2005
    Posts
    3,328
    Rachel,

    Check out the section called "Clear Screen During an RT" in the user's guide. In your case, I think you could use something like "rt:57,full,clear400" with a min-max value of 0-2000! for the trial. Here is a link to the section from the guide online:

    www.empirisoft.com/directrt/help/directrt_samples_of07_clear_screen_during_an_rt.ht m
    Let me know if that doesn't do it.

    Blair

  3. #3
    Join Date
    May 2006
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    12
    Unfortunately this didn't work. The subject won't be responding to every stimulus. Using your suggestion, the program leaves the stimulus up for 2000 ms on those trials which there is no response.

  4. #4
    Join Date
    Nov 2005
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    When you use "rt:57,full,clear400" does the stimulus not disaapear after 400ms?

  5. #5
    Join Date
    May 2006
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    12
    I'm sorry. I don't know what I did wrong the first time but now it's working. I do have one additional problem now, however. It's my understanding that the trial interval specified wouldn't occur until after the 2000 ms is up. I would like each stimulus to appear 2000 ms following the previous (400 ms stimulus, 1600 ms blank screen, 400 ms stimulus, etc). However, since I would like to record responses during that 1600 ms blank screen, it seems that I will have to add more time between trials for the trial interval. Is this correct?

  6. #6
    Join Date
    Nov 2005
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    In this case, if you changed your trial interval to say 200ms, then you could use "rt:57,full,clear400" with a min-max value of 0-1800! for the trial. You need some trial interval because that's when DirectRT prepares the next trial. If, for example, your standard trial interval is set to 200ms, then adding a total trial duration of 1800ms would produce 2000ms between trial onsets. You could also try a trial interval of 100ms and a min-max value of 0-1900! etc. Does that make sense? Note though that DirectRT will not accept a response during the trial interval, so in the latter case, you would be looking at 1900ms of response time potential.

  7. #7

    Will this work with an old version?

    I was actually about to ask this same question, and this looks like it might answer it for me. However, since my lab is cheap, we're still running v2002. Will this work with this old version?

    Thank you!

  8. #8
    Join Date
    Nov 2005
    Posts
    3,328
    I don't think so, I believe the clear function was added at some point during the 2004 version.

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