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Thread: having the computer create variable interstimulus intervals

  1. #1
    Join Date
    Oct 2006
    Posts
    12

    having the computer create variable interstimulus intervals

    [edited by moderator]
    I am trying to design a task in which I give all subjects the same total duration, e.g. 60 stimuli in 120 seconds--but to vary the ISI between stimuli across subjects. I do not know how to do that in DirectRT. I would really appreciate if you could get back to me in this matter.
    thanks
    maya .
    Last edited by jarvis24; 11-05-2007 at 10:30 AM.

  2. #2
    Join Date
    Nov 2005
    Posts
    3,309
    You can use a constant interval in the style (.drt) file but add a blank stimulus to the end of each trial in your input file, like this:

    stim = ~
    loc = 1,1,1
    time = 500

    That would give you a 500ms ISI for that trial. For a 300ms ISI, you simply change it to:

    stim = ~
    loc = 1,1,1
    time = 300

    And so on. You can also have these values be random, or randomly chosen from a set. For that see, www.empirisoft.com/directrt/help/directrt_using_random_values.htm

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