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Thread: using prior random stimuli

  1. #1
    Join Date
    May 2007
    Posts
    2

    using prior random stimuli

    Hi,
    I worked my way through the manual to create the attached procedure for a general memory test - a new/old test.

    My goal is to use reuse randomly generated stimuli from block 1 in block 2.
    Althogh I checked the drt's sample and it looks the same, drt displays text that it can not find the stimuli (I use v2008).
    Also, is there any way that in block 2 i can add to the previously randomly generated stimuli from block 1, more random stimuli from the same type of stimuli but not those used in block 1?
    Pleast let me know where is the failure in the attached.
    Thanks,
    Gadi
    Attached Files Attached Files

  2. #2
    Join Date
    Nov 2005
    Posts
    3,328
    Hi Gadi,

    Maybe it's something else, but I did notice first off that your comment (!) columns appear before you block and trial columns. This would certainly be a possible cause for the input file not running properly. Try inserting them after the block and trial columns (see "comment columns" in the users guide) and see if that helps. If not, let me know and I'd be happy to look into it further.

  3. #3
    Join Date
    May 2007
    Posts
    2

    it works but..!!

    Great!!
    Thanks Jarvis!!
    Can't beleive it was as simple as that..

    But, I do have two follow up questions.
    My paradigm is a memory task: subjects need to recall in block 2 which stimuli where presented in block 1, detecting if the stimuli is new or old.

    As you may see there are 16 stimuli to be memorized in block 1. In block 2, in addition to the previous 16, there are 16 more which are randomly selected from the same lists. I cant really now this for sure, but I ran the paradigm 3/4 times, and it seems that DirectRT randomly chooses the additional 16 from the stimuli list, avoiding the ones which were selected in block 1 (and recalled in block2 by using the '?'). Is this indeed so or just chance? Is it possible that one of my subjects might indeed encounter the same stimuli twice - once when recalled from block1 and once when randomly selected again in block 2?

    My second question is a little more complicated. In fact, in order to avoid fatigue, im separating my stimuli into 2 tasks. So immediatley after the second test block I would have another 16 stimuli to be memorized and then recall them at another test block. Is there any possibility to avoid using the stimuli which were already used in block 1 & 2?
    I.E. that in block 3, 16 more stimuli will be randomly selected, none of which are from the 32 stimuli already used in the first 2 blocks, and that block 4 will use as test the final batch of 16 stimuli from my total 64 in the list?

    I hope my explanation of the questions is clear.
    Looking forward to receive your answers.
    Gadi

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