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Thread: Help with Subliminal Priming

  1. #1
    Join Date
    Feb 2010
    Posts
    2

    Help with Subliminal Priming

    Hi,

    I am using DirectRT (version 2006) to run a task to subliminally prime an Image, but the problem is, everyone can see it!

    I have the image programmed to only flash for 16ms. I checked the Log, and quickest the image will flash is 30 or so ms. (I tried programming it for 8ms, but this didn't do much either). I followed some tips that I found in the DirectRT forums; I changed the display in the options menu from the style file to 800X600, but this did not solve the problem. I then went and changed the computer monitor to 800X600 ms, but that didn't work and unfortunately I could not make the monitor go faster that 60hz. (I am using a thinkpad). I also made sure not to have any other programs running at the same time.


    I used to think it was because it was on a rather old laptop but I put the task on several other computers and the same thing keeps happening. If you could help me out I would greatly appreciate it!!

    I have attached the CSV filewith the images so the task can work if you need/want to run it. Thanks so much for your help in advance!

    Jenny
    Attached Files Attached Files

  2. #2
    Join Date
    Nov 2005
    Posts
    3,321
    I could open your log file but not the input file--can you double check that it was the correct input file?

    In any case, looking at your log file it appears you have an initial stimulus that appears at the same time as the subliminal stimulus, yes? And then you take the RT?

    If so, try a small modification whereby something occurs at the start of the trial other than the subliminal stim--e.g., a fixation stimulus like "XXXXX" for 100ms. And then, the rest of your trial...

    It doesn't need to stay that way, I would just try that to see if it affects your likelihood of achieving 16ms. On some systems, 16ms (or less) can be hard to achieve on the very first stimulus presented within a given trial.

  3. #3
    Join Date
    Feb 2010
    Posts
    2
    Thanks so much for your response.

    I have attached the input file again. Hopefully it will open this time.

    If it doesn;t work, here is a little more detail about what the task does (or is supposed to do):

    yes, there is a stimulus that appears at the same time as the prime, but then the primed image is masked by a third stimulus. In other words, a red dot appears in the middle of the screen at the same time the prime is flashed above or below the dot followed quickly by a masking stimulus. (Subjects are told to press one key if the Image appears above the red dot and another key if the Image appears below the red dot--- the only image they are supposed to see is the masking stimulus).

    Anyway, I will follow your suggestion and put a fixation stimulus first, and let you know what happens! Thanks again for your help,

    Jenny
    Attached Files Attached Files

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