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Thread: Interstimulus timing

  1. #1
    Join Date
    Feb 2009
    Posts
    11

    Interstimulus timing

    We are designing a cueing experiment with a visual search array. After presenting the fixation stimulus and the location cues, there is an ISI of 250 ms before presentation of the search array (which varies in number from 5 to 12). We have noticed when we actually run the file, the ISI is not 250 ms, but closer to 1000 ms. I realize that this is likely due to issues of drawing the array, but I need to overcome this and have an ISI of 250 ms. Any suggestions? I have attached the file.
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  2. #2
    Join Date
    Feb 2009
    Posts
    11

    ISI timing and drawing stimuli

    Can someone help me fix this issue of directRT (or perhaps it is my hardware) add at least 700 msec to the ISIs of my trials? I need to have an ISI of ONLY 250 msec. This is what we enter in the file, but this is not what we get -- we get over a 1000 msec ISI.

    WHAT IS CAUSING THIS? HOW DO WE FIX THIS? HOW DO WE ENSURE THAT WE GET THE ISI TIMING THAT WE INPUT?

    HELP -- URGENT!!!!

    Scott

    Quote Originally Posted by sadler View Post
    We are designing a cueing experiment with a visual search array. After presenting the fixation stimulus and the location cues, there is an ISI of 250 ms before presentation of the search array (which varies in number from 5 to 12). We have noticed when we actually run the file, the ISI is not 250 ms, but closer to 1000 ms. I realize that this is likely due to issues of drawing the array, but I need to overcome this and have an ISI of 250 ms. Any suggestions? I have attached the file.

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