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Thread: Response window IAT

  1. #1
    Join Date
    Jan 2007
    Posts
    26

    Response window IAT

    I am running a response window Implicit Association Test, and I was wondering if there is a way to allow participants to respond before or after a stimulus disappears from the screen. I have found something that is close to this, but it has one big problem. I’ve used the following code:

    stim loc time stim loc time stim

    HomemakerGood-
    WorkingwomanBad 0,0,1 0 $homemaker 0,0,0 rt:18,23,clear675 *


    This code puts the categorization labels (Homemaker & Good) and (Working Woman & Bad) at the top of the screen, and then presents the picture or adjective, which is cleared after 675 milliseconds. So, far this is what I want. Participants can respond during or after the picture/adjective disappears. The problem occurs with the “clear” function. This clear function clears the entire screen and replaces it with a black screen. So, if participants do not respond within 675 milliseconds, they see a black screen, and importantly, they can no longer see their response options (homemaker & good, or workingwoman & bad) on the screen. Is there any way to clear just the picture/adjective stimulus and not the categorization labels? Or, instead of clearing the screen, is there a way to add something to mask the picture/adjective?
    Last edited by Trevor Newell; 06-08-2009 at 10:00 AM.

  2. #2
    Join Date
    Mar 2009
    Posts
    401
    Hm. It would be a bit more challenging to figure out a proper way to complete this task using clear or '1'. The best approach may be to simply cover the appropriate areas up using an image that is the same color as the background.

    Does this make sense?

  3. #3
    Join Date
    Jan 2007
    Posts
    26
    I've tried the approach that presents an image that is the same color as the background, but I've only been able to do this by presenting the main image for a set RT (675 ms), and then having the "background mask" as another stimulus with an RT:18,23. The problem with this approach is that participants can easily respond before the main image is finished being presented (675 ms), but the image doesn't go away upon their response. This confuses participants, and they try to respond a second time while the image is still on the screen, which messes them up for the next trial. Am I stuck with this option?

  4. #4
    Join Date
    Nov 2005
    Posts
    3,323
    A couple "work-around" options in order to use the "overwrite the image" approach. If the late response (>675ms) can be expected within a second window for 675ms--i.e., and overall RT of 1350ms, then you could eliminate the clear675 function and instead use a minmax value of 0-675! for the style on that trial. That would cause automatic continuation from the first opportunity to respond to the second. Importantly for your purpose, you would not have to clear the screen between stimuli--you could simply cover the initial image but no the labels. In your subsequent data crunching, you would then need to add the two RTs together. This raises again the issue though of what you want to happen if they *do* respond in the first 675ms. Do you want an overall fixed response window of 1350ms? Or do you want them to continue to the next trial immediately? If the latter, then you could put a skip function in for each response that exits them from the trial immediately to the next. Let me know if you'd like elaboration on any of this or if it's not what you are looking for.

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