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Thread: Why can I see my subliminal stimuli?

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  1. #1
    Join Date
    Nov 2005
    Posts
    3,328

    Why can I see my subliminal stimuli?

    First thing to do is check out the section in the manual regarding data and the log file--and also the stuff on screen refresh rate in the introduction.

    Also, take a look at the "time n" data columns produced in the log subfolder of the data folder. The log files will tell you after a session what actually happened--as opposed to what you asked for (e.g., if you requested that a picture be on screen for 5ms but it was actually shown for 16ms). This is a nice way of determining if your system can handle what you’re asking for. Note that if you are only displaying stimuli and not taking any RTs you may use negative block IDs (such as -1, -2, etc.) to force DirectRT to write the trial data to the log file.

    With regard to refresh rate, remember that many systems will use a 60hz (16.7ms) refresh rate for many screen resolutions unless you manually set it while in that resolution--and after that Windows will remember it.

    e.g., Let's say you are going to run a session in 800x600 mode (from "Options" in the Style file). You'll need to tell Windows what you want the frequency of the monitor to be for that specific resolution. By default it may be 60hz. To set it to a higher value, go to "Display Properties" in the control panel and set the resolution of the monitor to 800x600. *Then* go to "advanced" and set the refresh rate as high as you can for that resolution. You need to repeat this procedure for any resolutions you plan to run in because most PCs remember display settings separately for each resolution. e.g., if you set the frequency to 100hz for 1024x768, it may still run 800x600 at 60hz, etc.

    Note also, that it is often easier to obtain faster and more reliable display speeds when you use lower resolutions such as 800x600, and when you are using a high quality graphics card on a system with lots of memory (e.g., 512mb+ is usually ok).
    Last edited by jarvis24; 10-31-2006 at 02:09 PM.

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