subliminal stimuli

[jarvis24]

To be sure, it can be tricky to get a image to reliably display for a single screen refresh. First check out:

http://www.empirisoft.com/support/showthread.php?t=55

and then if that doesn't help:

http://www.empirisoft.com/directrt/h...leshooting.htm

Definitely Make sure your video system has an up-to-date driver. Make sure you are using the correct driver for your monitor and not a generic driver. And then here are some other thoughts and tips:

The most conservative test is running the input file from a simpler folder on the local hard drive (e.g., c:\test) with the network cable unplugged and no other programs or processes running in the background (one quick indicator of the latter is not seeing any icons in the bottom right corner of the Windows Taskbar--or least as few as possible).

If you continue to get display times that are equal to double your refresh rate then try running the session in 800x600 resolution (as set in the Options of you .drt style file). Also check to make sure the stimulus in question is not the very first stimulus of the trial--that can cause trouble on some systems (in which case a brief blank screen can be used as an initial stimulus).

If you have checked all this (including the links above) and still can't get display times equal to a single refresh, send a zipped copy of your experiment folder to us at support@emp...com and we'll take a look at it.

[normanp]

I need to use a subliminal exposure time but can't get anything below 2 refreshes (33 ms at 800X600, 60Hz). I've been using a modified version of the new input file template ("untitled.csv"). I simply added a fixation point ("*") for 250ms followed by a "subliminal" word prime ("prime") for 15ms followed by the default "cat" and "dog" (rt:any). The log file shows a 33ms exposure time rather than the 15-17ms time I need. I've set the default style to 800x600. I've checked that my systems have a recent version of DirectX installed (9.0). I've tried specifying 15ms, 16ms, and 17ms. DirectRT clocks my refresh rate at 16.96ms or 58.96Hz. I have DirectRT version 2008.1.0.11.

I've attached the following:

DxDiag.txt
untitled.csv (the input file)
1_log.csv (the log file)

Please let me know what else I can try.
Thanks,
Norman

[jarvis24]

What a dream post, Norman--all the info I could possible want and you have checked out all the relevant posts--nice

Unfortunately, I don't see a convenient answer for you. Your files are in perfect order and we ought to be seeing 16 or 17ms on the "prime" trials in your log data files (and of course, we are obviously not).

A few thoughts though..

1. Try specifying 10ms, just in case there is some doubt in DirectRT's mind that your system can handle 15-17ms. This might show it that you are very serious about the single refresh.

2. I noticed a couple red flags in your dxdiag.txt file:

Card name (Chip Type): Mobile Intel(R) 965 Express Chipset Family
Monitor: Plug and Play Monitor

Graphics chips built into the motherboard are a frequent cause of a system's inability to handle demanding display requests. I presume this is a laptop? If so, maybe you could look into seeing if there is a way to upgrade your graphics system either internally or externally (usb2 graphics card?).

I also noticed your monitor is not explicitly defined--you might find it helpful to specify it in the Windows display properties.

Finally, I noticed that it said that the DirectX display tests were canceled before completion--was there a reason for that?