trouble with subliminal presentation times

[jarvis24]

I would just start with excluding all other programs and see if that makes a difference. If not, then there is no point taking hours to isolate one program or another. Here is a link to a freeware (donation optional) utility that you can use to prevent any or all activity during startup:

www.empirisoft.com/support/showthread.php?p=2124

My best guess is that this is an interaction between your particular computer setup there and DirectRT. This is what I was trying to get to in referring you to the trouble shooting section of the user's guide, but I'll try to be more explicit here. Let's try some basic causal attribution:

• Do you have any machines that do not show this behaviour at all or does every one do this at least occasionally? This is a very important question to answer because we can then look to the differences between machines for potential causes of the issue.
• Is there anything about the lab situation that the problem sessions have in common--e.g., time of day, day of the week, experimental conditions, experimenters, etc. Did it start happening around a certain date or has it been happening ever since your origional testing and first subjects? These questions would require some investigative work looking at file dates and times.
• If you disconnect from the network, can you produce these same results? If not, that would imply that the computers are fine and that there is some network interference at work.
• If you do not load any other software or start any other processes aside from DirectRT, can you produce the problem? That would point the finger toward competing processes within the same computer.
• If you run the session in another lab or on a home computer can you produce this problem?
• If you sort log data file by the Order column, do the times in fact occur at predictable times and/or in clusters? If so, are the clusters spaced in time in some predictable way?
• Finally, I don't think I ever saw your style file--what resolution are you running your sessions in (as defined under Options in the style file)?

OK, that's it. This is by no means an exhaustive list of things to check. It's just supposed to illustrate the kinds of things you might think about in the process of trying to figure out what's going on.

Please remember that what you are looking for here is probably not a bug in the software. It is possible for other programs or processes to demand all of your system's processing resources. In such cases, whether it's for 1ms or 1000ms, then DirectRT may not be able to operate during those moments. If that ever occurs, then all DirectRT can do is tell you about in the log file--and you can always count on it to do so.

In fact, I'm curious about one thing. You mention that this happens frequently and on most machines and most experiments.. but that you also test the sessions ahead of time and look at the log files. Are you saying that this never happened during the test sessions and happened only when running actual participants? If so, that would be very useful to know.