Millisecond Forums

Hi all,

I have a procedure that involves presenting a number of trials with different set sizes of images (i.e., on some trials, the participant sees 8 images, on others they see 36, etc.).
In the task I have a value that I have set to reflect the elapsed time (time_passed) since the beginning of the procedure, and at the beginning of each trial I update this value.
I also have information relating to the duration of the trial overall. However, these values don’t seem to balance. For example, if values.time_passed = 2000 on Trial X, and Trial X’s duration is 2000, I would expect that the value of time_passed on Trial X+1 should be 4000 (or maybe 4001). However, there’s a discrepancy between these values. For example, values.time_passed at the beginning of Trial X+1 will actually be something like 4025 or 4014 (so also no constant delay). This is an issue because I am using EEG, so precise timing is crucial.

I think that the problem may lie in the fact that multiple images have to be loaded simultaneously, and there’s some buffering time for loading these images.
1.       Is it possible that loading these images could cause this kind of lagging effect?
2.       If so, is there any way that I can overcome this issue (for example, in E-Prime, you can “pre-release” images at the beginning of the procedure to prevent lagging)?

Thanks in advance,
Danna