<HTML><FONT FACE=arial,helvetica><HTML><FONT SIZE=5 PTSIZE=18 FAMILY="SERIF" FACE="Times New Roman" LANG="0">Help with inspection time.<BR>
<BR>
Greetings.<BR>
<BR>
I am interested in using the inspection time task uploaded onto the eprime website by Paul Groot. I'm having two problems (and I am not at all versed in programming) that I was hoping someone here could help me with.<BR>
<BR>
1) The experiment is written for 100hz monitors. I only have access to machines with 60hz monitors. As far as I can tell from the code, it seems like running in 60hz would be do-able, but I lack the expertise to know if the experiment would still produce reliable data running at 60hz.<BR>
<BR>
2) There's a section of the code that I cannot grasp. Briefly, in the inspection time task, two lines are presented, and the subject decides which one is longer. The lines remain on screen only for a short period of time. The duration for the next trial changes whenever a "reversal" occurs. For example, if the subject gets 4 right at the current duration, a reversal occurs, and the duration time is decreased (making the task more difficult) by a set amount for the next trial. Conversely, if the subject gets this trial wrong, a reversal also occurs, and now the duration time for the next trial is increased.<BR>
<BR>
The duration time for any trial is just the refresh interval of the monitor (10 ms for 100 hz, or 16.67ms for 6 hz, as with my monitor) x the number of frames. For example, the first trial has 10 frames, so the stimulus remains onscreen for 100ms (100hz) or 167ms (60hz). If the subject gets 4 right at this duration, the number of frames is "stepped down" by 4. So, the next trial would have 6 frames and the stimulus would last for 60ms. The step sizes decrease in later trials to hone in on the subjects true "inspection time".<BR>
<BR>
When I run myself as a subject, though, the data file seems off. Sometimes when I do 4 right at a given duration, the number of reversals does not go up by one (even though the next trial presents the stimulus at a shorter duration). Other times, 4 right at a given duration does result in a reversal.<BR>
<BR>
The same is true with mistakes-- sometimes eprime will record the reversal, and the duration for the next trial will increase; other times, the reversal is not recorded in eprime, even though the next trial does have an increased duration. Here's the relevant (I think!) part of the code:<BR>
<BR>
if nOK>=REAVALUATE_CORRECT_COUNT then<BR>
' decrease stim duration<BR>
nOK = 0 ' restart counting<BR>
if (nPrevFrameCount < nFrameCount) then nReversals = nReversals + 1<BR>
nPrevFrameCount = nFrameCount<BR>
nFrameCount = nFrameCount - nStepSize<BR>
if nFrameCount<=0 then <BR>
nStepSize = nStepSize \ 2<BR>
if nStepSize<1 then nStepSize=1<BR>
nFrameCount = nStepSize<BR>
end if<BR>
<BR>
The fourth line makes no sense to me. I have 4 correct trials in a row, so I should get a reversal (the next trial should present the two lines at a shorter duration). But how is it that the previous frame count could be less than the current frame count. Shouldn't it be the opposite (the previous frame count was higher-- the lines were displayed longer-- than the frame count for the current trial).<BR>
<BR>
Sorry for the length of this post, perhaps I should stop here. If anyone could help, I would sincerely appreciate it.<BR>
<BR>
Bryan<BR>
<BR>
</FONT></HTML>