Millisecond Forums

You need to do that by calling the insertstimulustime() function /ontrialbegin:

<expressions>
/ rand_onset = round(rand(800,1200))
</expressions>

<values>
/ current_onset = 0
</values>

<trial mytrial>
/ ontrialbegin = [
values.current_onset = expressions.rand_onset;
trial.mytrial.insertstimulustime(text.s2, values.current_onset);
]
/ ontrialend = [
trial.mytrial.resetstimulusframes();
]
/ stimulustimes=[0=s1; 1400=instructions]
/ validresponse = (57)
</trial>

<text s1>
/ items = ("s1")
/ position = (50%, 40%)
</text>

<text s2>
/ items = ("s2 @ onset <%values.current_onset%>")
/ position = (50%, 50%)
</text>

<text instructions>
/ items = ("instructions")
/ position = (50%, 60%)
</text>

<block example>
/ trials = [1-10 = mytrial]
</block>

Hi Dave,

That's a really helpful reply thanks so much!

I have another related question that I was wondering if you or anyone else knew the answer to. My experiment uses audio files as stimuli, and the onset of these stimuli isn't synchronised with any events happening on the monitor. It's a temporal perception paradigm so timing is a crucial element of the experiment. The help docs say this about the "insertstimulustime" function:     

"Adds the stimulus to the frame of a trial corresponding to the specified time."

My question is does Inquisit still trigger the audio file at the time of the beginning of the next frame if the stimulus is not being presented on the monitor or is it able to place the stimulus at exactly the time indicated by the output of the rand expression?

Thanks

Andrew

The timing would still be locked to the frame, even for non-visual stimuli.

I see thanks Dave.
One last question if you don't mind. I was wondering if you or anyone else reading this knows of any background processes like antivirus software or automated Window maintenance operations that have been found to affect timing in Inquisit?
Andrew

Generally no, it's fine to have regular processes running in the background on a decent machine and those will not affect timing. If you are on an extremely resource-constrained system, however, e.g. with little RAM, then it may make sense to minimize the amount of background processes if you're in a position to do so (i.e. the machine in question is an offline lab machine under your control). Hope this helps!

Yes that's exactly what I wanted to hear thanks!