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How to record time - not duration - of stimulus onset?

marieke_01 — Wed, 23 Apr 2014 00:39:02 GMT

Hello.

We want to supervise by video if a participant has really observed the presented stimulus. Therefore, we need the time, when the stimulus was presented.

With "stimulusonset" it´s only possible to record the milliseconds after the trail began - thus, a kind of hold-up effect control.

But we need the time - in terms of time of day (10:12:13) or the milliseconds, counted scine the beginning of the whole experiment.

Who can help?

Thank you, Marieke

RE: How to record time - not duration - of stimulus onset?

juhaso — Wed, 23 Apr 2014 00:39:02 GMT

Actually that does not help much. If I find

script.currenttime script.elapsedtime

12:13:23 41291

12:13:33 51391

in my logfile, I know that the trial startet at second 23 and lastet for exactly 10 seconds. However, I don't know exactly when it started. That's to unprecise to sync it with a videorecording of 30 fps which records a frame every 33 ms.

My workaround-solution is to wait for a "full" second:

------------------------------------

### Start experiment-block if second is "full"
### (Inquisit 3.0.6.0)

<expt>
/ subjects = (1 of 1)
/ blocks = [1=loopfullsecond]
</expt>

<values>
/ beginningSecond = script.currenttime
</values>

#########################
### "full second" loop
#########################

<block loopfullsecond>
/ branch = [if (script.currenttime > values.beginningSecond) block.experiment]
/ branch = [if (script.currenttime == values.beginningSecond) block.loopfullsecond]
</block>

#########################
### Experiment starts
#########################

<block experiment>
/ trials = [1=experiment]
</block>

<trial experiment>
/ stimulustimes = [0 = experiment,currenttime1,currenttime2,elapsedtime1]
/ timeout = 5000
</trial>

<text experiment>
/ items = experiment
/ valign = center
/ halign = center
/ position = (50%, 50%)
/ txcolor = (0,0,0)
/ fontstyle = ("Arial", 5%)
</text>

<text currenttime1>
/ items = ("Script start second: <% values.beginningSecond %>")
/ position = (50%, 60%)
/ halign = center
</text>

<text currenttime2>
/ items = ("Current time: <% script.currenttime %>")
/ position = (50%, 70%)
/ halign = center
</text>

<text elapsedtime1>
/ items = ("Elapsed time (should be lower than 1000): <% script.elapsedtime %>")
/ position = (50%, 80%)
/ halign = center
</text>

<item experiment>
/1 = "Experiment starts"
</item>

------------------------------------

The script itself seems to need about 32ms to get up and running on my machine (measured with a very simple script and script.elapsedtime). That's an offset of one frame and acceptable/assessable for me. Nevertheless, a more precise timestamp would be very useful ;-)

RE: How to record time - not duration - of stimulus onset?

Dave — Thu, 17 Apr 2014 07:49:14 GMT

No. The currenttime property does not provide milliseconds. elapsedtime, however, is provided in milliseconds, so if need be you could conceivably combine the two (using math via expressions).

RE: How to record time - not duration - of stimulus onset?

juhaso — Thu, 17 Apr 2014 07:31:11 GMT

Thank you for the very nice possibility, to include a timestamp of the inquisit-events in the logfile via

<data>

/ colums =[...,script.currenttime,...]

</data>

However, to synchronize inquisit-events very accurately with an externally recorded video (with timestamps) it would be very useful to have a inquisit-timestamp including milliseconds, e.g., in the format hh:mm:ss:xxx where xxx are the milliseconds. Is there any possibility to have that?

RE: How to record time - not duration - of stimulus onset?

Dave — Wed, 05 Feb 2014 09:18:32 GMT

You'll want to make use of the applicable 'currenttime' and/or 'elapsedtime' property to record a timestamp /ontrialbegin, log that to the data file and then add stimulusonset to the timestamp to approximate absolute starting time for the given stimulus.