Stimuli/ Triggers/ Timing difficulties

[David McFarlane]

Perhaps I can clarify this point a bit further.  As discussed at 
http://groups.google.com/group/e-prime/browse_thread/thread/39e899d3457d4917 
, StartTime indicates the time at which E-Prime started to *execute* 
the *code* for the stimulus object.  In many cases, that code 
includes operations such as waiting for a screen refresh, etc., so 
you may find a considerable delay from StartTime to OnsetTime 
(although 575 ms does seem excessive).  OnsetTime, as stated before, 
indicates the time at which E-Prime  actually submitted the stimulus 
data for *presentation*, and that is the time that interests you in 
this case.  And your OnsetSignal trigger should occur at the 
OnsetTime of your stimulus, but if you really want to verify this 
then you need to get out an oscilloscope and measure it.

For future reference, note that the various time audit measures take 
place in the order in which I presented them in the thread linked above.

-- David McFarlane


At 5/8/2012 02:38 PM Tuesday, Douglas wrote:
>4-...
>About StartTime and OnsetTime, I remember what you said and what I
>looked for was:
>OnsetTime>>Timestamp at which the object begins its critical action
>(e.g., drawing to the screen).
>StartTime>> Timestamp at which execution for the object began
>(i.e.,time at which the Run method began to execute).
>
>So, I guess logically OnsetTime should come before StartTime... That's
>why I don't get this:
>                 Stimulus.OnsetTime: 33523
>                 Stimulus.PreRelease: 400
>                 Stimulus.Duration: 489
>                 Stimulus.StartTime: 32948
>
>But this is what PST Technical Consultant Told me:
>  "OnsetTime represents the time the object was actually presented.
>StartTime can occur before    OnsetTime and should not be used for
>measurements."
>
>Now, if we have a huge difference between Stimulus StartTime and
>Stimulus OnsetTime, there should be such difference between Trigger
>StartTime and Trigger OnsetTime, IF such thing exists at all! And If
>it does exist, Which one are we measuring?!

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