Simple cumulative timing question

[David McFarlane]

First & foremost, you can figure this out by doing some test for 
yourself (and you should never believe what anyone tells you 
anyway).  Just run your exercise and inspect all the time audit 
measures (see 
http://groups.google.com/group/e-prime/browse_thread/thread/39e899d3457d4917 
) from your various stimulus objects.

Of course, you still want some theoretical understanding.  For that, 
start with Chapter 3 of the original E-Prime User's Guide (or try 
Chapter 4 of the revised edition).  Then look at the 
GetNextTargetOnsetTime and SetNextTargetOnsetTime topics in the 
E-Basic Help facility.  From that, let's infer that E-Basic holds a 
hidden NextTargetOnsetTime variable.  And note that Timing Mode 
merely determines the baseline for setting NextTargetOnseTime from 
the stimulus Duration -- i.e., Event uses OnsetTime for the baseline, 
whereas Cumulative uses NextTargetOnsetTime (or TargetOnsetTime, 
depending on how you want to think of this).  From there, it is just 
simple arithmetic.

So suppose you have an InLine, followed by Slide1 (set to Cumulative 
timing mode), followed by Slide2.  And suppose that Slide1 one does 
*not* get terminated by some event (e.g., response or sound End 
Action).  In that special case, the following holds:

When Slide1 starts execution,
     Slide1.TargetOnsetTime = NextTargetOnsetTime
     NextTargetOnsetTime = NextTargetOnsetTime + Slide1.Duration

Then when Slide2 starts execution,
     Slide2.TargetOnsetTime = NextTargetOnsetTime
     ...

So from that you can see that, yes, what you surmised was 
correct.  By contrast, using Event timing mode, the following would hold:

When Slide1 starts execution,
     Slide1.TargetOnsetTime = NextTargetOnsetTime
     ...
     NextTargetOnsetTime = Slide1.OnsetTime + Slide1.Duration

And you can take it from there.

BTW, why not just use Cumulative timing mode for all your stimulus 
objects in the Procedure?  In most cases, that would seem more natural.

And again, test all this for yourself, never take anyone's word for 
anything, not even mine.

-----
David McFarlane
E-Prime training 
online:  http://psychology.msu.edu/Workshops_Courses/eprime.aspx
Twitter:  @EPrimeMaster (https://twitter.com/EPrimeMaster)

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At 11/6/2012 08:56 PM Tuesday, FrankBank wrote:
>I just want to make sure that I understand how the cumulative timing 
>works. For example, say you had a trial procedure with several 
>slides but that began with an inline that was causing onset delays 
>(for the first slide).  Then you could set the timing of that first 
>slide to cumulative and the delay will be  absorbed by that slides 
>total duration time setting.  Meanwhile, the rest of the slides in 
>the procedure can be left on the event timing setting, since they 
>have no onset delays.  So, as long as the first slide is, for 
>example, just a blank pause or something, then cumulative timing 
>would work well because the total blank screen time would remain the 
>same at the beginning of the procedure.  Do I have this right?
>
>thank you for any assistance/reassurance!

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