Mastering E-Prime: Meaning of all time audit measures.
Sylvain
symadec at gmail.com
Sun Feb 24 14:49:10 UTC 2013
David and Scott,
Thank you for your answers. I need to be reassured. When doing EEG
experiment, I always run an inline before the object I want to trigger(maybe
I could even do that at the top of the procedure I guess). Let's call this
object StimEEGa,d the trigger 50.
What I always did was an inline like:
StimEEG.OnsetSignalEnabled = True
StimEEG.OnsetSignalPort = &H378
StimEEG.OnsetSignalData = 50
StimEEG.OffsetSignalEnabled = True
StimEEG.OffsetSignalPort = &H378
StimEEG.OffsetSignalData = 50
If I understand correctly This inline tell "wait for the object StimEEG to
run and send the signal'. By running I mean waiting for StimEEG to be drawn
on the screen right, independantly of any pre-release ? On the e-prime
side, does this correspond to StimEEG.OnsetTime?
Thank you,
Sylvain
On Friday, February 22, 2013 6:42:29 PM UTC+1, McFarlane, David wrote:
>
> Sylvain,
>
> At 2/22/2013 06:36 AM Friday, Sylvain wrote:
> >Hi David,
> >
> >I have a question regarding to pre-release and timing.
> >
> >I did a little experiment trying to get the timestamp of the onset
> >of stim, and the offset or it.
>
> Wonderful, everyone should do these sorts of explorations (that's how
> I figured out all this stuff).
>
>
> >It's simple basically i have :
> >
> >- Inline1: I collect t1 = Clock.ReadMillisec
> >- Then an ImageDiplay for 200 ms with a pre-realase equal to the
> >duration of it. I log the onset of ImageDiplay and the offset of it;
> >- Inline 2: I collect t2 = Clock.ReadMillisec
> >
> >Doing that, basically I get t2-t1 almost equal to 0 modulo some refresh
> rates.
> >I also get ImageDiplay.OnsetTime = ImageDiplay.OffsetTime.
>
> As you should. You might find OffsetTime slightly behind OnsetTime;
> and under these conditions (PreRelease = Duration), you should find
> that TargetOffsetTime = TargetOnsetTime without exception.
>
>
> >1) There's something there that I don't really understand, which
> >timestamp should I really consider, ImageDiplay.OnsetTime or
> >ImageDiplay.OffsetTime?
>
> That depends entirely on what you wish to do with that timestamp.
>
>
> >2) If I understood pre-realase affect offset time, so does that mean
> that:
> >ImageDiplay.Duration = (ImageDiplay.OffsetTime
> >- ImageDiplay.OnsetTime) + pre-realase
>
> Not quite -- E-Prime can control only *Target* offset (& onset)
> times, not actual times. Actual offset (& onset) times are subject
> to the limitations of the stimulus presentation hardware. Also, I
> would not write the relationship that way -- that makes it sound like
> Duration derives from the other quantities, which is wrong. As I
> described earlier, Duration remains whatever you asked it to be, so
> should appear only on the right side of the equals sign as it is used
> to determine other quantities. Thus, repeating what I wrote in my
> earlier description of TargetOffsetTime, in the case of Event timing mode,
>
> ImageDisplay.TargetOffsetTime = ImageDisplay.OnsetTime +
> ImageDisplay.Duration - ImageDisplay.PreRelease
>
> Note that, in the case PreRelease = Duration (the new default setting
> since EP2.0.10.x), we get simply
>
> ImageDisplay.TargetOffsetTime = ImageDisplay.OnsetTime
>
> which fits your observations. If instead we set PreRelease to 0, we find
>
> ImageDisplay.TargetOffsetTime = ImageDisplay.OnsetTime +
> ImageDisplay.Duration
>
> which perhaps is what you expected (and was the default for Event
> timing mode prior to EP2.0.10.x).
>
> And just to drive the point further, OffsetTime does *not* indicate
> the time at which *presentation* of a stimulus ends. Rather, (for
> most practical purposes) it indicates when *execution* of the
> stimulus Run method ends (strictly speaking, this describes
> FinishTime, see my earlier description for the fine distinction
> between OffsetTime and FinishTime).
>
> Furthermore, even with PreRelease set to 0, neither Duration nor
> (OffsetTime - OnsetTime) necessarily indicate the actual duration of
> the stimulus. In particular, a visual stimulus does not disappear at
> its OffsetTime (ignoring Clear After, which has been deprecated), but
> remains visible until replaced by another visual stimulus, so actual
> presentation duration is
>
> Stim2.OnsetTime - Stim1.OnsetTime
>
> and EP2.0.10.x Pro can now log those values for you
> (http://www.pstnet.com/support/kb.asp?TopicID=718 )!
>
>
> >3) The fact that Inline2 is executed at the same time as Inline1 is
> >particulary disturbing for me. Does that mean than Inline placed
> >after an object could be executed while this object is still on screen?
>
> Yes, and that is exactly what we want it to do in many, many cases
> (e.g., to handle multiple mouse actions while a visual stimulus
> remains on the display, or to prepare the next stimulus during the
> run of the current stimulus). If you really want your InLine to wait
> until the previous object completes its Duration, then set PreRelease
> of that object to 0.
>
> Hope that helps,
> -----
> David McFarlane
> E-Prime training
> online: http://psychology.msu.edu/Workshops_Courses/eprime.aspx
> Twitter: @EPrimeMaster (https://twitter.com/EPrimeMaster)
>
>
> >Thank you for any answer, I'm confused about this!
> >
> >Sylvain
> >
> >On Friday, September 10, 2010 3:46:03 PM UTC+2, David McFarlane wrote:
> >When you look at the Logging tab on the properties page of any
> >stimulus object, you will find a host of items available for
> >logging. Most of these are time audit data. But what do all these
> >items mean, and what are they good for? Chapter 3 of the E-Prime
> >User's Guide discusses time auditing to some degree, and the timing
> >diagram at Appendix E provides one way to see the relationships
> >between these items. As an alternative, here I try to set out, in
> >order, a brief description of these items.
> >
> >First let us distinguish between timing control *settings* and time
> >audit *measures*. The following items do not reflect any results
> >formed during the course of a stimulus but simply log the settings
> >provided by the user (e.g., you). You may choose to have any of
> >these logged just to keep a record of settings active during the
> experiment:
> >- Duration: To reiterate, this does *not* show the actual duration of
> > the stimulus, only the setting as provided by the user.
> >- PreRelease: Affects the TargetOffsetTime (see below).
> >- TimingMode: Event, Cumulative, or Custom, as set by the user (see
> > the online E-Basic Help).
> >- CustomOffsetTime: In Custom timing mode, overrides the
> > TargetOnsetTime (see the online E-Basic Help).
> >- CustomOnsetTime: In Custom timing mode, overrides the
> > TargetOffsetTime (see the online E-Basic Help).
> >
> >Now, the raw time audit measures, listed in the order in which events
> >occur during the execution of a stimulus object. These are all time
> >stamps in milliseconds from the start of the current program run:
> >- StartTime: Time at which E-Prime started executing the stimulus
> > object.
> >- TargetOnsetTime: Scheduled time at which presentation of stimulus was
> > to begin; set automatically from GetNextTargetOnsetTime (see online
> > E-Basic Help).
> >- OnsetTime: Time when E-Prime actually submitted the stimulus data for
> > presentation (e.g., proceeded to copy data to display memory or load
> > sound buffer). This may not coincide with when the stimulus actually
> > got presented, e.g., if data are submitted in the middle of a display
> > refresh cycle then they may not get presented until the next refresh.
> >- ActionTime: According to the online E-Basic Help, time at which
> > E-Prime completed the "critical action" of the stimulus. The
> > documentation remains somewhat vague about this -- perhaps "critical
> > action" means copying data to display memory, or loading a sound or
> > video buffer. In my tests, ActionTime never lags more than 1 ms
> > behind OnsetTime, so it serves practically the same purpose as
> > OnsetTime.
> >- TargetOffsetTime: Scheduled time at which offset actions (e.g.,
> > clean-up, ClearAfter, StopAfter) of stimulus object were to begin,
> > e.g., OnsetTime + Duration - PreRelease (Event timing mode), or
> > TargetOnsetTime + Duration - PreRelease (Cumulative timing mode).
> >- OffsetTime: Time when E-Prime actually began the offset actions of
> > the object. Actions may not take practical effect until next
> > vertical blank, or until presentation of next stimulus.
> >- FinishTime: Time when E-Prime exited from execution of the
> > stimulus object and proceeded to execute the next section of the
> > program (e.g., next stimulus object or inline code). Note that
> > *execution* of a stimulus *object* may end before *presentation* of
> > the *stimulus* ends; this is the point of PreRelease (as well as
> > happening as a matter of course with some stimuli such as some
> > sounds).
> >
> >Finally, a few composite time audit measures derived from the raw
> >measures above and provided for convenience:
> >- OnsetDelay = OnsetTime - TargetOnsetTime
> >- ActionDelay = ActionTime - OnsetTime
> >- OffsetDelay = OffsetTime - TargetOffsetTime
> >- DurationError = OffsetTime + PreRelease - OnsetTime - Duration
> >
> >Note:
> >- Time audit measures include the ActionTime that follows upon
> > OnsetTime, but no corresponding item to follow upon OffsetTime.
> >- No time audit item for time stamp of vertical blank, although many
> > stimuli do not take full effect until just after a vertical blank.
> >
> >-- David McFarlane, Professional Faultfinder
> >
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