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
- TargetOnsetTime: Scheduled time at which presentation of stimulus was
to begin; set automatically from GetNextTargetOnsetTime (see online
- 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
- 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
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
- 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
Anyway, I should have closed with a list of references, so here it is:
- E-Prime User's Guide, Chapter 3 & Appendix E.
- E-Prime Reference Guide, section 188.8.131.52 Logging Tab.
- E-Basic online help, topic "Time Audit".
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