User`s guide

E-Prime User’s Guide
Chapter 3: Critical Timing
Page 106
The Fixation and Probe objects use PreRelease to provide setup time so the Fixation stimulus
can flip to the Probe in a single refresh, and likewise, the Probe can flip to the Mask. The
durations should be set to be 10ms less than the calculated time based on the measured refresh
rate. The recorded refresh rate for the monitor was 60.16Hz, or 16.62ms. The Expected refresh
durations are calculated as follows (using the rule of thumb outline in section 3.4.2.1):
Object
Target
Duration
Target
Refresh Time
Duration
Specified
Timing
Mode
PreRelease Data Logging
Fixation
500 498.6 489 Event 100 Time Audit Only
Probe
100 99.7 90 Event 100 Standard
Mask
1500
(not critical)
1496.0 1500 Event 0 Time Audit Only
The duration of the Fixation and Probe are critical and are set to 10ms less than the target refresh
time to detect the vertical blanking signal. The timing mode of all of the events is set to Event
mode to ensure that the duration will be at least what was specified. The Mask duration, which is
not critical, is left at the nominal 1500. The PreRelease of 100ms releases that much time to the
setup of the next event. Note that if the PreRelease value is greater than or equal to the Duration
value, the object will PreRelease immediately after it has finished its critical action (e.g., displayed
the stimulus).
In this paradigm, the response processing of the Probe is critical. The probe is to have a
specified display duration of only 90ms, but the response processing is to continue for 2 seconds.
This is accomplished by using the extended response input option in the response processing
(see Time Limit field in Figure 17). Setting the Time Limit property for the input mask to 2000ms
and the End Action property to Terminate specifies that a response will be accepted for up to
2000ms post the onset time of the Probe object. When the subject response occurs, the
response will terminate whatever display is being presented (typically the Mask in this case).
Figure 17. Duration/Input specification of a response that extends past the
display time of the object.