User`s guide

E-Prime User’s Guide

Chapter 3: Critical Timing

Page 112

Figure 20. Timing Paradigm 4 with ellipse over

critical events including stimulus selection and the

procedure.

To present the loop on a fixed schedule, we remove all subject input termination from the trial

loop

. For example, the trial instructions are now presented once at the beginning of the

experiment, rather than in the trial loop. The subject does not need to be presented with the trial

instructions during each cycle, and removing the instructions from the trial procedure removes

any time variability due to how long the subject looks at the instructions. The End Action for the

response to the Probe (i.e., on the Duration/Input Tab) is changed to (none) rather than

Terminate. This results in the mask being presented for 1900ms, independent of when or if the

subject responds. The timing mode for all of the events in the critical loop is set to Cumulative so

that the total timing would be set correctly. In addition, a GetReady display was added to begin

the critical timing loop, and a PreRelease is specified to allow the first presentation to start at a

fixed point in time. The critical parameter settings for the objects are shown in the table below.

Object Target

Duration

Timing Mode PreRelease Data Logging Onset Sync

GetReady 100 (start) Event 100 Time Audit Only Vertical blank

Fixation 500 Cumulative 200 Time Audit only Vertical blank

Probe 100 Cumulative 100 Standard Vertical blank

Mask 1900 Cumulative 200 Time Audit Only Vertical blank

Feedback 1000 Cumulative 200 Time Audit Only Vertical blank

In this case, we are setting up a repeating loop. The GetReady object is set to Event timing

mode and begins the loop with a 100ms second delay and PreRelease to allow for the

preparation of the first stimulus. The other events run in Cumulative timing mode, maintaining

timing accuracy with no cumulative drift relative to the end of the GetReady event. The time for

the first Fixation relative to the end of the GetReady should be at 0ms, the second at 3500, the

Alternatively one could compensate for the subject modification of timing by delaying the start of the next

trial. For example, you could have the computer clear the display on subject response but then increase the

inter-trial interval to compensate for the time of the event. This can be done with a single line of Inline script

inserted at the end of the trial (e.g., SetNextTargetOnsetTime Probe.OnsetTime + 3000), but will not be

described in this example.