User`s guide

E-Prime User’s Guide
Chapter 2: Using E-Studio
Page 29
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Verify that the conditions, stimuli, and correct responses (i.e., independent variables) are logged
as expected.
2.3.8.4 Find the dependent variables and verify they are set
reasonably
Verify the logging of the dependent measures. The RESP property is the actual response
entered, and is logged as NULL for a non-response. The CRESP property is the correct answer,
which varies per trial, and ACC is the accuracy of the response (RESP) in relation to the correct
answer (CRESP). ACC is set to “1” for correct answers and to “0” for incorrect answers or
omissions. RT, of course, is the reaction time for the response measured from the onset of the
object collecting the input. Verify that the values logged for the dependent variables are as
expected for the test trials (e.g., RT values are appropriate for short and long response times, “0”
for omissions, etc.).
2.3.8.5 Check timing duration accuracy on fixed length
displays
Verifying timing precision is a critical function. Issues related to timing are detailed in Chapter 3 -
Critical Timing in the User's Guide. Here we will only provide brief accounts of timing issues. In
general, in E-Prime, the time from stimulus to response is accurately recorded. The duration from
stimulus to stimulus may be somewhat longer than specified in the Duration field. This is
because the display is written at the time of the vertical retrace (when the video monitor output of
the image goes to the top line of the display). The time from one display to the next is equal to
the duration of the first display plus the time until the next vertical blank interval. In this
experiment, the Fixation had a duration of 1000ms. The actual time from the Fixation to the
stimulus would be equal to the time of the duration of the Fixation plus the OnsetDelay of the
Probe object. It is important to verify this duration in order to accurately report the measured
fixation duration. In our experiment, use E-DataAid to examine the Probe.OnsetDelay variable
(should range from 0 to 17 milliseconds). To illustrate, if the Probe.OnsetDelay is 12, then the
fixation duration would be the duration (1000ms) plus 12ms, or 1012ms in length (see Chapter 3
– Critical Timing).