summary for wav file RTs

[Carol Anne Miller]

Thanks to everyone who responded to my question about measuring RT from a
point within a wav file.  Several practical suggestions were made, and I
will give them a try.  Below are my question and the responses, for those
who are interested.
Carol
I am collecting response times to sound files.  In the experiment I am
working on, the subjects' task is to listen to a sentence and press one
button if it is grammatically correct, and another button if it is
incorrect (I'm using the PST Serial Response Box).  I have this experiment
working all right, but I would like to refine it:  I would like to measure
the RT from the onset of a crucial word in the sentence, rather than from
the onset of the sound file.  Is there a way to either a) place a marker in
the sound file that will tell Eprime to start measuring RT?  or b) tell
Eprime to start measuring RT at a certain point , i.e., file onset + xxx
ms?  The crucial point is different for each sentence.

#1
Is making each word a separate object/event out of the question? Otherwise
this seems like to most straight forward attempt.
Good Luck
Dan

#2
Here's a way that would probably work. In a list
object, have one attribute that contains the name of
the sound file for each trial, and another that
contains the offset of the crucial time in
milliseconds for that file. Then set your sound
object to have duration equal to the crucial time,
making sure that the sound object is configured to
continue playing the sound after the sound object
terminates. Then have a blank screen (i.e. a blank
text object) that follows the sound object, with
user input enabled.


Tom Johnstone, Ph.D.
Keck Laboratory for Functional Brain Imaging and
Behavior
Waisman Center
University of Wisconsin-Madison

#3  (David Fencsik and Tony Zuccolotto came up with essentially the same
solution)
I assume you have a list object that specifies which sound file to use
on each trial. If this is the case, then you can add a column to the
list object that specifies the time from the onset of the sound to the
onset of the crucial word. After the response is collected, you could
create a script that looks up the time and subtracts it from the RT.
Or, to be safe, you could create a new attribute that stores the RT
minus the time delay.

David

***********
There is no way currently in E-Prime to automatically adjust an RT based
on the offset of a word in the file.

To do this you would probably have to list the word offsets as an
attribute and then insert some script at the end of the trial to adjust
the RT, e.g.

         If Stimulus.RT > c.GetAttrib( "WordOffset") Then
                 Stimulus.RT = Stimulus.RT - c.GetAttrib("WordOffset")
         Else
                 ' Responded before the word was presented
                 Stimulus.RT = 0
         End If

Hope that helps.

Tony

*** DISCLAIMER: ALL VIEWS EXPRESSED ARE MY OWN AND DO NOT NECESSARILY
REFLECT THOSE OF PSYCHOLOGY SOFTWARE TOOLS ***




++++++++++++++++++++++++++++
Carol Miller, Ph.D.
Dept. of Communication Sciences & Disorders
Penn State University
115-B Moore Building
(814) 865-6213
cam47 at psu.edu
++++++++++++++++++++++++++++
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