scoring a nonresponse as a correct answer

[David McFarlane]

Jim,

First, your earlier designed used what I call "multiple correct 
response targets".  By way of background, if you search this Group 
using terms like that then you will find where we have discussed 
several approaches to that.

Second, I wonder if something else is going on in your program?  I 
myself have used a blank [Correct] to score the accuracy of 
no-response trials (where the absence of a response is correct and 
any other response is incorrect) and that worked fine for me.  It 
should just work for you.

Third, you might want to study Chapter 3 further to better understand 
the intricacies of PreRelease.  Sadly, PST does not do a very good 
job of explaining it, and in fact the whole PreRelease mechanism 
provides much more granularity than users need or want (should be 
just on or off -- whenever I use PreRelease I just set it to some 
arbitrarily large value, often larger than the Duration, with no ill 
effects).  For instance, if you do not use the .ACC within the trial 
itself (only to log it) and know the response will come before the 
onset of the final object in trial Procedure, then you can safely use 
PreRelease with abandon and then use inline code after the final 
object to score the .ACC if needed.

Fourth, whenever I teach E-Prime for fMRI, I first briefly explain 
the difference between Event and Cumulative timing.  Then I just lay 
down the law and tell students, for fMRI, just make things easy and 
set *every* object to Cumulative timing!!  Yes, I know that is 
excessive, but I have yet to find a case where Cumulative timing 
creates a problem, whereas Event timing is known to create problems 
in several contexts.  If it were up to me I would just make 
Cumulative the default and then only allow users to choose Event mode 
if they think it really applies to their study (back when I wrote 
everything in C I did everything in what E-Prime calls "Cumulative" 
timing mode, it just seemed cleaner and took no real programming effort).

-- David McFarlane, Professional Faultfinder


At 2/22/2010 11:17 AM Monday, you wrote:
>i think you'll need to use an inline to do this, but i also think 
>you can mostly avoid the complications introduced by using the prerelease.
>here's what i would do:
>
>put your inline after the 1000 ms blank screen, knowing that the 
>inline code may be read as early as 900 ms into the blank screen's 
>duration (and only 1150 ms after onset of your letter stimulus).
>the script in the inline would be something like this:
>Do
>Loop Until (Clock.Read - LetterStimulus.OnsetTime) < (1250 - 
>Display.RefreshDurationStats.Mean)
>If LetterStimulus.RESP = "" And c.GetAttrib("Stim") = "X" Then 
>LetterStimulus.ACC = 1
>
>that Do...Loop will loop continuously until there is less than a 
>single screen refresh's worth of milliseconds remaining in the 
>LetterStimulus's response window, at which point the script will 
>kick out of the Do...Loop, check to see if there was no response, 
>and if no response and if 'X' then assign an accuracy of '1' to the 
>LetterStimulus object.
>
>how's that?
>
>ben
>
>On Mon, Feb 22, 2010 at 11:01 AM, Jim 
><<mailto:jjprisciandaro at gmail.com>jjprisciandaro at gmail.com> wrote:
>Hello forum,
>
>I sent this question to e-prime support last week; unfortunately, they
>are experiencing high volume and have been taking a long time to get
>back to my requests. They are time sensitive, so I was hoping the
>forum might have some ideas.
>
>I'm working with an e-prime experiment where participants are asked to
>press a button ("7") whenever they see a letter except for "X" (at
>which point they are asked to withold a response). I have a column in
>my task list "CorrectAnswerL" which states "7" for any letter (another
>column in the task list) other than X; CorrectAnswerL is blank for
>trials with "X"s. In the procedure associated with that list, the
>stimulus "LetterPresentation" has [CorrectAnswerL] listed in the
>"Correct" blank in the "Duration/Input" tab. When I run the task,
>nonresponses are not scored as correct for X trials (that is,
>LetterPresentation.ACC = 0).
>
>I previously had the task running with an inline script following the
>stimulus and a blank pane "ISI" which stated:
>
>If LetterPresentation.RESP = c.GetAttrib ("CorrectAnswerR") OR
>LetterPresentation.RESP = c.GetAttrib ("CorrectAnswerL") Then
>LetterPresentation.ACC = 1
>End If
>
>At this time there were two correct responses which is why there is an
>additional "correctanswer" attribute. This is no longer the case, and
>I want to remove the inline code. However, when I was using this code,
>nonresponses were scored as correct for X trials. Please let me know
>how I can have nonresponses scored as correct for X trials without
>using inline code.
>
>As an aside, I removed the inline code because I am concerned that it
>will be executed too early. Each trial consists of the presentation of
>a letter (250ms), and subsequently a blank screen (1000ms)- both
>objects have a 100ms prerelease. Once the letter is presented,
>participants have until the end of the blank screen (1250ms later) to
>make a response. I prevously had the inline script following the blank
>screen object ("ISI"). I've been reading the critical timing chapter
>of the eprime manual which made me concerned that if participants made
>a response between 1150 and 1250ms their response will not be scored
>with inline code because of the 100ms prerelease on the blank screen.
>A complicating factor, is that I can't change the timing of the task
>whatsoever, it has an associated fMRI program that it must be tightly
>timed with.
>
>Thanks,
>Jim

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