scoring a nonresponse as a correct answer

[ben robinson]

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 <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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