Dear Shane and Chris,


The problem is with these lines :

   corr1 <- Nth(des,1)==0

   corr2 <- Nth(des,2)==0



Strangely, the variable saved will be according to the previous test (last 
trial). Printing corr1 for each trial before and after the if made it clear. We 
don’t see this pattern for the hits as this test is overwritten during the 
“if”. Another peculiar behavior is that sometimes, corr on the very first trial 
is 0. As it isn’t systematic, I have a really hard time figuring what happens. 
I have been using such y <- x==0 in other scripts and it seems to work as 
expected for me.



Shane, this is highly disturbing. If statements like y <- x==0 are not always 
giving the same behavior, then it’s important to know we shouldn’t use them 
anymore. Or at least know in which circumstances it happens.



Best regards,

Laurent Schüpbach





From: Shane Mueller<mailto:[email protected]>
Sent: Friday, March 25, 2016 04:26
To: Christopher Higginson<mailto:[email protected]>; 
[email protected]<mailto:[email protected]>
Subject: Re: [Pebl-list] n-Back



Chris,
I believe that somebody reported that to me recently, so I don't think
you are incorrect.  I haven't verified this yet, but it if it isn't
correct, then columns may be mislabeled.


Here is the logic--maybe you have a fix?  the variable corr1 (and
corr2) starts out with a default value that should be correct if no
response were made:

   corr1 <- Nth(des,1)==0
   corr2 <- Nth(des,2)==0


It sounds like this

Then there are two blocks of code that record whether each of two
possible responses are correct.  The second one is this, which would be
the code that gets tested when the second response times out after the
first response is complete:

     if(resp2 == "<lshift>")
       {
          Show(respLeft)
          corr1 <- Nth(des,1)
       }elseif(resp2=="<rshift>")
       {
          Show(respRight)
          corr2 <- Nth(des,2)
       }

Here, neither of these would run if there were a timeout, and so corr1
would default to the original value above. So maybe the original
default score is backward?  I think in des, it is marked a 0 if there
is no n-back match and 1 if there is, so if no response is made, it
should be marked as correct in that case; so I'm a bit puzzled what the
happening.  If you can send me an example data file and tell me what
the incorrect coding is, that would be helpful.

Shane

On Tue, 2016-03-22 at 15:36 +0000, Christopher Higginson wrote:
> Dear PEBL Project,
> I'm in the process of revising the n-Back task from the battery to
> better meet my needs. I will certainly pass along my edited version
> of the task when it is complete. I'm concerned about a potential
> error in the data file that is created. The column "corr1" (which
> appears to indicate whether the response is correct or not) seems to
> generate a score of "0" when a correct "timeout" (i.e., no response)
> response is made immediately after a "lshift" response. Has anyone
> else noticed this or am I missing something? Any assistance would be
> much appreciated!
> Chris
>
>
>
> Christopher I. Higginson, Ph.D.
> Associate Professor
> Department of Psychology
> Loyola University Maryland
> 4501 North Charles Street
> Baltimore, MD 21210
> 410-617-2461
>
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