Stop Signal ISI Randomization?

[Tony Andrews]

Dear Zach



This is exactly the sort of thing that nested lists are for.



Your TrialList should contain (in addition to your other attributes) an
attribute for the ISI. This attribute should contain the name of an
attribute in a nested listed e.g. [IstimI] and the name of the nested list
should be placed in the Nested column.



There is a sample experiment that comes with E-Prime that demonstrates this.
It also uses the 'colon' notation, which IMO complicates things and for your
purposes you can ignore that part.



I think you'll also find more eloquent explanations on the archives of this
mailing list and in the user forums.



Regards,



Tony.


On Wed, Nov 12, 2008 at 7:26 PM, Zach <zachary.d.cohen at gmail.com> wrote:

>
> Hello All,
>        This is my first time posting but as a new user of EPrime,
> reading this list serve has been immensely helpful over the past month
> and for that I thank you.
>
> The problem I am currently grappling with is one of randomization. I
> have a stop signal program that randomly (w/o replacement) presents
> the user with 4 stimuli (goleft, goright, stopleft, and stopright),
> with each stimulus presentation separated by inter-stimulus-interval
> (blank screen). I have these 4 stimuli as separate procedures under a
> List that weights each of the four differently (more go trials than
> stop). In between each stimuli presentation I am attempting to
> randomly (w/o replacement) select the ISI time from a weighted list
> with five possible times (500ms, 750ms, etc).
>
> My problem is that I cannot seem to get EPrime to randomly select both
> without replacement in series. I need the program to run through
> exactly the same amount of each stimulus (goL, goR etc) and the same
> distribution of ISIs (500ms, 750ms etc) while randomly selecting and
> pair both w/o replacement. I can get it to do one but not the other,
> and was wondering if anyone knew a way to effectively place two lists
> in a row, so that the program would choose randomly from one list and
> then the other. Alternatively, would there be a way to have a list of
> ISItimes that could be randomly accessed (w/o replacement) inside the
> GoL GoR StopL StopR programs.
>
> For example, the program would function as follows:
> (P) TrialProcedure
>     - (L) TrialList (with weighted GoL GoR etc.)
>            - (P) GoL_procedure
>                - (Slide) Fix
>                        - (Slide) ArrowLeft
>                        - (Slide) ISI   [and here the ISI time could
> randomly access this magical list and select the time interval]
>            - (P) GoR_procedure
> END
>
> I hope that my question isn't too long and that I explained everything
> adequately. If anyone has any ideas I would greatly appreciate your
> help.
> Sincere Thanks,
>         -Zach Cohen
> >
>

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