How to avoid presenting targets consecutively

[ben robinson]

maybe you've already figured out your solution maybe not.  here's what i'd
do.

i would have a List1 with two procedures: Target and NonTarget.  set List1
to random.
* the Target procedure would have a List2 with two rows and one added
column, WavFile.  WavFile would be filled in with "[Wav]" to pull from a
column by that name in a nested list.  on one row you would nest the list
TargetWavs (unless there were only ever a single target wav, in which case
you wouldn't need to fool with a nested list), and on the other row you
would nest the list NonTargetWavs.  fill NonTargetWavs with all the
nontarget.wav filenames under a column named Wav.
* the NonTarget procedure would have a List3 with one added column, WavFile.
 again, if there's only a single nontarget.wav (apple.wav) you might just
enter that by hand in the column, WavFile.  otherwise, nest your
NonTargetWavs list.
adjust the weighting in List1 or in List3 to determine how many nontargets
are presented between each target presentation.

does that make sense?


On Fri, Jul 15, 2011 at 10:18 PM, Mark A <markbfm at gmail.com> wrote:

> Dear E-Prime group,
> I am fairly new to E-Prime, but thus far have found online discussions
> within the group, as well as PST instructions and examples that have
> allowed me to program everything required, with one exception. The
> experimental task is simple: A participant listens to a series of
> words and presses a button whenever a particular word is heard (i.e.,
> the target word, "apple" in the example below). The target word is
> presented 4 times.
>
> My problem is this: I wish to present a series of stimuli (.wav files)
> randomly, with the restriction that I do not want "Target" files to be
> presented consecutively. Rather, I want them to be separated by at
> least one distractor (or non-target).
>
> To illustrate, this is an excerpt from one of my lists:
>
> Weight  Nested  Procedure       Sound           Talker  Target  SoundDur
> 1                               MAppleTrial     m1apple.wav     m1
>      yes             422
> 1                               MAppleTrial     f4apple.wav     f4
>      yes             546
> 1                               MAppleTrial     m1apple.wav     m1
>      yes             422
> 1                               MAppleTrial     f4apple.wav     f4
>      yes             546
> 1                               MAppleTrial     m2bear.wav      m2
>      no              332
> 1                               MAppleTrial     f3bin.wav       f3
>      no              375
> 1                               MAppleTrial     m3cat.wav               m3
>              no              383
> 1                               MAppleTrial     f2chalk.wav     f2
>      no              586
> ..... and so forth (there are 4 targets and 23 distractors).
>
> Currently, I have the list set to "Random", however, this does not
> guarantee that the Target files (top 4 rows) will not occur
> consecutively. I think that the solution will involve a conditional
> statement (perhaps using In line) comparing whether the previous file
> presented was a target, but I am unsure how to implement this.
>
> An additional consideration is what to do if there are only 2 cycles
> left, and the two files left are both target files. If this is very
> hard to avoid, I am willing to live with this, as it is unlikely to
> occur very often. Any tips or links to helpful discussions on similar
> topics will be very much appreciated.
>
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