How to avoid presenting targets consecutively

[Micah]

Just as a general comment, and certainly not the best solution:

I generally do my stimulus randomizations outside of e-prime. It's
much easier to specific a pseudo-random or fully random sequence of
stimuli outside of e-prime (in excel for example) and to then import
it into one triallist that is sequentially sampled. This way you can
randomize the list while keeping a look out for exactly the kinds of
problem you mention.

Hope that helps,
Micah

Mark A 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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