Complex (for me) randomization

[David McFarlane]

Christophe,

Thanks for posting that.  I am glad that you were clever enough to 
cobble together a solution.  But if you take another look at the Slide 
exercise in the User's Guide, you might see that Slides offer a more 
general and flexible solution.  So here is another approach.

As before, in BlockList create an attribute called, say, BlockFace. 
Have your BlockProc do nothing more than call TrialList (do *not* have 
it present any Image or stimulus)   Then in your TrialList create an 
attribute called, say, TrialFace.  Now put a Slide into the TrialProc, 
let's call that StimSlide.  Add two SlideImage sub-objects in the 
appropriate places on the StimSlide.  In one SlideImage sub-object use 
"[BlockFace]" (without the quotes) for the File Name, in the other 
SlideImage use (you guessed it) "[TrialFace]".  And Bob's your uncle!

That may at first glance look like a more involved process, but as many 
others here may attest, if you take the time to learn how to use Slides 
you will find that it pays great dividends.

Regards,
-- David McFarlane, Professional Faultfinder


>> Ok..I finally managed to have the prog selecting one face and holding
>> it for the rest of the block trials. yeepee.
> 
>> You did not say how you did this, that would help us.
> 
> You are right, so...for beginners who get the same problem. I simply
> present the face picture with an imagedisplay object at the
> Blockprocess level, with a "0" in duration (position centered). Then I
> put my Triallist on its right, on the blockprocess line. From there I
> start a new Trialprocess, and put the second picture (bottom position)
> with Background set to "transparency". As the second picture is
> smaller than the face picture, they fit both nicely simultaneously on
> the screen. Now as I go through the block trials, only the second
> picture changes, not the face picture. When the block is over, a new
> face is selected, and the trials with the second pictures go on again,
> and so on for the other blocks.
> 
> I really thank you for your advice David.
> 
> Cheers,
> Christophe.

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