Re-visiting Pseudo-Randomization

[Ben Robinson]

one way to do this, without any scripting, would be to have several lists.
1st list: one item - not an X
2nd list: 7 items, including your X, selected randomly
3rd list: 1 item - not an X
 
each of the 3 lists would have the same nested list, call it FontsList, with 4 items in it (32, 72, and two other font sizes).  these 4 font sizes would be in a column called FontSize, and items from FontsList would be randomly selected.
 
then, within your procedure, the TextDisplay item presenting your stimuli would reference the column [FontSize] such that each presented stimulus would pull a fontsize at random from your FontsList.
 
make sense?
 
SessionProc
   List1 (1 item, not an X, with FontsList nested)
      PresentationProc
   List2 (7 items, including X, with FontsList nested)
      PresentationProc
   List3 (1 item, not an X, with FontsList nested)
      PresentationProc


 
ben robinson

>>> "Mark Chan" <mr.mark.chan at gmail.com> 10/6/2006 12:56 AM >>>

'm trying to design a study with Pseudo-Random presentation of stimuli.

Basically this is what i'm looking at:

I'll be presenting 9 different objects in 25 blocks
There is a target object, which we will call "X".I need "X" to appear once within each block
"X" cannot re-appear back to back.
  i.e. end of block 1, we have... stimuli, stimuli, TARGET, start of block 2 TARGET, stimuli, stimuli...this cannot occurIt would be preferable if there were at least 3 stimuli between TARGET presentation. We do not wish to have repeats of stimuli and target within each block. 
Also, i was wondering if you could have the font sizes change randomly (4 different sizes) between stimuli. Say first stimuli, font = 32, next stimui = 72, etc.

Any ideas?

Thanks! 

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