[solved] nested A.B.B.A structure

Comments

• sebastiaan

  February 2014 edited 10:01AM

  Hi Dror,

  I want the exp to "remember" which trail I used and to run every trail and all off the trails once

  This is an interesting question. What I would do first is add a column with a unique identifier for each trial. For example, a variable named trialid that identifies the block (A or B) and the trial number (instead of digit you would have your own conditions, of course):

  

  The next step would be to keep track of which trial is presented, by adding the trialid to a list at the end of each trial_sequence. You can do this with a simple inline_script (in the run phase):

  # At the end of each trial (run phase)
  self.experiment.trials_done.append(self.get('trialid'))
  

  Of course, you also need to initialize self.experiment.trials_done at the start of the experiment, again with a simple inline_script:

  # At the start of the experiment (prepare phase)
  self.experiment.trials_done = []
  

  Now you can use a run-if statement in your trial_sequence to skip all trials that have already been presented, by adding the following run-if statement to all items the trial_sequence". (Note that this a Python-style run-if statement).

  =self.get('trialid') not in self.experiment.trials_done
  

  Now we're getting somewhere!

  Of course, the first time that the block_loop is executed, we want to present only half the trials (60 of 120 in your case), so we set 'repeat' to 0.5. However, the second time that the block_loop is executed we want to present all trials, and use the run-if statement described above to skip the trials that were already presented (so effectively presenting the other half of the trials). We can do this by changing the repeat setting of the block_loop programmatically, after the block_loop has been executed for the first time:

  # At the end of the the block_sequence (run phase)
  exp.items['block_loop'].repeat = 1
  

  This is basically it. Now you have a block_loop that runs 50% of the trials on the first execution, and the other 50% on the second execution! It may seem like a lot to take in, but if you first implement the steps above in a simple dummy experiment, you will see the logic of it.

  I want counter balance the tasks between subj (ABBA, BAAB)

  For detailed information about counterbalancing, see this page:

  • http://osdoc.cogsci.nl/miscellaneous/counterbalancing/

  Cheers!
  Sebastiaan

  
  
  Check out SigmundAI.eu for our OpenSesame AI assistant!
  
• drorgarbi

  February 2014 edited 10:01AM

  hi
  I find your solution very flexible and much simpler then what I used
  thanx - I will use it!
  but one thing I did not understood, how do you control which block type a\b will be presented? are they in a same list or different one?
  Dror
• sebastiaan

  February 2014 edited 10:01AM

  Hi Dror,

  I would treat blocks A and B as different block loops (block_loop_A and block_loop_B), so your experiment would go like this for some participants:

  block_loop_A
  block_loop_B
  block_loop_B
  block_loop_A
  

  And like this for others:

  block_loop_B
  block_loop_A
  block_loop_A
  block_loop_B
  

  So you basically perform the trick I described above separately for block_loop_A and block_loop_B.

  Cheers,
  Sebastiaan

  
  
  Check out SigmundAI.eu for our OpenSesame AI assistant!