[solved] Adding random events throughout a block

Comments

• Edwin

  January 2015 edited January 2015

  Hi Daniel,

  I would advise against using the parallel plug-in, unless it is absolutely necessary. Assuming you are using an inline_script to present the aversive stimulus, your trial sequence will look something like this:

  - sketchpad (fixation)
  - sketchpad (stimulus)
  - keyboard_response
  - inline_script (for noise/shock)
  

  Alternatively, you could make it look like this:

  - inline_script (determine whether shock happens)
  - inline_script (noise/shock)
  - sketchpad (fixation)
  - inline_script (noise/shock)
  - sketchpad (stimulus)
  - inline_script (noise/shock)
  - keyboard_response
  - inline_script (noise/shock)
  

  Where the first inline_script determines whether there will be a shock this trial. I will assume you have already implemented this, using some probability of a shock occurring, like below (although the 0.2 is probably a variable in your case).

  import random
  
  # shocks occur in 20% of trials
  exp.shock_this_trial = random.random() < 0.2
  
  # shock has not occurred yet
  exp.shocked_this_trial = False
  

  Each further inline_script starts with the following snippet:

  # check if the current trial is a shock trial,
  # and no shock has occurred yet
  if exp.shock_this_trial and not exp.shocked_this_trial:
  
      # 25% chance of the shock occurring in this inline_script
      # (100% divided by the number of times this
      # inline_script is repeated in the trial)
      exp.shocked_this_trial = random.random() < 0.25
  
      # aversive stimulus
      if exp.shocked_this_trial:
  
          # SHOCK CODE HERE
  

  Of course, this is a bit of a crude way to do it. However, it's quick-and-dirty, and nicely random and thus very unpredictable (even for the experimenter!).

  Hope this gives you some inspiration!
• DPrec

  January 2015 edited 8:19AM

  Hey Edwin,

  That will do nicely, good idea! I'II will have to break down my trial inlines to make it work (I usually have the entire trial sequence scripted in a single inline), but I agree, by implementing it like you recommended definitely makes it quite unpredictable.

  Thanks a lot for your input,

  Daniel
• Edwin

  January 2015 edited January 2015

  No worries! Hope you can make it work!

  BTW: If you're already scripting all the way, I've implemented something similar in the past in Python (using PyGaze, but using PyGame or PsychoPy directly would also do the trick). The idea there was simple: the main Thread was used to display pictures, while one sub-Thread was used to play sounds and another to log keypresses (the onsets of which were compared afterwards). The point is that, if you are already going through the effort of coding everything in OpenSesame, you might try to code an experiment from scratch in Python with only a bit more effort.

  Of course, using OpenSesame is still quicker for more straightforward designs. But if you want to do things in parallel, Python provides excellent tools for multithreading (and even proper parallel processing, although the differences between multithreading and parallel processing usually don't matter a lot for experiments).

  Either way: good luck!

  Edwin

  PS: Marking this one as solved, but please don't hesitate to post here again (and mark the thread open) if further questions arise!