[solved] vary a sketchpad duration according to the previous response time

Comments

• lvanderlinden

  July 2013 edited 1:17PM

  Hi,

  The 'duration' box in a sketchpad item only takes fixed variables. As a solution, you can calculate the desired duration in an inline_script item placed immediately before your sketchpad item. Next, you can use the square-bracket method (e.g. [my_duration]) in the duration box.

  You can calculate the desired duration by placing something like the following code in the Prepare phase tab of your inline script:

  # Set the maximum:
  max = 2000.
  
  # Determine the RT on the previous trial by 
  # using the experiment function self.get().
  
  # See: http://osdoc.cogsci.nl/python-inline-code/experiment-functions/#experiment.get
  dur = max - self.get("response_time")
  
  # Set the resulting duration so that the variable becomes
  # available in the interface (i.e. in your case a sketchpad item)
  # as well:
  
  # See: http://osdoc.cogsci.nl/python-inline-code/experiment-functions/#experiment.set
  exp.set("my_duration", dur)
  

  This code will work on all trials except the first trial of your experiment, because at that time the variable 'response_time' does not have a value yet. Therefore, you should also append a second inline_script item to the very beginning of your experiment, and give 'response_time' a starting value. You can do this by placing something like this in the Prepare phase tab:

  # Give the variable 'response_time' a starting
  # value such that it already exists for the very first 
  # trial (otherwise OpenSesame will give an error
  # saying that the variable 'response_time' does
  # not exist):
  
  exp.set("response_time", 0)
  

  Your experimental overview should look something like this:

  

  Does that make sense?

  Best wishes,

  Lotje

  Did you like my answer? Feel free to
• perrein

  July 2013 edited 1:17PM

  Great! It perfectly works. Thanks a lot.
• perrein

  July 2013 edited 1:17PM

  Hi,

  I just realized that with your help I collect the rt of the previous trial, but I would like to collect the rt of the current one.
  I tried several things but coulnd not find any solution for the moment. Would you have any idea, please?
  Best,
• perrein

  July 2013 edited 1:17PM

  I found the beginning of a solution.
  When I use your code in the "Run Phase" and I display response_time in the debug window, my_duration displays the correct current RT.

  My last remaining problem is that, now, I cannot access to the variable "my_duration" on another sketchpad (placed after the inline of course). I tried to declare it as "global" but that does not work.
• perrein

  July 2013 edited 1:17PM

  My problem was not an access problem. I forgot to give "my_duration" a starting value as you mentioned...
  Thanks again for your help!
• sebastiaan

  July 2013 edited 1:17PM

  Hi,

  I'm not sure whether you already worked it out, but here's a small tip anyway. You can 'pad' the remaining time after a response with this simple script:

  total_time = 5000 # The response time + the padding time
  padding_time = total_time - self.get('response_time')
  if padding_time > 0:
      self.sleep(padding_time)
  

  So let's say that you have sketchpad1, followed by a keyboard_response, and then you want to 'pad' the remaining 5 seconds while showing sketchpad2. You can do this with the following sequence:

  • sketchpad1 (duration = 0)
  • keyboard_response
  • sketchpad2 (duration = 0)
  • inline_script (with the code show above)

  Does that make sense? So you don't use the 'duration' parameter of the sketchpad, but simply use an inline_script item.

  Hope this helps!

  Cheers,
  Sebastiaan

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

  July 2013 edited 1:17PM

  thank you very much, it perfectly works as I wanted with this strategy.