[open] problem of the neverending loop

Comments

• sebastiaan

  November 2014 edited 7:25AM

  Hi,

  Let's say that you have the following structure:

  

  Here, the flicker_sequence presents one image, followed by a blank, followed by another image, followed by another blank. Each sketchpad is followed by keyboard_response that has a timeout of 500 ms. The result of this is that flicker_sequence presents images at a rate of 1 Hz.

  Now let's say that in the flicker_sequence has the following run-if statements:

  

  This means that once you press space, all subsequent items in the sequence will be skipped. So this allows you to stop flicker_sequence by pressing space.

  Of course, you want to repeat flicker_sequence until the participant actually presses space. You can do this by setting the repeat value in flicker_loop really high. And to make sure that flicker_loop also stops when space is pressed, you can set its break-if statement (under 'Show advanced options') to [response] = space.

  You see the logic here?

  One final thing to do is make sure that the variable response exists and doesn't have the value 'space' when flicker_loop starts. Because that will either give an error (if it doesn't exist) or cause the loop to not run at all (when response already has the value 'space'). To do so, simply add a simple inline_script before flicker_loop to reset the variable response, like so:

  exp.set('response', None)
  

  See? Easy peasy. You can download a simple example script here:

  • https://gist.github.com/smathot/e73bad4a37d424613c9f

  Cheers,
  Sebastiaan

  
  
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