Newbie needing randomisation help!

Comments

• sebastiaan

  March 2017

  Hi,

  Let's start with points 1 and 2. An attentional-blink experiment is tricky to implement, and the best way is to use a bit of scripting. Here's an example of how you can do approximately what you want: It shows a stream of 10 letters, with a target ('X') and a cat probe ('C').

  This should be in the prepare phase:

  import random
  
  # We have eight distractors, one target, and a cat probe
  rsvp = list('abcdefgh')
  target = 'X'
  cat = 'C'
  
  # Randomly shuffle the rsvp stream, then randomly select
  # a target index (= position in the stream) and cat index
  # (two positions after the target). Then we insert the
  # target and the cat into the rsvp stream at the correct
  # positions.
  random.shuffle(rsvp)
  target_index = random.randint(0, 7)
  cat_index = target_index + 2
  rsvp.insert(cat_index, cat)
  rsvp.insert(target_index, target)
  
  # Now we create a list of canvas objects. We do this first
  # so that we have no preparation time when showing the canvas
  # objects later.
  canvas_list = []
  for stim in rsvp:
      stim_canvas = canvas()
      stim_canvas.text(stim)
      canvas_list.append(stim_canvas)
  

  And this in the run phase:

  # And now we show all canvas objects with a 90 ms
  # delay between them!
  for stim_canvas in canvas_list:
      stim_canvas.show()
      clock.sleep(90)
  

  Of course, you'll want to change this so that it shows images, rather than letters. And maybe a blank in between the images, etc. But first try that yourself as an exercise. If you follow the beginner and intermediate tutorials, you should get a long way!

  Cheers,
  Sebastiaan

  
  
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• jennzy11

  March 2017 edited March 2017

  Thanks Sebastiaan, I had found this in the tutorials but couldn't figure out how to import my image files into it as the list refers to letters. I have now made my main sequence using 10 different variables to randomise the sketchpads (a very long-winded way but it made more sense to me than the code!). However, I still need to randomise the widget response page. I currently have this code in place and it works perfectly:

  set timeout infinite
  set spacing 25
  set rows "1;1;1;1"
  set question "Select the black and white animal you saw. Or select 'don't know'"
  set options "draw image center=1 file=c_bird.jpg scale=1 show_if=always"
  set only_render no
  set margins "50;100;50;100"
  set form_var response
  set form_title "Form title"
  set description "A simple multiple choice item"
  set cols "1;1"
  set button_text Ok
  set allow_multiple no
  set advance_immediately yes
  set theme gray
  widget 0 0 2 1 label text="Target selection"
  widget 0 1 2 1 label center=no text="Select which black and white animal you saw or if you don't know select 'don't know' "
  widget 0 2 1 1 image_button path="bw[T1].jpg"
  widget 1 2 1 1 image_button path="bw_[picture3].jpg"
  widget 0 3 1 1 image_button path="bw_[picture2].jpg"
  widget 1 3 1 1 button text="Don't know"

  How can I adapt this code so that it randomises the order my widget buttons appear on the screen? At the moment the right answer is always the first button [T1].

  Thanks,
  Jenny