How to use .txt file to assign order to stimuli presentation?

Comments

• eduard

  January 2019

  Hi,

  I am not sure whether I entirely understand what you want to accomplish. So you have eight different words in total, and present them in a random order for 700 times in total. Is this correct? Or what information do you get from the template?

  Generally, if you want to control stuff happening across participants, you can use the variable var.subject_nr. So here a little example how to go about that:

  # this code assigns three different orders of stimuli over all subjects
  # the '%' is the modulo operator and returns the rest of a division. e.g. 1%3 returns 1, 2%3 returns 2, and 3%3 returns 0
  
  if var.subject_nr%3 == 0:
      stim_order == ['red','blue','green']
  elif var.subject_nr%3 == 1: 
      stim_order == ['red','green','blue']
  elif var.subject_nr%3 == 2: 
      stim_order == ['blue','green','red']
  
  # depending on the participant number another order of items is being used. 
  

  Btw. If you are new to Python, I can only recommend that you spend some extra time now to learn Python before you proceed programming experiments. Even if it slows you down now a little, you will see that you'll be much quicker and better solving problems in the future. Here a link to some resources.

  Eduard

  
• peapodpeapod

  January 2019 edited January 2019

  Hi Eduard,

  Thank you so much for taking the time to respond. I will definitely have a look at the Python resources.

  The .txt template is the order in which the stimuli should be presented in the training phase. It provides a fixed order for the presentation of 700 trials. So I have eight different words, that should be presented in the fixed order as defined by the .txt file. Here is a segment of the .txt file: So e.g. [a0] will always = apple for participant 1, but banana for participant 2. [b1] = watermelon for participant 1, but kumquat for participant 2. I hope this clarifies things a little.

  Is there a way for me to import/load the .txtfile to fix the order of presentation, but randomise the stimuli for each participant? Additionally, would I be able to carry over the values of [a0], [a1], [b0] etc, for each participant into the testing phase (e.g. have [a0] be banana for participant 1 in both the training phase and the testing phase) ?
• eduard

  January 2019

  I think probably the easiest would be to define the mapping in the beginning of the experiment, and then replace the items. For example:

  import random
  # load the text file
  # as I dont have the text file I just create an example list
  example_txt = ["[a0]","[a1]","[b0]"]*20
  random.shuffle(example_txt)
  
  # define how the txt content maps on words, depending on participant number
  if var.subject_nr%3 == 0:
      mapping = {'[a0]':'apple','[a1]':'banana', '[b0]':'peach'}
  elif var.subject_nr%3 == 1:
      mapping = {'[a1]':'apple','[a0]':'banana', '[b0]':'peach'}
  
  # make a new list and add one by one the mapped labels to it
  replaced_list = []
  for item in example_txt:
       replaced_list.append(mapping[item])
  

  Hope this helps.
  Eduard