Sequential Timing for Sketchpad

Comments

• Fab

  September 2021

  Hi @opensesame,

  If what you'd like to do is to be able to set the duration of a sketchpad to vary it from trial to trial, the simplest solution is to include a column in your loop table that will contain the duration of your sketchpad and then call upon that variable when setting up your sketchpad.

  (I'm assuming that you're just referring to displaying sketchpads only, not displaying sketchpads and collecting responses. If you're after collecting a response to the sketchpad, you'd need a different solution).

  Set up the loop to include the duration as a variable. You can call this variable anything. Here I call it duration.

  

  Then set up the duration of your sketchpad to retrieve the value from that variable:

  

  You can download my example here (note that it is very basic; e.g., it does not contain a logger or take responses; the purpose is just to show you how to vary the duration of a sketchpad):

  Varying duration sketchpad.osexp

  Good luck!

  Fabrice.

  
• opensesame

  September 2021 edited September 2021

  Hello @Fab

  Thank you very much! It was very helpful. However, I have now run into a different issue:

  I have variables in the loop that I would like to present randomly, however, I intend for the duration of the sketchpad to follow a sequential order. Is there any way to do this? Perhaps an image would explain it better:

  

  
  

  The variable stimulus is ties to correct_response, and I would like them to be presented randomly

  I have tried to use the shuffle cue but cannot figure out how to get 2 columns to vary together

  Thank you!
• Fab

  September 2021

  Hi @opensesame,

  In order to achieve what you're after, you'll have to use some code (Python or Javascript if you're running your experiment in OS, and Javascript if you're aiming to run it with OSWeb).

  The general idea is to declare an array where the elements to be randomized are stored, shuffle it (if need be applying some conditions), and then output them to the loop as the task runs.

  Have a look at these examples to see how this works: https://forum.cogsci.nl/discussion/comment/23977#Comment_23977, https://forum.cogsci.nl/discussion/comment/24005#Comment_24005, https://forum.cogsci.nl/discussion/comment/23974#Comment_23974

  You'd also have to set the order property of the loop table to "sequential" so that duration of the sketchpad follows the order appearing in the table (the rest of the columns will be randomized using the code).

  Hope this helps,

  Fabrice.

  
• opensesame

  October 2021

  Hi @Fab

  Thank you very much! Will try it out.
• Fab

  October 2021

  Hi @opensesame,

  Here's an implementation of the solution I posted here: https://forum.cogsci.nl/discussion/comment/23974#Comment_23974

  I'm using Javascript code to (1) create an array containing the list of possible stimuli, (2) shuffle it, and (3) retrieve an element of the shuffled array to present it in the current trial.

  

  Here's the Javascript code used to create a function that shuffles the elements of an array (function shuffleArray(array)), create an array containing five stimuli (A, B, C, D, E) (let arr = ["A", "B", "C", "D", "E"];) and shuffles it (arr = shuffleArray(arr);). I also use code to ouput the shuffled array to the console, for monitoring.

  // defines function to shuffle the content of an array
  function shuffleArray(array) {
  let curId = array.length;
  // There remain elements to shuffle
  while (0 !== curId) {
  // Pick a remaining element
  let randId = Math.floor(Math.random() * curId);
  curId -= 1;
  // Swap it with the current element.
  let tmp = array[curId];
  array[curId] = array[randId];
  array[randId] = tmp;
  }
  return array;
  }
  // Usage of shuffle
  // arr contains the list of targets
  let arr = ["A", "B", "C", "D", "E"];
  arr = shuffleArray(arr);
  console.log("Shuffled order :"+arr);
  console.log ("arr[0]:"+arr[0]);
  // passing arr to vars.arr in order to be able to use it outside this inline_javascript object
  vars.arr=arr;
  // ressting trial number to 0
  vars.trial_counter=0;
  
  console.log ("vars.arr[0]:"+vars.arr[0]);
  

  With this method, note that the stimulus variable in the loop no longer needs to contain any information (the order method is set to sequential to make sure that the duration ispresented in the order specified in the loop table)...

  

  ... for it will be populated on the fly using the code contained in the retrieves_trial_info:

  // increment trial counter
  vars.trial_counter=vars.trial_counter+1
  
  // retrieves stimulus from vars.arr based on inblock trial counter -1 (because array goes from 0 to the array's length)
  vars.stimulus=vars.arr[vars.trial_counter-1]
  console.log("Trial number: "+vars.trial_counter)
  console.log("Duration: "+vars.duration+", stimulus:"+vars.stimulus)
  

  The method could be applied to other variables if you need to randomize several variables independently.

  Good luck,

  Fabrice.

  Modified example:

  Varying duration sketchpad.osexp