function call as stimulus

[idoba2030]

Hey everyone,
Thanks for developing jspsych, I really enjoy working with it.

I need your help in the following matter.
I used the stimulus parameter as a function call that randomly picks images and locations to show on the memory array of the trial. I want to use the output of this function as I need it to then create the target array of the trial which draws upon those images and locations. I wasn't able to get access to the values generated by the random assignment to the stimulus parameter, as every time I call it generates new values.

    var memory_array = function (condition) {
        number_of_images = parseInt(condition[0])
        locations = get_locations(location_names, number_of_images)
        squares_array = get_squares(change_detection_images, number_of_images)
        var squares = '';
        for (index = 0; index < number_of_images; index++) {
            squares += locations[index] + squares_array[index] + ">"
        }
        var target = locations[0] + squares_array[0] + ">"
        return [squares, target]
    }

  var memory = {
        type: "html-keyboard-response",
        stimulus: function () { return memory_array(condition)[0] },
        choices: jsPsych.NO_KEYS,
        trial_duration: 200,
    }

    var test = {
        type: "html-keyboard-response",
        stimulus:/* a function call based on the values of memory.stimulus()*/,
        choices: [83, 75],
        trial_duration: 6000
    }

Thanks for the help!

[becky-gilbert]

Hi @idoba2030, one way to do this is to use a global variable to store the current value of your memory array each time it changes in the memory trial, and then in your test trial, access that variable in the stimulus function, like this:

var current_memory_stim = null; // set up a global variable to hold your memory stimulus

var memory_array = function (condition) {
  number_of_images = parseInt(condition[0])
  locations = get_locations(location_names, number_of_images)
  squares_array = get_squares(change_detection_images, number_of_images)
  var squares = '';
  for (index = 0; index < number_of_images; index++) {
    squares += locations[index] + squares_array[index] + ">"
  }
  var target = locations[0] + squares_array[0] + ">"
  // update the value of the global variable each time the memory_array function is called
  current_memory_stim = [squares, target]; 
  return current_memory_stim;
}

var memory = {
  type: "html-keyboard-response",
  stimulus: function () { return memory_array(condition)[0] },
  choices: jsPsych.NO_KEYS,
  trial_duration: 200,
}

var test = {
  type: "html-keyboard-response",
  stimulus: function () {
    // use current_memory_stim to access the memory array from the last trial
    // and use that to generate your stimulus here 
  },
  choices: [83, 75],
  trial_duration: 6000
}

I hope this helps. Feel free to post here if you get stuck!

[idoba2030]

Hey Becky,
It helps a lot.
I wasn't aware of the fact that I can update the values of the global function from within the function.
I thought that the return command is the only communication it has with the environment.

In the end, I found a different solution here at the forum that I hope will work as well.

    var change_detection_images = ['images/squares/black.png', 'images/squares/blue.png', 'images/squares/brown.png', 'images/squares/cyan.png', 'images/squares/green.png', 'images/squares/magenta.png', 'images/squares/orange.png', 'images/squares/red.png', 'images/squares/yellow.png']
    var location_names = ["<img class='a' src=", "<img class='b' src=", "<img class='c' src=", "<img class='d' src="]
    var get_squares = function (images, number_of_images) {
        return jsPsych.randomization.sampleWithoutReplacement(change_detection_images, number_of_images)
    }
    var get_locations = function (location_names, number_of_images) {
        return jsPsych.randomization.sampleWithoutReplacement(location_names, number_of_images)
    }

    var memory = {
        type: "html-keyboard-response",
        stimulus: function () {
            number_of_images = parseInt(condition[0][0])
            change_detection_images = jsPsych.randomization.shuffle(change_detection_images)
            location_names = jsPsych.randomization.shuffle(location_names)
            var squares = '';
            for (index = 0; index < number_of_images; index++) {
                squares += location_names[index] + change_detection_images[index] + ">"
            }
            console.log(squares);
            return squares;
        },
        choices: jsPsych.NO_KEYS,
        trial_duration: 3000,
    }


    var test = {
        type: "html-keyboard-response",
        stimulus: function () {
            if (condition[0][1] == 's') { /* it is the same condition */
                square = location_names[0] + change_detection_images[0] + ">"
            }
            else { /* it is different condition */
                square = location_names[0] + jsPsych.randomization.sampleWithoutReplacement(change_detection_images, 1) + ">"
            }
            console.log(condition)
            console.log(square)
            return square
        },
        choices: [83, 75],
        trial_duration: 6000,
        on_finish: function () {
            condition = jsPsych.randomization.sampleWithoutReplacement(['4same', '4diff'], 1)
            console.log(condition)
            console.log('-----------')
        }

I seem to be getting what I want... I hope it's ok and I can continue to the next challenge with this code :).