Creating stimulus randomly on each trial and evaluating response accuracy at on_finish

[pablobernabeu]

Hello,

I would like to ask for advice on how to create a stimulus randomly (using Math.random) on each trial, and then, at on_finish, evaluating the accuracy of the response to that stimulus. I have been unsuccessful in many attempts at this. I have tried to create and store the stimulus in the data: for the trial, then call ...lasttrialdata.values... or data.random_stimulus in the stimulus parameter, and finally evaluate the accuracy of the response at on_finish, as in the example below:

    var ReadAbil_instructional_manipulation_check = {
      type: jsPsychHtmlKeyboardResponse,
      choices: [' '],
      trial_duration: 10000,
      data: { 
        task: 'ReadAbil_instructional_manipulation_check',
        digits_to_type_in: Math.floor(Math.random() * 100)
        },
      stimulus: digits_to_type_in,
      on_finish: function() {
          /* Categorise passed check */
          if((digits_to_type_in < 50 & data.response == 'f') |
              (!digits_to_type_in < 50 & data.response == 'j')) {
            data.instructional_manipulation_check = 'passed'
          /* Categorise failed check */
          } else {
            data.instructional_manipulation_check = 'failed'
          };
        /* Terminate experiment if two instructional manipulation checks have been failed.*/
        if(jsPsych.data.get().filter({instructional_manipulation_check:'failed'}).count() == 2) {
            jsPsych.endExperiment('<div>Unfortunately, two instructional manipulation checks '+
              'have been failed. Please return to <b>Prolific</b> and click <button>Stop ' +
              'without Completing</button>. Thank you very much.</div>', data)
        }
      }
    };

The problem is that I get undefined displayed on the screen instead of the stimulus. The data side works well, and so does the on_finish side, which successfully categorises the accuracy of the response. The problem is limited to displaying the stimulus.

I couldn't find any fruitful leads among previous questions.

Thank you very much

[ChristopheBossens]

I think the stimulus property takes an HTML string so I'm not sure if you can access data attributes in it. One possibility is to create the random number as a separate variable outside the definition of the trial. That way you can access it everywhere within it:

let number = Math.floor(Math.random() * 100);

var ReadAbil_instructional_manipulation_check = {
  type: jsPsychHtmlKeyboardResponse,
  choices: [' '],
  trial_duration: 10000,
  data: { 
    task: 'ReadAbil_instructional_manipulation_check',
    digits_to_type_in: number 
    },
  stimulus: number ,
  on_finish: function(data) {
      /* Categorise passed check */
      if((number  < 50 & data.response == 'f') |
          (!number  < 50 & data.response == 'j')) {
        data.instructional_manipulation_check = 'passed'
      /* Categorise failed check */
      } else {
        data.instructional_manipulation_check = 'failed'
      };
    /* Terminate experiment if two instructional manipulation checks have been failed.*/
    if(jsPsych.data.get().filter({instructional_manipulation_check:'failed'}).count() == 2) {
        jsPsych.endExperiment('<div>Unfortunately, two instructional manipulation checks '+
          'have been failed. Please return to <b>Prolific</b> and click <button>Stop ' +
          'without Completing</button>. Thank you very much.</div>', data)
    }
  }
};

[pablobernabeu]

Hi Christophe,

Thank you very much! I'm going to check this out this week.

I tried something like this earlier and jsPsych requested a type parameter for the number variable when I added it to the general timeline. Then I added the parameter and it still did not work. Anyway, I'm going to test your suggestion and work through it if necessary.

I'll report back. :)

[pablobernabeu]

Please find my implementation below. Thank you very much for your help, Christophe.

var random_number = {
  type: jsPsychHtmlKeyboardResponse,
  stimulus: '',
  trial_duration: 20,
  choices: 'NO_KEYS',
  on_finish: function(data) {
    data.random_number = Math.floor(Math.random() * (9999 - 1000 + 1) + 1000)
    data.random_position = jsPsych.randomization.sampleWithoutReplacement([0, 1, 2, 3], 1)[0]
  }
};

var ReadAbil_instructional_manipulation_check = {
  type: jsPsychHtmlKeyboardResponse,
  trial_duration: 10000,
  data: { task: 'ReadAbil_instructional_manipulation_check' },
  stimulus: function(data) {
    if(jsPsych.data.getLastTrialData().values()[0].random_position == 0) {
      return '<p>Performance has been low. Please enter the ' +
        '<b>first</b> number in the following sequence: ' +
        '<span style="font-weight:bold;">' +
        jsPsych.data.getLastTrialData().values()[0].random_number + 
        '</span></p>'
      } else if(jsPsych.data.getLastTrialData().values()[0].random_position == 1) {
        return '<p>Performance has been low. Please enter the ' +
        '<b>second</b> number in the following sequence: ' +
        '<span style="font-weight:bold;">' +
          jsPsych.data.getLastTrialData().values()[0].random_number + 
          '</span></p>'
        } else if(jsPsych.data.getLastTrialData().values()[0].random_position == 2) {
          return '<p>Performance has been low. Please enter the ' +
        '<b>third</b> number in the following sequence: ' +
        '<span style="font-weight:bold;">' +
            jsPsych.data.getLastTrialData().values()[0].random_number + 
            '</span></p>'
          } else if(jsPsych.data.getLastTrialData().values()[0].random_position == 3) {
            return '<p>Performance has been low. Please enter the ' +
        '<b>fourth</b> number in the following sequence: ' +
        '<span style="font-weight:bold;">' +
              jsPsych.data.getLastTrialData().values()[0].random_number + 
              '</span></p>'
            }
  },
  on_finish: function(data) {
    // Categorise passed check
    if(data.response ==
        jsPsych.data.get().last(2).values()[0].random_number.toString().charAt(jsPsych.data.get().last(2).values()[0].random_position)) {
          data.instructional_manipulation_check = 'passed'
      // Categorise failed check
      } else data.instructional_manipulation_check = 'failed';
      // Terminate experiment if two instructional manipulation checks have been failed
      if(jsPsych.data.get().filter({instructional_manipulation_check:'failed'}).count() == 2) {
        jsPsych.endExperiment('<div>Unfortunately, two instructional manipulation checks '+
        'have been failed. Please return to <b>Prolific</b> and click <button>Stop ' +
        'without Completing</button>. Thank you very much.</div>', data)
      }
  }
};