The Go/NoGo Experiment: A Test of Impulse Control

Source Code for the Go/NoGo Demo

    /* initialize jsPsych */
    var jsPsych = initJsPsych({
      on_finish: function() {
        jsPsych.data.displayData();
      }
    });

    /* create timeline */
    var timeline = [];

    /* preload images */
    var preload = {
      type: jsPsychPreload,
      images: ['img/blue.png', 'img/orange.png']
    };
    timeline.push(preload);

    /* define welcome message trial */
    var welcome = {
      type: jsPsychHtmlKeyboardResponse,
      stimulus: "Welcome to the experiment. Press any key to begin."
    };
    timeline.push(welcome);

    /* define instructions trial */
    var instructions = {
      type: jsPsychHtmlKeyboardResponse,
      stimulus: `
        <p>In this experiment, a circle will appear in the center
        of the screen.</p><p>If the circle is <strong>blue</strong>,
        press the letter F on the keyboard as fast as you can.</p>
        <p>If the circle is <strong>orange</strong>, do not press a key.</p>
        <div style='width: 700px;'>
        <div style='float: left;'><img src='img/blue.png'></img>
        <p class='small'><strong>Press the F key</strong></p></div>
        <div style='float: right;'><img src='img/orange.png'></img>
        <p class='small'><strong>Do not press a key</strong></p></div>
        </div>
        <p>Press any key to begin.</p>
      `,
      post_trial_gap: 2000
    };
    timeline.push(instructions);

    /* define trial stimuli array for timeline variables */
    var test_stimuli = [
      { stimulus: "img/blue.png",  correct_response: 'f'},
      { stimulus: "img/orange.png",  correct_response: null}
    ];

    /* define fixation and test trials */
    var fixation = {
      type: jsPsychHtmlKeyboardResponse,
      stimulus: '<div style="font-size:60px;">+</div>',
      choices: "NO_KEYS",
      trial_duration: function(){
        return jsPsych.randomization.sampleWithoutReplacement([250, 500, 750, 1000, 1250, 1500, 1750, 2000], 1)[0];
      },
      data: {
        task: 'fixation'
      }
    };

    var test = {
      type: jsPsychImageKeyboardResponse,
      stimulus: jsPsych.timelineVariable('stimulus'),
      choices: ['f'],
      data: {
        task: 'response',
        correct_response: jsPsych.timelineVariable('correct_response')
      },
      trial_duration: function(){
        return jsPsych.randomization.sampleWithoutReplacement([3000, 2000], 1)[0];
      },
      on_finish: function(data){
        data.correct = jsPsych.pluginAPI.compareKeys(data.response, data.correct_response);
      }
    };

    /* define test procedure */
    var test_procedure = {
      timeline: [fixation, test],
      timeline_variables: test_stimuli,
      repetitions: 3,
      randomize_order: true
    };
    timeline.push(test_procedure);

    /* define debrief */
    var debrief_block = {
      type: jsPsychHtmlKeyboardResponse,
      stimulus: function() {

        var trials = jsPsych.data.get().filter({task: 'response'});
        var correct_trials = trials.filter({correct: true});
        var accuracy = Math.round(correct_trials.count() / trials.count() * 100);
        var rt = Math.round(correct_trials.select('rt').mean());

        return `<p>You responded correctly on ${accuracy}% of the trials.</p>
          <p>Your average response time was ${rt}ms.</p>
          <p>Press any key to complete the experiment. Thank you!</p>`;

      }
    };
    timeline.push(debrief_block);

    /* start the experiment */
    jsPsych.run(timeline);