Where in data is post_trial_gap added?

[vchopurian]

Hi!
So I was wondering where the post_trial_gap data is saved? Is it added to the response time in a plugin?

[rbruno1]

post trial gap isn't for collecting data. It is used to change the amount of time between trials

[vchopurian]

Oh, yes I know, but I was wondering whether this gets saved somewhere automatically by jspsych!

[becky-gilbert]

Hi @vchopurian, the post_trial_gap isn't added to the RT, and it isn't saved anywhere in the jsPsych data by default. You can add it to the data in the trial's on_finish function, like this:

var iti = 1200;

var trial = {
  type: 'html-button-response',
  // other parameters...
  post_trial_gap: iti,
  on_finish: function(data) {
    data.post_trial_gap = iti;
  }
}

And as of jsPsych v6.3.0, there's a save_trial_parameters option that you can add to any trial, which lets you automatically save (or not save) any of the trial parameters in the jsPsych data.

var trial = {
  type: 'html-button-response',
  // other parameters...
  post_trial_gap: 1200,
  save_trial_parameters: {
    // save the ITI to the trial data
    post_trial_gap: true
  }
}

This is especially useful when you don't know the value in advance (e.g. because you're using a dynamic parameter to generate different values for each trial):

var trial = {
  type: 'html-button-response',
  // other parameters...
  post_trial_gap: function() {
    // randomly select an ITI from an array of values
    return jsPsych.randomization.sampleWithoutReplacement([200,300,400,500],1)[0];
  },
  save_trial_parameters: {
    // save the ITI to the trial data
    post_trial_gap: true
  }
}

I hope this helps.

[vchopurian]

This is extremely helpful, thank you so much!