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jspsych-iat-image

jspsych-iat-image plugin

This plugin runs a single trial of the implicit association test (IAT), using an image as the stimulus.

Parameters

In addition to the parameters available in all plugins, this plugin accepts the following parameters. Parameters with a default value of undefined must be specified. Other parameters can be left unspecified if the default value is acceptable.

Parameter Type Default Value Description
stimulus string undefined The stimulus to display. The path to an image.
html_when_wrong string <span style="color: red; font-size: 80px">X</span> The HTML to display when a user presses the wrong key.
bottom_instructions string <p>If you press the wrong key, a red X will appear. Press any key to continue.</p> Instructions about making a wrong key press and whether another key press is needed to continue.
force_correct_key_press boolean false If this is true and the user presses the wrong key then they have to press the other key to continue. An example would be two keys 'e' and 'i'. If the key associated with the stimulus is 'e' and key 'i' was pressed, then pressing 'e' is needed to continue the trial. When this is true, then parameter key_to_move_forward is not used.
display_feedback boolean false If true, then image_when_wrong and wrong_image_name are required. If false, trial_duration is needed and trial will continue automatically.
left_category_key string 'e' Key press that is associated with the left_category_label.
right_category_key string 'i' Key press that is associated with the right_category_label.
left_category_label string ['left'] An array that contains the words/labels associated with a certain stimulus. The labels are aligned to the left side of the page.
right_category_label string ['right'] An array that contains the words/labels associated with a certain stimulus. The labels are aligned to the right side of the page.
stim_key_association string 'undefined' Either 'left' or 'right'. This indicates whether the stimulus is associated with the key press and category on the left or right side of the page (left_category_key or right_category_key).
key_to_move_forward array of characters jsPsych.ALL_KEYS This array contains the characters the subject is allowed to press to move on to the next trial if their key press was incorrect and feedback was displayed. Can also have 'other key' as an option which will only allow the user to select the right key to move forward.
trial_duration numeric null How long to wait for the subject to make a response before ending the trial in milliseconds. If the subject fails to make a response before this timer is reached, the subject's response will be recorded as null for the trial and the trial will end. If the value of this parameter is null, then the trial will wait for a response indefinitely.
response_ends_trial boolean true If true, then the trial will end whenever the subject makes a response (assuming they make their response before the cutoff specified by the trial_duration parameter). If false, then the trial will continue until the value for trial_duration is reached. You can use this parameter to force the subject to view a stimulus for a fixed amount of time, even if they respond before the time is complete.

Data Generated

In addition to the default data collected by all plugins, this plugin collects the following data for each trial.

Name Type Value
stimulus string Either the path to the image file or the string containing the HTML-formatted content that the subject saw on this trial.
response string Indicates which key the subject pressed.
rt numeric The response time in milliseconds for the subject to make a response. The time is measured from when the stimulus first appears on the screen until the subject's response.
correct boolean Boolean indicating whether the user's key press was correct or incorrect for the given image.

Examples

var trial_block = {
  type: 'iat-image',
  stimulus: 'img/blue.png',
  stim_key_association: 'left',
  html_when_wrong: '<span style="color: red; font-size: 80px">X</span>',
  bottom_instructions: '<p>If you press the wrong key, a red X will appear. Press the other key to continue</p>',
  force_correct_key_press: true,
  display_feedback: true,
  trial_duration: 3000, //Only if display_feedback is false
  left_category_key: 'e',
  right_category_key: 'i',
  left_category_label: ['OLD'],
  right_category_label: ['YOUNG'],
  response_ends_trial: true
}

var timeline = [];
timeline.push(trial_block);

jsPsych.init({
  timeline: timeline,
  on_finish: function() {
    jsPsych.data.displayData();
  }
});