jsPsych/docs/markdown_docs/plugins/jspsych-categorize.md

jspsych-categorize

The categorize plugin shows an image or HTML object on the screen. The subject responds by pressing a key. Feedback indicating the correctness of the response is given.

Parameters

This table lists the parameters associated with this plugin. 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
stimuli	array	undefined	Each element of the array is a stimulus. A stimulus can be either a path to an image file or a string containing valid HTML markup. Each stimulus will be presented in its own trial, and thus the length of this array determines the total number of trials.
is_html	boolean	false	If the elements of the stimuli array are strings containing HTML content, then this parameter must be set to true.
key_answer	array	undefined	Each element of the array is a numeric key code indicating the correct response for the corresponding trial. The length of this array should match the stimuli array.
choices	array	undefined	This array contains the keys that the subject is allowed to press in order to respond to the stimulus. Keys can be specified as their numeric key code or as characters (e.g. 'a', 'q').
text_answer	array	""	Array of strings representing a label that is associated with each correct answer. Used in conjunction with the correct_text and incorrect_text parameters.
correct_text	string	"Correct."	String to show when the correct answer is given. Can contain HTML formatting. The special string %ANS% can be used within the string. If present, the plugin will put the text_answer for the trial in place of the %ANS% string (see example below).
incorrect_text	string	"Wrong."	String to show when the wrong answer is given. Can contain HTML formatting. The special string %ANS% can be used within the string. If present, the plugin will put the text_answer for the trial in place of the %ANS% string (see example below).
prompt	string	""	This string can contain HTML markup. Any content here will be displayed below the stimulus. The intention is that it can be used to provide a reminder about the action the subject is supposed to take (e.g. which key to press).
force_correct_button_press	boolean	false	If set to true, then the subject must press the correct response key after feedback is given in order to advance to the next trial.
timing_stim	numeric	-1	How long to show the stimulus for (milliseconds). If -1, then the stimulus is shown until a response is given.
timing_feedback_duration	numeric	2000	How long to show the feedback for (milliseconds).

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.
key_press	numeric	Indicates which key the subject pressed. The value is the numeric key code corresponding to the subject's response.
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	true if the subject got the correct answer, false otherwise.

Examples

These examples show how to define a block using the categorize plugin to achieve various goals.

Categorizing HTML content

// number of trials
var n_trials = 6;

// this is an example of using HTML objects as stimuli.
// you could also use images.
var numbers = ["1", "2", "3", "4", "5"];
var letters = ["I", "Z", "B", "A", "S"];

var stimuli = [];
var answers = [];
var text_answers = [];

// randomly choose stimuli
for (var i = 0; i < n_trials; i++) {
    if (Math.floor(Math.random() * 2) === 0) {
        // pick a number
        stimuli.push("<div id='stimulus'><p>" + numbers[Math.floor(Math.random() * numbers.length)] + "</p></div>");
        answers.push(81);
        text_answers.push("number");
    }
    else {
        // pick a letter
        stimuli.push("<div id='stimulus'><p>" + letters[Math.floor(Math.random() * letters.length)] + "</p></div>");
        answers.push(80);
        text_answers.push("letter");
    }
}

// create categorization block for jspsych
var categorization_block = {
    type: 'categorize',
    stimuli: stimuli,
    key_answer: answers,
    text_answer: text_answers,
    choices: [80, 81],
    correct_text: "<p class='prompt'>Correct, this is a %ANS%.</p>",
    incorrect_text: "<p class='prompt'>Incorrect, this is a %ANS%.</p>",
    is_html: true,
    prompt: "<p class='prompt'>Press P for letter. Press Q for number.</p>"
};