Plugins

In jsPsych, plugins define the kinds of tasks that subjects perform in experiments. Some plugins define very general tasks, like displaying instructions or displaying a visual stimulus and getting a keyboard response. Other plugins are more specific, displaying particular kinds of interactive stimuli, or running a specific version of particular kind of task. Creating an experiment with jsPsych involves figuring out which plugins are needed for the kinds of tasks you want to have your subjects perform.

Plugins provide a structure for a particular task, but often allow for significant customization and flexibility. For example, the jspsych-single-stim plugin defines a simple structure for showing a visual stimulus and collecting a keyboard response. You can specify the what the stimulus is, what keys the subject is allowed to press, and how long the stimulus should be on the screen, how long the subject has to respond, and so on. Many of these content options have reasonable default values; even though the jspsych-single-stim plugin has many different options, you only need to specify the stimulus in order to use it. Each plugin has its own documentation page, which describes what the plugin does and what options are available.

Using a plugin

To use a plugin, you'll need to load the plugin's JavaScript file on your experiment page:

<head>
<script src="jspsych/plugins/jspsych-single-stim.js" type="text/javascript"></script>
</head>

Once a plugin is loaded, you can define a trial that uses that plugin. The following JavaScript code defines a trial using the jspsych-single-stim plugin to display an image file ('images/happy_face.jpg'). This trial uses the default values for valid keys, length of display, and other parameters. You could override these values by adding them to the object.

var single_stim_trial = {
    type: 'single-stim',
    stimulus: 'images/happy_face.jpg'
}

Here's an exampe of overriding the default value for timing_post_trial:

var single_stim_trial = {
    type: 'single-stim',
    stimulus: 'images/happy_face.jpg',
    timing_post_trial: 2000
}

Parameters available in all plugins

Each plugin specifies its own set of parameters. Check the documentation for a plugin to see what parameters are available and what they do.

In addition, there is a set of parameters that can be specified for any plugin.

Parameter Type Default Value Description
timing_post_trial numeric 1000 Sets the time, in milliseconds, between the current trial and the next trial.
on_finish function undefined A callback function to execute when the trial finishes. See this page for more details.
data object undefined An object containing additional data to store for the trial. See this page for more details.
display_element jQuery DOM selection Change the target display at the trial level by specifying a new target for content.

Data collected by plugins

Each plugin defines what data is collected on the trial. The documentation for each plugin specifies what data is collected by that plugin.

In addition to the data collected by a plugin, there is a default set of data that is collected on every trial. The collected data are:

Name Type Value
trial_type string The name of the plugin used to run the trial.
trial_index numeric The index of the current trial across the whole experiment.
time_elapsed numeric The number of milliseconds since the start of the experiment when the trial ended.
internal_node_id string A string identifier for the current TimelineNode.

List of available plugins

This table is a description of all plugins that are currently bundled with jsPsych. Click on the name of a plugin to view its documentation page.

Plugin Description
jspsych‑animation Shows a sequence of images at a specified frame rate. Records key presses (including timing information) made by the subject while they are viewing the animation.
jspsych‑button‑response Present a stimulus and collect a response via the subject clicking a button. The button can be customized extensively (e.g., to use images in place of buttons).
jspsych‑call‑function Executes an arbitrary function call. Doesn't display anything to the subject, and the subject is usually unaware that this plugin has even executed. It's useful for performing tasks at specified times in the experiment, such as saving data.
jspsych‑categorize The subject responds to a stimulus using the keyboard and can be given feedback about the correctness of their response.
jspsych‑categorize‑animation A mash-up of the animation and categorize plugin. The subject responds to an animation and can be given feedback about their response.
jspsych‑free‑sort Displays a set of images on the screen in random locations. Subjects can click and drag the images to move them around the screen. Records all the moves made by the subject, so the sequence of moves can be recovered from the data.
jspsych‑html Displays an external HTML page (such as a consent form) and lets the subject respond by clicking a button or pressing a key. Plugin can validate their response, which is useful for making sure that a subject has granted consent before starting the experiment.
jspsych‑instructions For displaying instructions to the subject.
jspsych‑multi‑stim‑multi‑response A more generalized version of the single-stim plugin. Can display multiple stimuli in a single trial, and collect multiple responses in a single trial.
jspsych‑palmer Shows grid-like stimuli inspired by Stephen Palmer's work. The stimuli are editable: subjects can add and subtract parts interactively. Also contains a method for generating the HTML code to render the stimuli, allowing them to be used in other plugins.
jspsych‑reconstruction The subject interacts with a stimulus by modifying a parameter of the stimulus and observing the change in the stimulus in real-time.
jspsych‑same‑different A same-different judgment task. A stimulus is shown, followed by a brief gap, and then another stimulus is shown. The subject indicates whether the stimuli are the same or different.
jspsych‑similarity Two stimuli are shown sequentially, and the subject indicates how similar they are by dragging a slider object.
jspsych‑single‑audio A basic plugin for playing an audio stimulus and getting a keyboard response.
jspsych‑single‑stim A basic plugin for displaying a stimulus and getting a keyboard response.
jspsych‑survey‑likert Displays likert-style questions.
jspsych‑survey‑multi‑choice Displays multiple choice questions.
jspsych‑survey‑text Shows a prompt with a text box. The subject writes a response and then submits by clicking a button.
jspsych‑text Shows HTML-formatted text on the screen.
jspsych‑visual‑search‑circle A customizable visual-search task modelled after Wang, Cavanagh, & Green (1994). The subject indicates whether or not a target is present among a set of distractors. The stimuli are displayed in a circle, evenly-spaced, equidistant from a fixation point.
jspsych‑vsl‑animate‑occlusion A visual statistical learning paradigm based on Fiser & Aslin (2002). A sequence of stimuli are shown in an oscillatory motion. An occluding rectangle is in the center of the display, and the stimuli change when they are behind the rectangle.
jspsych‑vsl‑grid‑scene A visual statistical learning paradigm based on Fiser & Aslin (2001). A scene made up of individual stimuli arranged in a grid is shown. This plugin can also generate the HTML code to render the stimuli for use in other plugins.
jspsych‑xab A two-alternative forced choice task. A target (X) is shown, followed by a brief gap, and then two choices (A & B) are displayed. The subject must pick whichever one matches X (matches is defined however the experimenter wishes; it could be a literal match, or it could be a match on some particular property).