jsPsych/docs/plugins/jspsych-video-button-response.md

jspsych-video-button-response plugin

This plugin plays a video and records responses generated by button click. The stimulus can be displayed until a response is given, or for a pre-determined amount of time. The trial can be ended automatically if the subject has failed to respond within a fixed length of time. The button itself can be customized using HTML formatting.

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
sources	array	undefined	An array of file paths to the video. You can specify multiple formats of the same video (e.g., .mp4, .ogg, .webm) to maximize the cross-browser compatibility. Usually .mp4 is a safe cross-browser option. The player will use the first source file in the array that is compatible with the browser, so specify the files in order of preference.
choices	array of strings	[]	Labels for the buttons. Each different string in the array will generate a different button.
button_html	HTML string	'<button class="jspsych-btn">%choice%</button>'	A template of HTML for generating the button elements. You can override this to create customized buttons of various kinds. The string %choice% will be changed to the corresponding element of the choices array. You may also specify an array of strings, if you need different HTML to render for each button. If you do specify an array, the choices array and this array must have the same length. The HTML from position 0 in the button_html array will be used to create the button for element 0 in the choices array, and so on.
margin_vertical	string	'0px'	Vertical margin of the button(s).
margin_horizontal	string	'8px'	Horizontal margin of the button(s).
prompt	string	null	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).
width	numeric	width of the video file	The width of the video display in pixels.
height	numeric	heigh of the video file	The height of the video display in pixels.
autoplay	boolean	true	If true, the video will begin playing as soon as it has loaded.
controls	boolean	false	If true, controls for the video player will be available to the subject. They will be able to pause the video or move the playback to any point in the video.
start	numeric	null	If given a value, the video will start at this time point in seconds.
stop	numeric	null	If given a value, the video will stop at this time point in seconds.
rate	numeric	null	The playback rate of the video. 1 is normal, <1 is slower, >1 is faster.
trial_ends_after_video	bool	false	If true, then the trial will end as soon as the video file finishes playing.
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 timing_response 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
button_pressed	numeric	Indicates which button the subject pressed. The first button in the choices array is 0, the second is 1, and so on.
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.
stimulus	string	JSON encoding of the sources array.

Example

var trial = {
	type: 'video-keyboard-response',
	sources: [
		'video/sample_video.mp4',
		'video/sample_video.ogg'
	],
	choices: ['Happy','Sad','Angry','Peaceful'],
	prompt: '<p>Which emotion the best descriptor of the main character\'s feelings?</p>'
}