UPDATE, NOV 2021

The new and improved version of this plugin, which is compatible with jsPsych 7.0, can be found at https://github.com/jspsych/jspsych-contrib/tree/main/packages/plugin-libet-intentional-binding. I'll leave this version here for now, but the documentation for the new version is much more complete.

Note, May 2023: Two versions of the plugin are now available for compatibility with legacy jsPsych versions 6.1.0 and 6.3.0.

jspsych-libet

A jsPsych plugin for measuring intentional binding using a Libet clock.

Parameters

Parameter	Type	Default Value	Description
cond_bo	string	'baseline'	Specifies whether the condition is "baseline" or "operant"
cond_kt	string	'key'	Specifies whether the condition is "key" or "tone"
tone_file	audio file	undefined	The tone file to be played
hand_est	boolean	true	If true, the participant will produce their estimate by moving the clock hand themselves
instructions	HTML string	''	if hand_est is true, participants will be shown these instructions during estimation

Data generated

Name	Type	Value
keypress_ms	numeric	The time, in milliseconds, at which the participant pressed a key
theta_keypress	numeric	The angle of the clock hand, in radians, when the participant pressed a key
tone_ms	numeric	The time, in milliseconds, at which the tone began to play
theta_tone	numeric	The angle of the clock hand, in radians, when the tone began to play

Examples

Allowing the participant to move the clock hand to estimate the time of a tone

var trial = {
    type: 'libet',
    tone_file: 'tone.mp3',
    cond_bo: 'operant',
    cond_kt: 'tone',
    hand_est: true
};

Trial with written estimate of clock location at time of tone

var trial = {
    type: 'libet',
    tone_file: 'tone.mp3',
    cond_bo: 'operant',
    cond_kt: 'tone',
    hand_est: false
};
var estimation = {
  type: 'survey-text',
  questions: [
    {prompt: "What number was the clock hand pointing at when the tone played?"}
  ],
};