jspsych-libet-intentional-binding.md

jspsych-libet-intentional-binding plugin

This plugin measures intentional binding using a Libet clock, and allows the participant to estimate the timing of events by adjusting the clock hand themselves.

Citation

Galang, C. M., Malik, R., Kinley, I., & Obhi, S. S. (2021). Studying sense of agency online: Can intentional binding be observed in uncontrolled online settings? *Consciousness and Cognition*, 95, 103217. doi:[10.1016/j.concog.2021.103217](https://doi.org/10.1016/j.concog.2021.103217)

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. Parameters can be left unspecified if the default value is acceptable.

Parameter	Type	Default Value	Descripton
cond	string	'baseline-key'	Specifies the condition ("baseline-key", "baseline-tone", "operant-key", or "operant-tone").
est_wo_keypress	boolean	false	If true, and if hand_est is true, the participant can make an estimate even if they did not make a keypress during the trial.
tone_file	audio	undefined	The audio file to be played, if applicable.
choices	keys	"ALL_KEYS"	The keys a participant can press, if applicable.
tone_delay_ms	int	250	The time after the key press or the beginning of the clock animation that the tone is played, if applicable.
hand_est	boolean	true	Specifies whether the participant moves the hand to estimate an angle. If false, the trial ends after the clock hand stops spinning.
instructions	HTML string	''	The instructions shown to the participant during estimation, if any.
instructions_wo_keypress	HTML string	undefined	The instructions shown to the participant during estimation if they did not make a keypress. E.g., "When did you feel the urge to make a keypress?". Only applicable if hand_est and est_wo_keypress are set to true. If left undefined, the parameter takes on the same value as instructions.
feedback	boolean	false	If true, and if hand_est is true, the participant sees feedback in the form of a black clock hand pointing in the correct direction.
feedback_ms	int	2000	Number of milliseconds to display feedback, if applicable.
pre_estimation_ms	int	1000	The length of time, in ms, that the clock hand disappears before reappearing to be moved by the participant, if applicable.
hand_inc	float	Math.PI*2/120	The minimum number of radians a participant can rotate the clock hand.
offset_range	float	[Math.PI/4, Math.PI/3]	When the participant is able to move the clock hand, its initial angle will be offset from the correct angle by an absolute amount drawn from this range (in radians). Half the time the initial angle will be offset a positive amount, half the time a negative amount.
fixation_ms	int	400	Duration of the pre-trial fixation cross in ms.
clock_period	int	2560	The period of the clock in ms.
early_ms	int	2560	The earliest allowable keypress, measured in milliseconds since the clock hand begins rotating. If a keypress is made prior to this, the trial ends.
early_fcn	function	function(){}	Function called when the participant responds too early (e.g., to provide feedback).
timeout_ms	int	4000	The maximum length of a trial, measured in milliseconds since the clock hand begins rotating. If a keypress is not made prior to this, the trial ends.
spin_continue_ms	int	1000	The length of time, in ms, after the keypress or tone, whichever comes later, that the clock animation continues.
clock_diam	int	200	The diameter of the clock in pixels.
n_maj_ticks	int	60	The number of major ticks to draw on the clock face.
maj_tick_len	int	12	Length of major ticks in pixels.
maj_tick_start	int	0	Where to draw the first major tick, in radians.
n_min_ticks	int	60	The number of minor ticks to draw on the clock face.
min_tick_len	int	6	Length of minor ticks in pixels.
min_tick_start	int	Math.PI*2/120	Where to draw the first minor tick, in radians.
num	int	[60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5]	The numbers to draw around the clock face.
num_start	int	Math.PI/2	Where to draw the first number, in radians.
num_font	string	"5mm Arial"	The font for the numbers.
num_dist	int	30	Distance of the numbers from the outer circle of the clock, in pixels.
hand_len	int	80	Length of the clock hand in pixels.

Data Generated

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

Name	Type	Value
cond	string	The condition of the trial ("baseline-key", "baseline-tone", "operant-key", or "operant-tone").
early	boolean	Specifies whether the participant pressed a key too early.
timeout	boolean	Specifies whether the trial timed out due to the participant's lack of response.
theta	object	Describes the various important quantities in radians: theta.spin_start: the clock hand begins spinning from this angle theta.keypress: the keypress was made when the clock hand was at this angle theta.tone: the tone began playing when the clock hand was at this angle theta.estimation_start: the clock hand began at this angle during estimation, if applicable theta.target: this is the correct angle for the participant to estimate, given the current condition theta.estimation: this is the estimate provided by the participant, if applicable theta.overshoot: this is the amount by which the participant's estimate overshoots the target angle (where the positive direction is clockwise)

Examples

"Running an operant tone trial"

var trial = {
    type: jsPsychLibetIntentionalBinding,
    cond: 'operant-tone',
    tone_file: 'tone.mp3'
}