webgazer-validate

Current version: 1.0.1. See version history.

This plugin can be used to measure the accuracy and precision of gaze predictions made by the WebGazer extension. For a narrative description of eye tracking with jsPsych, see the eye tracking overview.

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. Other parameters can be left unspecified if the default value is acceptable.

Parameter	Type	Default Value	Description
validation_points	array	[[10,10], [10,50], [10,90], [50,10], [50,50], [50,90], [90,10], [90,50], [90,90]]	Array of points in [x,y] coordinates. The default grid is 9 points. Meaning of coordinates controlled by validation_point_coordinates parameter.
validation_point_coordinates	string	'percent'	Can specify percent to have validation point coordinates specified in percentage of screen width and height, or center-offset-pixels to specify each point as the distance in pixels from the center of the screen.
roi_radius	numeric	200	Tolerance around the validation point in pixels when calculating the percent of gaze measurements within the acceptable range.
randomize_validation_order	bool	false	Whether to randomize the order of the validation points.
time_to_saccade	numeric	1000	The delay before validating after showing a point. Gives the participant time to fixate on the new target before assuming that the participant is looking at the target.
validation_duration	numeric	2000	If calibration_mode is set to view, then this is the length of time to show a point while calibrating. Note that if click calibration is used then the point will remain on the screen until clicked.
point_size	numeric	20	Diameter of the validation points in pixels.
show_validation_data	bool	false	If true then a visualization of the validation data will be shown on the screen after the validation is complete. This will show each measured gaze location color coded by whether it is within the roi_radius of the target point. This is mainly intended for testing and debugging.

Data Generated

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

Name	Type	Value
raw_gaze	array	Raw gaze data for the trial. The array will contain a nested array for each validation point. Within each nested array will be a list of {x,y,dx,dy} values specifying the absolute x and y pixels, as well as the distance from the target for that gaze point.
percent_in_roi	array	The percentage of samples within the roi_radius for each validation point.
average_offset	array	The average x and y distance from each validation point, plus the median distance r of the points from this average offset.
samples_per_sec	numeric	The average number of samples per second. Calculated by finding samples per second for each point and then averaging these estimates together.
validation_points	array	The list of validation points, in the order that they appeared.

Simulation Mode

This plugin does not yet support simulation mode.

Install

Using the CDN-hosted JavaScript file:

<script src="https://unpkg.com/@jspsych/plugin-webgazer-validate@1.0.1"></script>

Using the JavaScript file downloaded from a GitHub release dist archive:

<script src="jspsych/plugin-webgazer-validate.js"></script>

Using NPM:

npm install @jspsych/plugin-webgazer-validate

import webgazerValidate from '@jspsych/plugin-webgazer-validate';

Example

Because the eye tracking plugins need to be used in conjunction with each other, please see the example on the eye tracking overview page for an integrated example.