Fitts Law Web-task

This task is a heavily adapted version of a Fitts Law task from the University of Copenhagen

Setup

• You will need a webserver set-up on your local machine or server.
• Your webserver will need to be able to get PHP files parsed.
• You webserver will need write access to the directory you're serving from.

Operation and configuration

Once you have a webserver succesfully serving the page you will see the index.html file being rendered – this is what participants should be pointed toward.

Once participants have completed the task, their data are POSTed to the finish.php file. This processes the data and writes it to a CSV file, `master.csv' in the root of the serving directory.

If the master.csv file already exists, the new data will be appended to the file.

Pointing a browser at admin.php brings up the admin interface. Here the master.csv file can be downloaded and any existing data wiped.

Note that the master.csv file is not protected from read access in any way; it can be downloaded directly. Wiping of data does required a password, which is hard-coded into admin.php.

js/fitts-law.js

This Javascript file controls the task and the upload of the data from it. The most important configurable aspects of this file relate to the creation of trials:

var conditions = _.shuffle([{
    width: 35,
    distance: 275,
    type: 'experimental'
}, {
    width: 55,
    distance: 275,
    type: 'experimental'
}, {
    width: 35,
    distance: 325,
    type: 'experimental'
}, {
    width: 55,
    distance: 325,
    type: 'experimental'
}]);
conditions.unshift({
    width: 60,
    distance: 200,
    type: 'training'
});

This is programmed with four experimental trials that vary the width of the target and the distance between them. By default lodash.shuffle() is called on these trials so that their order is randomised.

After the experimental trials, a training trial as added to the front of the list of trials. The type property of the trial objects is recorded in a column in the output so that training and experimental trials can be distinguished.

The experiment can be changed by adjusting the width and distance parameters to something else. The current design of experiment is 2x2, with width (35,55) and distance (200,325) being varied. A variety of designs can be created by adjusting these parameters. Note that only one trial of each trial object is set. Therefore, to build a bigger sample, multiple trial objects should be created.

Other configurable parameters can be found throught the file:

 isoParams: {
  num: 9,
  distance: conditions[currentCondition].distance,
  width: conditions[currentCondition].width
 },

Here num is the number of possible targets that appear on the screen at any moment. It is set to 9 by default.

The MAX_TIME constant is a number of milliseconds. Any trials exceeding this time limit will be dropped as outliers (e.g., if a participant got distracted during the trial). The CLICKS_PER_TRIAL' constant represents the number of clicks' in a given task. Note that a first click is required to 'start' the trial, so the number of clicks in each trial is actually CLICKS_PER_TRIAL + 1.

admin.php

The main configuration change that can be made here is to the password. By default the password is 'password' by adjusting the comparison:

$_POST['password'] == 'delete'

And replacing delete with some other string, the password can be changed.

finish.php

You can edit this file to adjust where the master.csv file gets stored and what it is named. Note that if you change the name or path, you will need to update other files – the master.csv filename is hardcoded throughout.