Mouse tracker template

---

This is a template for a mouse tracker experiment. It runs on a minimal set of images randomly selected from MS COCO. The mouse tracker task is inspired by the work from Koenig-Robert et al 2024.

Fill this template with your own experimental parameters to use it. Use the following sections as a guide.

Directory structure

.
├── README.md
├── buttons
│   └── button_styles.css
├── data
│   └── _your data will arrive here_
├── demographics
│   └── demographics.js
├── index.html
├── informed_consent
│   ├── KULeuvenlogo.png
│   ├── informed_consent.css
│   └── informed_consent.js
├── instructions
│   └── instructions.js
├── jspsych-7-pavlovia-2021.12.js
├── list_stimuli.py
├── stimuli
│   └── your main task stimuli here
├── stimuli.js
└── training_stimuli
    └── your training stimuli here

Stimuli

To use your own stimuli, upload images in the stimuli folder. If you want to include some training, include the training images in the training_stimuli folder.

Using your stimuli with jsPsych

To have jsPsych read and use your files, you need to refer to them in your main script. There are two ways of doing so.

1. If you don't have a lot of images, it's probably the easiest to list them inside your index.html, like this: let stimuli = ['./stimuli/image1.png, './stimuli/image2.png', …]
2. In most cases, if you have a lot of images and/or if you want a cleaner script, your can make use of an external .js file. This is in use by default in this template. Such a file should contain a list of stimuli like this:

var training_stimuli = [
  {
    "filename": "./stimuli/image1.png"
  },
  {
    "filename": "./stimuli/image2.png"
  },
  ...
 ]

You can create this external .js file as you please. One way to go about it is illustrated in list_stimuli.py, a python script that will take the stimuli you uploaded in the stimuli folders and automatically create an external .js list for you (see stimuli.js).

About the different folders

• buttons contains a css script to control the appearance of the buttons to press during the mouse tracking task.
• data is where your data will be saved (Pavlovia will drop it there automatically).
• demographics contains an external .js file with the content of the quick demographics survey to appear at the start of the experiment.
• informed consent contains an external .js file with the content of the informed consent participants will accept at the start of the experiment, alongside a .css file to determine some visual features of the consent form.
• instructions contains an external .js file contains instructions to be displayed at different moments of the experiment, and serves to de-clutter the main script.
• stimuli and training_stimuli contain the example stimuli used in the template.

The extra file jspsych-7-pavlovia-2021.12.js comes from this gitlab repository and is the only way around using the readily available jspsych-7-pavlovia-2022.1.1.js which faces consistent issues with terminating the pavlovia connection. It's a temporary solution.

Adapting your own experiment

Parameters

At the top of the script are some global parameters you will need to change in order to adapt the template to your needs. Here is a description of each of them.

Global variables

• exp_online determines if the script initiates a connection with Pavlovia. Switch it to false if you wish to run on your local machine.
• exp_fullscreen determines if the task will enter full screen or not.
• ask_informed_consent determines if an informed consent form appears at the start of the experiment or not.
• ask_demographics determines whether some demographics questions are asked to the participants at the start of the experiment or not.
• exp_instructions determines whether the general instructions are given at the start of the experiment or not.
• exp_training determines whether a training phase is played or not.

Experimental settings

• button_labels are the actual labels on the buttons displayed during the mouse tracker task.
• n_runs determines how many times the full list of main task stimuli is played. Breaks are played in between each run.
• n_blocks determines how many blocks each run will be divided into. Each block is followed by a break and a reversal of the button labels (left and right buttons switch place).
• img_width is the fixed width in pixels of the images you display.
• img_height is commented out by default to not cause aspect ratio transformations in case your images are not of the same size.
• trial_duration is the duration of the full trial, starting from participants pressing the start cross and determining how long a response can be given.
• image_duration is the duration of the image presentation on screen, starting from the beginning of the trial.

Debugging mode

• debugging_mode can be set to true if you wish to drastically reduce the number of trials, both in the training and main task. That can be useful if you want to debug your task.
• debugging_length is the number of trials that you reduce your training and main task to while in debugging mode.

Other things to adapt

Here are some extra things that you might want to adapt in your script.

• The title of your experiment: it will show up as the name of the tab opened in the participant's browser. Change it in the <title> section of your index.html script (line 6).
• The ID of your experiment: optional parameter to record in the data associated with your initJsPsych trial. Give a unique, recognisable ID to easily identify the source of your data once you are playing with your result files (search for the initJsPsych variable).
• The consent form and instructions are left mostly empty and need to be completed.
• The demographics contains some usual questions, but you might want to add or remove some.

Links

Koening-Robert et al 2023, implementation of the mouse tracker.

• Link to the paper
• Link to the repository